The invention relates to an add-on system mainly for attenuated total reflectance infrared spectroscopy, which enables time-resolved photochemical in -situ measurements of different sample types.

Background

When characterizing chemical samples, e.g. gasses, liquids or solid samples, infrared (IR) spectroscopy is a highly useful tool, as it gives a unique finger print signature specific for the vibrational levels in the molecules contained in the sample, thus giving a unique IR spectrum for each molecule.

IR spectrometers are available commercially in multiple designs today designed for different types of IR spectroscopy. For measuring different types of IR spectroscopy, add-on cell / equipment is normally bought separately and installed in a standard IR spectrometer. Such an add-on cell / equipment can e.g. provide for Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), or Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy, all of these methods measuring the IR light scattered from the sample, or transmittance IR spectroscopy, where IR light transmitted through a thin sample is measured.

Transmittance spectroscopy requires a delicate preparation of the sample before an IR spectrum can be obtained, whereas DRIFTS requires a less complicated and delicate sample preparation. For both transmittance spectroscopy and DRIFTS, measurement time of 5-30 minutes for obtaining good IR spectra with a low noise level is required. This is a reasonable long time if one wants to measure kinetics in a sample with these IR spectroscopy techniques. The above described add-on cells / equipments are rather expensive experimental equipment to buy as an accessory to an IR spectrometer. Further, in order to obtain a good time-resolution and/or low noise IR spectra, one would often buy a high- quality IR spectrometer, thereby adding further to the cost of equipment. ATR-IR spectroscopy is often used for analysis of the surface of materials and can be particularly interesting in connection with thick or strongly absorbing materials, where transmission spectroscopy cannot be used. ATR-IR is advantageous as it does not require the usual sample preparation of making a powder sample and potassium bromide (KBr) tablet and further provides IR spectra with a low noise level within a significantly shorter time of down to 2-6 seconds. By using ATR-IR spectroscopy, IR spectra of films having a thickness of only a few micrometers can be obtained. This is possible, since an ATR cell/units contains sample securing means, which secures solid and/or powder samples to the ATR- plate in such a way, that there it is intimate optical contact between the sample and the ATR-IR plate in the ATR cell.

ATR-IR spectroscopy is thus a value tool for characterizing in particular solid and/or powder samples at ambient conditions, i.e. room temperature and atmospherically pressure. For spectrometers equipped with an ATR-IR cell, a heating source can further be incorporated in the ATR-IR cell allowing for measurements of the IR spectra at elevated temperatures.

When characterizing chemical reactions, it is desirable to control the atmosphere around the sample or to create a different atmosphere than air in order to get a clear picture of what is really happening during a chemical reaction. Thus, measuring under in-situ conditions is desirable in many cases. Using conventional ATR-IR cells does not allow for direct (possibly time-resolved) in-situ measurements.

Further, the conventional IR cells discussed above do not allow for in-situ photochemical measurements as it is not possible to expose the sample to e.g. ultra violet light during use of the IR cell.

Description of the invention

Disclosed herein is an add-on system for an attenuated total reflectance infrared (ATR-IR) spectrometer, the ATR-IR spectrometer comprising an ATR-IR plate. The add-on system is primarily for an ATR-FTIR cell / spectrometer, but may also be used in a spectrometer measuring Raman, ultra violet (UV), visible spectra or other types of spectra. The ATR-IR plate in the unit comprises a sample surface side whereon a sample, e.g. a gas, a liquid, a powder, a solid sample or sample mixture, can be placed; and a light-illuminating surface side situated on the opposite side of the sample surface side, wherein IR light from the ATR-IR spectrometer illuminating the light-illuminating surface side passes through the ATR-IR plate, the IR light thereby interacting with the sample and wherein IR light is reflected and/or back scattered from the sample passes through the ATR-IR plate and propagates from the light-illuminating surface side thereby being collected by the ATR-IR spectrometer.

In other words, a sample is placed on one side of the ATR-IR plate, i.e. the sample surface side, and IR light from the IR spectrometer illuminates the sample after having traveled through the ATR-IR plate as the IR light hits the ATR-plate from below, i.e. on the light-illuminating surface side. Thereafter, the IR light interacts with the sample and the reflected and/or back scattered light from the sample travels through the ATR-plate again and into the IR spectrometer as it illuminates from the lower side of the ATR-plate, i.e. the light-illuminating surface side.

The add-on system comprises a cap having an ATR-IR plate facing cap surface, wherein, when the ATR-IR plate facing cap surface is placed on the sample surface side of the ATR-IR plate, a sample cavity enclosing the sample is formed between the sample surface side of the ATR-IR plate and the ATR-IR plate facing cap surface of the cap. This sample cavity can be an air tight cavity.

The cap comprises a first cap opening for allowing gas and/or fluids to enter the sample cavity and a second cap opening allowing gas and/or fluids to exit the sample cavity, the first cap opening and the second cap opening being independently sealable.

The cap also comprises cap sealing means positioned on the ATR-IR plate facing cap surface of the cap adapted for providing a tight sealing between the ATR-IR plate facing cap surface and the sample surface side when the cap is placed on the sample surface side and a force is applied to the cap pressing it in a direction towards the sample surface side of the ATR-IR plate . The cap further comprises an additional light source emitting e.g. ultra violet (UV) and/or visible light into the sample cavity for illuminating and/or interact with the sample when the sample is positioned on the sample surface side of the ATR-IR plate. Provision of the add-on system as described above allows measurements of photochemical reactions by IR spectroscopy to be conducted at in-situ conditions. By in-situ conditions is meant conditions other than ambient conditions, e.g. conditions having a different atmosphere than air or a higher/lower pressure and/or a different temperature than room temperature.

Using the add-on system for measurements of IR spectra during a photochemical reaction can be done in an easy operational manner, as it does not require specialized training beforehand in order to use the add-on system. Further, the add-on system is very inexpensive to produce and is applicable for use with a large variety of commercially available ATR-IR cells.

Also, the add-on system according to the above allows for measurements of an IR spectrum at in-situ conditions in a very short time, typically in the order of a few seconds. This allows for measurements of time-resolved in-situ IR spectra whereby a photo-chemically initiate reaction can be following as the reaction occurs.

In one or more embodiments the additional light source is an UV diode. In one or more embodiments, where the additional light source is a diode, the cap further comprises at least one tube containing a cooling liquid for providing cooling to the UV diode. In one or more embodiments the additional light source is an optical fibre connectable to a laser emitting UV, visible, infra red (IR) light or similar. Thereby it is possible to use the same optical fibre for measuring photochemical reactions initiated with light having different wavelengths, e.g. UV, visible or IR light. The optical fibre does thus not need to be changed when a reaction requires a different excitation wavelength in order to start and/or facilitate the reaction.

In one or more embodiments the additional light source is adjustable in height. In one or more embodiments the add-on system further comprises light collecting means for collecting light transmitted, reflected and/or back scattered from the sample after light from the additional light source has interacted with the sample.

One advantage obtained thereby is that it becomes possible to measure two types of optical spectra from the same sample simultaneously under the exact same in- situ conditions by illuminating the sample from below with the IR light for obtaining ATR-IR spectra of the sample at the same time as illumination the sample from above with the additional light source and collecting the reflected and/or back scattered light from the sample again for obtaining e.g. UV and/or visible spectra.

It is also possible to measure the Raman spectra of the sample 'from above' e.g. by using an optical fibre, which - in addition to providing the additional light source to the sample - also collects the back scattered light from the sample. A small microscope objective could also be used as the object from which the additional light source illuminates and which collects the backscattered and/or reflected light from the sample.

Alternatively, a second fibre can be used for collecting the UV and/or visible or Raman back reflected and/or scattered light.

In one or more embodiments the add-on system further comprising a light source containing cavity, wherein the additional light source and/or the light collecting means is containing within the light source containing cavity with a sample facing side through which the light from the additional light source can illuminate and/or interact with the sample and/or light transmitted, reflected and/or back scattered from the sample after light from the additional light source has interacted with the sample can be collected. In one or more embodiments the sample facing side comprises a window made of sapphire, quartz or glass.

In one or more embodiments the cap further comprises focusing means positioned inside the light source containing cavity, wherein the focusing means focuses the additional light source onto the sample and/or collimates light transmitted, reflected and/or back scattered from the sample after light from the additional light source has interacted with the sample. Thereby, the difference in extent of a photochemical reaction as a function of the intensity of the light used for initiating the reaction can be measured.

In one or more embodiments the focusing means is adjustable in height.

In one or more embodiments the add-on system further comprises an outer magnet system encircling the cap in a plane substantially parallel to the plane in which the ATR-I plate lies, wherein, when the cap is placed on the ATR-IR plate, the outer magnet system is adapted for rotating the sample magnet inside the sample cavity. Thereby is obtained that a liquid sample can be magnetically stirred by adding a small magnet inside the sample cavity and rotating the rotating ring. This is highly advantageous if the sample is a heterogeneous solution, which precipitates without some kind of stirring. In one or more embodiments the outer magnet system comprises a magnet cavity with a multiple of electromagnets evenly distributed such that they encircle the cap. In this way, the sample magnet can be rotated without rotating the outer magnet system by alternating the magnetic field of the electromagnets. In one or more embodiments the outer magnet system comprises an outer magnet and means for rotating the outer magnet around the cap.

In one or more embodiments a temperature probe is attached or integrated into the inner surface of the outer magnet system. In one or more embodiments a temperature probe is attached to or integrated into the inner surface of the cap. In one or more embodiments the temperature probe will be able to measure the temperature of the sample.

In one or more embodiments a temperature probe will be integrated into the sample magnet.

In one or more embodiments the cap further comprises sample securing means for securing the sample to the sample surface side such that intimate optical contact between the sample and the first plate surface is obtained, the sample securing means operating independently of the cap sealing means such that the sample securing means can secure the sample by applying a pressure, which is not affected by the pressure used to secure the cap itself. By intimate optical contact is meant that the distance between the sample and the crystal is on the order of 0-5 micrometers, in most cases 0-2 micrometers. This distance is dependent on the wavelength of the light from the spectrometer, the angle which the light from the spectrometer forms with the ATR-IR plate, and the material of the ATR-IR plate, i.e. the refractive index of the crystal material in the ATR-IR plate.

The sample securing means operating independently of the cap sealing means allows for time-resolved in-situ measurements of IR spectra in solid samples without harming the samples, as the sample securing means can secure the sample applying a pressure which is not affected by the pressure used to secure the cap itself. The sample securing means can thus be easily adjusted both before and after the cap has been secured to the unit, as it is operating independently. Having the sample securing means makes the cap highly suitable for measurements of IR spectra of solid - possibly fragile - samples under in-situ conditions.

The sample securing means can e.g. be a screw or a cylinder adjustable in height by e.g. a spring or click system. The important point is that the sample securing means ensures that there is an intimate optical contact between the sample and the ATR-IR plate. If there is not intimate optical contact between the sample and the ATR-IR plate IR spectra of solid samples cannot be measured.

In one or more embodiments the sample securing means is a screw making it operationally easy adjustable in height.

In one or more embodiments the light source containing cavity is integrated into the sample securing means making the cap design compact. In one or more embodiments the cap further comprises a third opening adapted for changing the pressure inside the sample cavity. This allows for evaporation of the sample cavity, for obtaining vacuum conditions inside the sample cavity or for having high pressure conditions during the measurement of IR spectra. In one or more embodiments the cap further comprises a fourth opening and a membrane sealing the fourth opening, wherein the fourth opening is adapted for supplying the sample inside the sample cavity and/or for adding a substance to the sample. This allows for an optimum control of reaction start time, when doing time- resolved IR measurements, as the sample can be secured to the ATR-IR plate and other conditions such as gas atmosphere and temperature can be set before addition e.g. a liquid substance, which reacts with the sample - the reaction between the two substances being the one, which is to be studied with time- resolved IR spectra. Thus, addition of a reactant can be done without changing the in-situ conditions already obtained inside the sample cavity.

In one or more embodiments the cap is made in a material, such as metal or quartz, which can withstand temperatures up to 300 degrees C or above. Thereby time- resolved in-situ IR spectra can be measured at elevated temperatures. In one or more embodiments the cap sealing means is a ring in a high temperature- stable material, such as e.g. Teflon or an elastomer, the ring being positioned on the ATR-IR plate facing cap surface, thereby providing a tight fit between the ATR-IR plate and the cap. An example of a ring is a Kalrez ring, which is stabile up till 310 degrees C. In one or more embodiments, the add-on system further comprises an ATR-IR plate for a unit in a spectrometer, the ATR-IR plate comprising a sample surface side whereon a sample, e.g. a gas, a liquid, a powder, a solid sample or sample mixture, can be placed; and a light-illuminating surface side situated on the opposite side of the sample surface side, wherein IR light from the ATR-IR spectrometer illuminates the light-illuminating surface side, the IR light thereby interacting with the sample and wherein light is reflected and/or back scattered from the sample propagates from the light-illuminating surface side thereby being collected by the ATR-IR spectrometer. When the ATR-IR plate facing cap surface is placed on the sample surface side of the ATR-IR plate, a sample cavity enclosing the sample is formed between the sample surface side of the ATR-IR plate and the ATR-IR plate facing cap surface of the cap. Disclosed herein is also the use of the add-on system according to the above for measuring of in-situ ATR-IR spectre in a spectrometer equipped with an ATR-IR cell.

Disclosed herein is also a method for measuring at least one in-situ measurements in a sample using the add-on system according to the above, the method comprising the actions of a) placing the sample in the add-on system according to the above, the add-on system being positioned in an attenuated total reflectance infrared (ATR- IR) spectrometer comprising an ATR-IR plate with a sample surface side whereon a sample, e.g. a gas, a liquid, a powder, a solid sample or sample mixture, can be placed; and a light-illuminating surface side situated on the opposite side of the sample surface side, wherein IR light from the ATR-IR spectrometer illuminates the light-illuminating surface side, the IR light thereby interacting with the sample and wherein light is reflected and/or back scattered from the sample propagates from the light-illuminating surface side thereby being collected by the ATR-IR spectrometer.

The method further comprises the action of b) illuminating the sample with light from the additional light source; and c) measuring at least one in-situ ATR-IR spectrum with the ATR-IR spectrometer. In one or more embodiments a chemical reaction is photo-chemically initiated in step b) above and the progression of the chemical reaction followed by multiple measurements of the in-situ ATR-IR spectra of the sample according to step c) above.

In one or more embodiments multiple measurements of the in-situ ATR-IR spectra of the sample according to step c) above is conducted under constant illumination of the sample according to step b) above . In one or more embodiments the method further comprising the step of d) measuring at least one UV and/or visible spectrum of the sample using the additional light source.

In one or more embodiments multiple UV and/or visible spectra according to step d) above and multiple measurements of the in-situ ATR-IR spectra of the sample according to step c are measured simultaneously.

Brief description of the drawings

Figure 1 shows a schematic overview of a commercially available ATR-IR cell.

Figure 2 shows a cap of this invention inserted in the commercially available ATR-IR cell of figure 1 .

Figures 3a-f show a first example of a prior art cap primarily for IR measurements on liquid and gas samples in a perspective view (fig. 3b and 3f), a top-view (fig. 3c), a bottom-view (fig. 3d) and in a side-view (fig. 3a and 3e), where it is installed on top of the ATR-IR plate in the ATR-IR cell.

Figures 4a-d show a second example of a prior art cap primarily for IR measurements on solid and powder samples in a perspective view (fig. 4b), a top- view (fig. 4c), a bottom-view (fig. 4d) and in a side-view (fig. 4a), where it is installed on top of the ATR-IR plate in the ATR-IR cell. Figures 5a-d show a third example of a prior art cap primarily for IR measurements on solid and powder samples in a perspective view (fig. 5b), a top-view (fig. 5c), a bottom-view (fig. 5d) and in a side-view (fig. 5a), where it is installed on top of the ATR-IR plate in the ATR-IR cell.

Figures 6a-d show a fourth example of a prior art cap primarily for IR measurements on solid and powder samples in a perspective view (fig. 6b), a top-view (fig. 6c), a bottom-view (fig. 6d) and in a side-view (fig. 6a), where it is installed on top of the ATR-IR plate in the ATR-IR cell.

Figures 7a-b show a fifth example of a prior art cap primarily for IR measurements on solid and powder samples in a perspective view (fig. 7b) and in a side-view (fig. 7a), where it is installed on top of the ATR-IR plate in the ATR-IR cell. Figures 8a-b show a sixth example of a prior art cap primarily for IR measurements on solid and powder samples in a perspective view (fig. 8b) and in a side-view (fig. 8a), where it is installed on top of the ATR-IR plate in the ATR-IR cell.

Figure 9a shows a show a seventh example of a prior art cap primarily for IR measurements on solid and powder samples in an exploded isomeric view, with details on the cap body shown in a side-top view (fig. 9b), a side-bottom view (fig. 9c), a cut-through view along the A-A axis (fig. 9d), and a cut-through view along the B-B axis (fig. 9e), and the sample securing means in a side-bottom view (fig. 9f), a side view (fig. 9g), and a cut-through view along the C-C axis (fig. 9h).

Figure 9i show a specially designed ATR-IR arm fitting with the cap of the invention.

Figures 10a'-g show the sample securing means and different embodiments of the tip/tip plate used in the cap of figures 4-9.

Figure 1 1 shows a first example of in-situ IR spectra measured using a prior art cap of one of the figures 3-9. Figures 12a-c show a second example of in -situ IR spectra measured using a prior art cap of one of the figures 3-9 at varying temperatures.

Figures 13a-c show the integrated absorbance of an IR band in the IR spectra of figures 12a-c.

Figure 14 shows a third example of in -situ IR spectra measured using a prior art cap of one of the figures 3-9. Figure 15 shows a fourth example of in-situ IR spectra measured using a prior art cap of one of the figures 3-9.

Figures 16a-d show a fifth example of in-situ IR spectra measured using the cap of of figures 9a-h with figures 16b-d being zoom in of different frequency windows in figure 16a.

Figure 17 shows a first embodiment of the cap according to the invention seen in a side-view installed on top of the ATR-IR plate in the ATR-IR cell. Figure 18 shows an second embodiment of the cap according to the invention seen in a side-view installed on top of the ATR-IR plate in the ATR-IR cell.

Figures 19-20 show a third embodiment of the cap according to the invention seen in a side-view installed on top of the ATR-IR plate in the ATR-IR cell.

Description of preferred embodiments

In ATR-IR spectroscopy, the IR radiation is passed through an IR transmitting crystal with a high refractive index allowing the radiation to reflect within the ATR element either once (standard ATR) or several times (multi-bounce ATR). The IR radiation from the spectrometer enters the crystal, onto which the sample is pressed, such that the sample is in intimate optical contact with the top surface of the crystal. The IR radiation subsequently reflects through the crystal into the sample, where it interacts with the molecules in the sample. The backscattered IR light is directed out of the crystal and back into the normal beam path of the spectrometer.

By intimate optical contact is meant that the distance between the sample and the crystal is on the order of 0-5 micrometers, in most cases 0-2 micrometers. This distance is dependent on the wavelength of the IR light from the spectrometer, the angle which the IR light from the spectrometer forms with the surface ATR-IR plate, and the material of the ATR-IR plate, i.e. the refractive index of the crystal material in the surface ATR-IR plate.

Pressing the sample onto the ATR element is essential for measuring IR spectra in solid and/or powder samples, as if there is not intimate optical contact, IR spectra of solid and/ powder samples cannot be measured (see the example described in figures 16).

Figure 1 shows a conventional ATR-IR cell 100 having a box 102 containing different optical elements, an opening for IR light propagating towards the sample and an opening for IR light reflected off and/or backscattered from the sample, referred to as 104 and 106, respectively. The ATR-cell 100 further comprises a pressure clamp 108 attached to an arm 1 10 adjustable in height and an ATR-IR plate 200 containing an ATR-IR medium 202 such as diamond, ZnSe, ZnS, Ge, Si, sapphire, KRS-5, silver halides (AgX) crystals, or crystals in similar materials which are transparent in the spectral range of interest and which have a suitable index of refraction.

The ATR-IR plate 200 has two surfaces; a sample surface side 201 on which the sample is positioned, and a light-illuminating surface side 203 situated on the opposite side of the sample surface side 201. IR light from the ATR-IR cell / spectrometer 100 illuminates the light-illuminating surface side 203 and passed through the ATR-IR medium 202 thereby interacting with the sample placed on the ATR-IR plate 200. The IR light 106 reflected off and/or backscattered from the sample 202 is directed out of the ATR-IR medium 202 and propagates from the light-illuminating surface side 203 of the ATR-plate 200 thereby being collected by the ATR-IR spectrometer/cell 100. When measuring IR spectra, the sample 204 is placed on the ATR-IR medium 202 and (if it is solid) pressed by the pressure clamp 108 onto it, such that it is in intimate optical contact, the latter being essential when measuring IR spectra in solid and/or powder samples.

Figure 2 shows a conventional ATR-IR cell 100 where a cap 300 according to the invention is attached. In the following figures different embodiments of the cap 300 are shown in close-up views seen from different angles.

The first example of a prior art cap 300A shown in figures 3a-d is primarily for measurements of liquid samples. The cap 300A comprises an ATR-IR plate facing cap surface 312. When the ATR-IR plate facing cap surface 312 is placed on the ATR-IR plate 200, a sample cavity 302 enclosing the sample 204 is formed between the ATR-IR plate 200 and the ATR-IR plate facing cap surface 312 of the cap 300A.

The cap 300A also comprises three openings; a first cap opening 304, a second cap opening 306, and a third cap opening 308 which are connected to connector tubes 314, 316, 318 thus providing a channel for allowing gas and/or fluids to enter and/or exit the sample cavity 302 and/or for reducing/increasing the pressure inside the sample cavity 302, possibly creating vacuum conditions. Which cap opening 304, 306, 308 and connector tube 314, 316, 318 that is used for allowing gas and/or fluids to enter or exit the sample cavity 302 and which is used for creating vacuum conditions is not relevant, as all three openings 304, 306, 308 and tubes 314, 316, 318 are normally identical in design and function.

Also, one opening can be omitted if it is not necessary to have the option of creating vacuum conditions. The cap 300A further comprises cap sealing means 310 positioned on the ATR-IR plate facing cap surface 312. The cap sealing means 310 can be a Teflon ring or a similar membrane ring, which provides a tight sealing between the ATR-IR plate 200 and the ATR-IR plate facing cap surface 312 when the cap 300A is pressing towards the ATR-IR plate 200. Obtaining a tight fit between the cap 300A and the ATR-IR plate 200 is normally done by adjusting the height of the pressure arm 1 10 and the clamp 108 such that the pressure arm 1 10 and the clamp 108 press the cap 300A down on the ATR-IR plate 200. Alternatively, if the cap 300A is used in a cell with a pressure arm 1 10, external means, not originally part of the cell, can be used.

The cap 300A in figures 3a-d is shaped as a half sphere with the three openings 304, 306, 308 positioned on the upper half of the sphere. Alternatively, the openings 304, 306, 308 can be placed further down towards the ATR-IR plate facing cap surface 312.

The first cap openings 304, 306, 308 are provided with means for independently sealing each opening. This can be in the shape of connector nuts 324, 326, 328 e.g. provided with air sealing means positioned inside the connector tubes 314, 316, 318.

Figures 3e-f show the first example of a prior art cap 300A with a rotating ring 330 positioned around the cap 300A. The rotating ring 330 is connected to a motor 334 through connection means 336, where the motor 334 rotates the rotating ring 330 in a plane substantially parallel to the plane in which the surface ATR-IR plate 200 lies. Attached to the rotating ring 330 is an outer magnet 332. When the rotating ring 330 rotates, the outer magnet interacts with a sample magnet 338 placed inside the sample cavity 302, thereby forcing the sample magnet 338 to rotate inside the sample cavity 302. By using the rotating ring 330 and the magnets 332, 338, the cap 300A can be used for measuring chemical reactions in liquid samples, which require stirring, e.g. a heterogeneous sample, which would otherwise precipitate. The combination of magnet-induced stirring by means of the rotating ring 330 and in-situ conditions provided by the cap 300A further allows for measurement of chemical reactions occurring at conditions which are otherwise experimentally complicated to obtain. Further, the IR spectra can be measured with a very good time resolution in an easy and inexpensive way. As an alternative to a rotating ring with an outer magnet, an outer magnet system comprises a magnet cavity with a multiple of electromagnets (e.g. three, four, five, six or more electromagnets) evenly distributed such that they encircle the cap could also be imagined. The magnetic cavity is in a non-magnetic material.

A temperature probe may be attached or integrated into the inner surface of the outer magnet system and/or integrated into the inner surface of the cap and/or integrated into the sample magnet. The temperature probe may be able to measure the temperature of the sample.

Figures 4a-d show a second example of a prior art cap 300B comprising the same elements as described and shown in connection with the first example of a prior art cap 300A. The cap 300B has a cylindrical shape with a flat top surface pointing away from the ATR-IR plate and the cap openings 304, 306, 308 and connector tubes 314, 316, 318 are located on a side portion of the cap 300B with the cylindrical shape.

Compared to the first example of a prior art cap 300a, the second example of a prior art cap 300B further comprises sample securing means 400 - in this embodiment in the form of a screw 400 - which is adapted for pressing the sample 204 onto the ATR-IR plate 200. This makes the second example of the prior art cap 300B suitable for solid and/or powder samples.

The cap 300B further comprises a bridge 322, which functions as cap securing means 322, as the cap 300B is secured onto the ATR-IR plate 200 by the pressure clamp 108 and the arm 1 10 holding the pressure clamp 108 pressing on the bridge 322.

The sample securing means 400 operate independently of the cap sealing means 322 and can be adjusted in height before and/or after the cap 300B is secured to the ATR-cell 100. This allows for time-resolved in -situ measurements of IR spectra in solid and/or powder samples without harming the samples, as the sample securing means 400 can secure the sample 204 by applying a pressure which is not affected by the pressure used to secure the cap 300B itself. The sample securing means 400 can thus be easily adjusted both before and after the cap 300B has been secured to the unit, as it is operating independently.

The sample securing means can e.g. be a screw (as shown in the figure) or a cylinder adjustable in height by e.g. a spring or click system. The important point is that the sample securing means 400 ensures that there is an intimate optical contact between the sample 204 and the crystal 202 in the ATR-IR plate 200. If there is not intimate optical contact IR spectra of solid and/ powder samples cannot be measured.

An O-ring sealing 320 or similar is positioned inside the screw opening through which the screw 400 penetrates the cap 300B and enters the sample cavity 302 in order to seal the opening and facilitate creation of vacuum and/or a different gas atmosphere inside the sample cavity 302.

The tip 402 of the screw 400 may be exchangeable and can have different designs suitable for different types of samples 204. Different tip 402 shapes can be seen in figures 9a-g. Figures 5a-d show a third example of a prior art cap 300C comprising the same elements as described and shown in connection with the first and second example of a prior art cap 300A, 300B. The difference between the third example of a prior art cap 300C and the second example of a prior art cap 300B is the shape of the cap 300C and the sample securing means 400: The cap 300C has an elongated oval shape to make it suitable for elongated samples and/or elongated ATR-IR cells, where the IR light bounces up and down inside the ATR-IR plate along an elongated path, i.e. multi-bouncing thereby accumulating the IR absorption signal.

The sample securing means 400 in the third example of a prior art cap 300C has a tip plate 404 (instead of the more symmetrically-shaped tip 402 in the second example 300B) in order to match the elongated shape of the ATR-IR plate 202. The screw 400 normally functions such that the tip plate 404 does not rotate when the screw top 410 is rotated around a vertical axis thus adjusting the screw 400 in height. The screw 400 of the second example of a prior art cap 300B may also work in this way or alternatively rotate along with rotation of the screw top 410. A screw of the first embodiment may also be used in connection with the cap 300C of the second embodiment. Further details on the how the sample securing screw 400 may be adjusted in height without rotating is shown in the embodiment of the cap shown in figures 9a-h.

Yet alternatively, the cap 300C may have two screws operating in parallel for adjusting the tip plate 404 in height such that it presses on the sample 204 to obtain intimate optical contact between the sample 204 and the ATR-IR plate 200.

Figures 6a-d show a fourth example of a prior art cap 300D comprising the same elements as described and shown in connection with the first and second example of a prior art cap 300A, 300B. In the fourth example of a prior art cap 300D, the sample securing means 400' is in the shape of a double screw having two elongated bodies 406, 408. When turning the screw top 410, the second body 408 rotates forcing the first body 406 to change its position in height, whereby the sample 204 can be secured to the ATR-IR plate 200. The advantage with this fourth example of a prior art cap 300D is that the screw 400' does not take up space on the top side of the cap 300D and does not require cap securing means 322 as it can be secured to the ATR-cell directly by use of e.g. the pressure clamp 108 attached to the pressure arm 1 10 on the ATR-cell.

Figures 7a-b show a fifth example of a prior art cap 300E comprising the same elements as described and shown in connection with the first and second example of a prior art cap 300A, 300B. In the fifth example of a prior art cap 300E, an additional outer cap 340 is detachably positioned on the outer surface of the cap 300E on top of the sample securing means 400. The outer cap 340 is secured to the cap 300E by securing means (not shown in the figures). Outer cap sealing means, e.g. an O-ring, ensures a tight fit of the outer cap 340 to the cap 300E whereby the sample cavity 302 can be evacuated and/or filled with a gas.

Figures 8a-d show a sixth example of a prior art cap 300F comprising the same elements as described and shown in connection with the first and second example of a prior art cap 300A, 300B. In the sixth example of a prior art cap 300F, the cap securing means 322 are a detachable part of the cap 300F. Outer cap sealing means, e.g. an O-ring ensures a tight fit of the cap securing means 322 to the cap 300F, when the cap securing means 322 are pressed in place over the cap 300F by adjusting the pressure clamp 108 and the adjustable arm 1 10 holding it. Thereby, the sample cavity 302 can be evacuated and/or filled with a gas.

Figure 9a show a seventh example of a cap 300G in an exploded isomeric view (fig. 9a). The cap 300G comprises a first cap opening 304 for allowing gas to enter the sample cavity 302 and a second cap opening 306 allowing gas to exit the sample cavity 302, the first cap opening 304 and the second cap opening 306 being independently sealable by means of the first connector tube 314 / the first connector nut 324 and second connector tube 316 / the second connector nut 326, respectively. The cap 300G also comprises cap sealing means 310 in the form of an O-ring contained inside a recess 31 1 in the ATR-I plate facing cap surface 312. The cap also comprises an additional O-ring sealing 320.

The sample securing means 400" comprises a tip 402 and a screw body 406 and a screw top 410 as shown in details in a side-bottom view (fig. 9f), a side view (fig. 9g), and a cut-through view along the C-C axis (fig. 9h).

The body of the cap 300G is shown in details in a side-top view (fig. 9b), a side- bottom view (fig. 9c), a cut-through view along the A-A axis (fig. 9d), and a cut- through view along the B-B axis (fig. 9e).

The cap 300G also comprises two opposite each other positioned side openings 344. Inside the side openings 344 are placed side screws (not shown in figure). These side screws extend into a screw top recess ring 412 and thereby ensure that the screw top 410 can only rotate in the horizontal plane and not move up or down. The screw body 406 connected to the tip 402 has a slightly elongate elliptical shaped which is mimic by a corresponding shape of the opening in the ATR-IR plate facing cap surface 312 forming the sample cavity 302. This ensures that the screw body 406 and the tip 42 cannot rotate inside the sample cavity 302.

The screw top 410 has an inner cavity 414 with an inner surface thread (not shown in the figures) which the screw body 406 fits into. When the screw top 410 is rotated in the horizontal plane, the inner surface thread forces the screw body 406 with the tip 402 to move up or down (depending on whether it is a clock-wise or counter- clock-wise rotation). In this manner, the tip 402 can secure the sample 204 to the ATR-IR plate 200 without using rotational motion which may squeeze the sample 204 and thereby destroy it. The cap 300G is fixed to the ATR-IR plate 200 by adjusting the pressure clamp 108 and the adjustable arm 1 10 holding it, thereby pressing on top of the sample securing means 400. In this embodiment, the sample securing means 400 and the cap securing means 322 are integrated into one unit, which however still allows for individual adjustment of the pressure applied to the sample and the pressure exerted onto the cap. Alternatively, a bridge as shown in figure 4a could also be included in the cap 300G.

The cap 300 is normally made in a materiel which can withstand temperatures up to at least 300 degrees. Such a material can e.g. be metal, glass, quartz or similar. The sample cavity 302 can optionally be coated on the inside to avoid light from the outside environment to reach the sample cavity 302.

The cap 300 is shown in different shapes and designs in the different embodiments described above. However, it should be understood that the cap 300 can have different shapes, e.g. squared or triangular.

The size of the cap 300 is such that its height fits under the pressure clamp 108 in commercially available ATR-IR cells. The cap 300 can e.g. have a height of 1 -10 cm or 1-5 cm. The sample securing means 400 is in the described embodiments shown as a screw. It should however be understood that alternative options such as a cylinder, which can be adjusted in height by e.g. a spring or click system, could also be imagined. The important point is that the sample securing means 400 ensures that there is an intimate optical contact between the sample 204 and the ATR-plate 200. Otherwise, IR spectra of solid samples cannot be measured.

The cap 300 may comprise yet an additional opening (not shown in the figures) through which a liquid sample or reactant can be added to the sample cavity 302.

Thereby it is possible to measure IR spectra in short time intervals as a chemical reaction occurs still having control of the atmosphere surrounding the sample 204. This is particularly useful when measuring IR of liquid samples, as the opening can be used for supplying the sample itself to the sample cavity 302 and/or for adding a liquid reactant to the sample 204.

The cap 300 may be connectable to a specially designed ATR-IR cap arm 1 100 shown in figure 9i, which is designed such that it either substitutes the existing adjustable arm and the pressure clamp on the conventional ATR-IR cell/unit in the ATR-IR spectrometer or is directly connectable to the existing arm. The ATR-IR cap arm 1 100 is constructed such that when it is connected to the conventional ATR-IR cell/unit in the ATR-IR spectrometer and to any of the caps 300 of the invention described herein, such that the user can move the arm 1 100 and the cap 300 together.

The ATR-IR arm 1 100 comprises one end 1 102, which is connectable to the conventional ATR-IR cell/unit and an opposite end 1 104, which the user fixates to the cap 300. The first end 1 102 is normally connected to a base part (not shown in figure) which in turn is connectable directly to the conventional available ATR-IR cells.

The interface between the ATR-IR arm 1 100 and the base part functions like a pickup on an old record player, where the ATR-IR arm 1 100 can be turned to one side and be lifted up and down. When the ATR-IR arm 1 100 is positioned in the measuring position, a magnet mounted on the base can function such that it is ensured that the cap 300 is positioned directly over the ATR-IR plate. In this way, the ATR-IR arm 1 100 can be moved to the side and back again several times and still be positioned on top of the ATR-IR plate at the same position each time.

On the second end of the ATR-IR arm 1 100, the two 'claws' may have a springs which ensures a quick and easy mounting of the cap 300 in the ATR-IR arm 1 100. Alternative means for fastening the cap 300 in the ATR-IR arm 1 100 could also be imagined.

The ATR-IR arm 1 100 comprises a mount 1 106, which is adapted for inserting different equipment to enhance the functionality of the ATR-IR arm 1 100. Examples of such additional equipment could be a toothed wheel, which would interact directly with the screw top 410, whereby it would be possible to adjust the screw top 410 easily after mounting it to the ATR-IR arm 1 100 and the ATR-IR plate.

A motor incorporated in a toothed wheel placed in the mount 1 106 could also be imagined. The toothed wheel could be a universal cog interface that fits any screw top 410 with a need for rotation. The use of the motor could be set to automatically turn the top 410 and thereby the sample securing means 400 clockwise or counterclockwise so that either the tip 402 is pressed down on the sample 204 and/or to tip 402 is removed from the sample 204 thereby releasing the pressure on the sample. Yet alternatively, the motor could be integrated as a part of the cap itself.

To further automate the ATR-IR cap arm 1 100, a sensor 1 108 can be placed on the ATR-IR cap arm 1 100 - either at the first end 1 102 of the arm 1 100 as shown in figure 9i or at the second end 1 104 of the arm 1 100, where it connects to the cap 300.

When a cap 300 is placed over the ATR-IR plate 200, the sensor 1 108 will then activate the motor and therefore force the sample securing means 400 toward the sample 204 and/or rotate/activate the magnet system if a setup as described in figures 3e-f is used. Furthermore, the sensor 1108 may also deactivate the motor or retract the sample securing means 400 when the ATR-IR cap arm 1100 is lifted. In this way the sensor 1108 functions to give the system information on whether the ATR-IR cap arm 1100 is in an active state/inactive state or moved between these states. The sensor 1 108 can on this account activate the motor (or motors if a multiple is used) accordingly.

Integrated into the ATR-IR arm 1100 can also be a complete 'Plug'n'Play' system, where high temperature quick-connect gas connections, e.g. produced by Swagelok can be placed on the ATR-IR arm 1100 to automatically interact with the connector tubes 314, 316, 318 when the cap 300 is inserted into the ATR-IR arm 1100. The ATR-IR arm 1100 will in this scenario also act as a heat sink for both the gas connections and the motor (if present) to lead heat away and avoid overheating the normally plastic based quick-connect gas connectors.

By using a cap 300 as described above, time resolved IR spectra can be obtained with a time resolution of typically 2-5 seconds.

Figure 10 shows the sample securing means 400, 400'. The tip 402 of the screw 400, 400' may be exchangeable as shown in the figures and can have different designs suitable for different types of samples 204. Different tip 402 shapes are shown in figures 10a-e and different tip plates 404 are shown in figures 10f-g.

The tip 402 and/or tip plate 404 can be constructed in multiple sizes, shapes and materials as illustrated in figures 10d-e and 10g. The part of the tip 402 and/or tip plate 404 which is in contact with the sample can e.g. be a porous ceramic material, an elastomeric material for creating a tip suitable for fragile samples, or metal, quartz, sapphire or similar. An elastomeric buffer layer or a glass fiber layer could possibly be added as an additional layer 412 as shown in figure 10d and 10g. The function of this layer could be to prevent a ceramic tip from cracking during operation. Also an additional layer 412 could allow for improved gas diffusion in the area directly above the sample 204, as the gas may more easily come in contact with the sample in this way. The sample securing means 400 shown in any of the above described embodiments may also comprise a thermometer positioned inside the screw body 406 and/or tip 402 or have the third cap opening integrated into the sample securing means 400by means of a through-going opening. The sample securing means 400 may also have a thermo-electrical element integrated into the screw body 406 and/or tip 402, which allows for a control of the temperature of the sample. This is advantageous if an exothermic or endothermic reaction occurs inside the cell.

The tip 402 may also have a small cavity inside which contains e.g. a catalyst which is pressed onto the sample by means of e.g. a gas pressure, magnetism, and mechanic pressure or similar, thereby initiating and/or speeding up a chemical reaction.

The ATR-cell 100 may be configured to allow for heating of the ATR-IR plate 200, whereby IR measurements of samples at a specific elevated temperature can be performed. With the addition of a cap 300 according to the above described embodiments, in-situ conditions - where the temperature and the gas environment around the sample 204 are controlled - can be performed in an easy way. Figure 1 1 shows the in-situ measurements of C0 ₂ absorption in lysine- functionalized ionic liquid ([N ₆ 66i4][Lys]) and Methionine-functionalized IL ([N ₆ 66i4]Met) exposed to C0 ₂ studied with ATR-FTIR spectroscopy. The ATR-FTIR spectra were recorded using 8 scans with 4 cm ^"1 resolution on a Nicolet iS5 spectrometer equipped with a heatable Pike Gladi ATR diamond cell and a prior art cap 300A according to the first example. It is noted, that a prior art cap according to the other examples could equally well have been used.

Before exposure to C0 ₂ , the samples were outgassed at 80°C in 00mL/min helium (He). Subsequently, a mixture of approximately 60 % C0 ₂ and 40 % helium (He) in a flow of 35 mL/min was applied at room temperature. The (a) spectra shown at the bottom of figure 1 1 show the IR spectra of [N ₆₆₆ i4]Lys after the first exposure to C0 ₂ . Desorption experiments, where He once again is added to the sample are performed at 80°C and the spectra are shown in (b), and the (c) spectra show yet another round of exposure to C0 ₂ . The spectra in (d) are [N ₆₆₆₁₄ ]Met exposed to

C0 ₂ .

The dashed lines 502 are the spectra directly before the experiment, thus before exposure to C0 ₂ in (a) and (c) and before desorption with He in (b), and the dotted lines 504 are the steady state spectra after equilibrium conditions have been achieved. The light grey lines correspond to spectra taken at initial times shortly after initiating the experiment, and the darker grey lines to spectra at a later time in the experiment. The arrow indicates the time progression from the starting condition spectrum 502 to the steady state spectrum 504. The solid black lines in the inset correspond to difference spectra between spectrum of IL before IL and after C0 ₂ exposure.

All the spectra are ATR corrected using commercially available OMNIC software with the assumption that the ATR-IR plate has a refractive index of 1.5.

The spectra shown in figure 1 1 clearly show the reversible C0 ₂ absorption/desorption. In the before absorption spectra of [ ₆ 66i4]Lys seen as the lower dashed line 502 in the (a) experiments, three peaks in the high energy range are observed. The 3360 cm ^"1 band and 3280 cm ^"1 band - marked 506 and 508, respectively, in the inset in part (a) in figure 1 1 - are assigned to amine N-H stretching (v _N-H ) symmetric (sym.) and antisymmetric (asym.), respectively. The third peak observed at 3175 cm ^"1 - marked 510 in the inset in part (a) in figure 1 1 - is the overtone of the asym. O-C-0 stretching of the carboxylate group (vo-c-o,a_ym.)-

The primary band 512 of the carboxylate group is very intense and located around 1588 cm ^"1 . The in-plane N-H bending of the amine group (δΝ-Η,ίρ), can be seen as a very weak band around 1660 cm ^"1 marked as 514 in the figure. During C0 ₂ adsorption, an intense band 516 is formed at 1699 cm ^"1 that can be assigned to Vo-c-o.asym from carboxylic acid dimers. The formation of carboxylic acids is further supported by the appearance of a very broad band peaking around 3200- 3100 cm ^"1 due to carboxylic dimer OH stretching. The band corresponding to out of plane N-H bending (δ _Ν . _{Η οορ} ) located at 844 cm before absorption, disappeared during the C0 ₂ exposure - clearly indicating the simultaneously disappearance of the primary amine groups. The N-H/O-H stretch region seems hard to interpret after the C0 ₂ absorption. However, a closer look at the difference spectrum reveals that both the symmetric and antisymmetric N-H stretchings have disappeared while new bands at 3408, 3318, 3220, 3025 cm ^"1 have appeared. These are primarily overtones from the strong bands of the carboxylic acid and carboxyiate groups. The N-H stretching would be expected to be located at around 3400 cm ^"1 , and thus overlap with the relatively intense overtone from carboxylic acid Vo-c-o.asym -

The (b) and (c) spectra clearly show the reversible desorption and adsorption cycles. By using a prior art cap 300 according to the above described examples, insight into the kinetics of the C0 ₂ chemisorption in amino functionalized IL is, as shown in figure 1 1 , easily obtained.

Figure 12 shows the IR spectra 600 following the dehydration reaction of glucose to form hydroxymethylfurfual (HMF):

The reaction occurs in the ionic liquid 1 -butyl-3methyl-imidazolium chloride ([bmimJCI) in an ATR-FTIR spectrometer using a prior art cap 300 according to the above described examples. The experiments were performed using a Nicolet iS5 spectrometer using a Specac Golden Gate ATR unit with a High temperature diamond ATR-IR plate. The reaction occurs in a thin film with a flow of nitrogen (N ₂ ). Hereby, water can be selectively removed from the reaction while maintaining HMF and glucose in the sample cavity 302. The IR spectra in figure 12 are measured at 140 °C over a time interval of 300 seconds, with the spectrum measured at 0 seconds marked as 602 and the spectrum measured at 300 seconds marked 604. The arrows mark the trend in increase/decrease of the different IR bands as time increases. The time resolution in the experiment shown in figure 12 is 2-3 seconds. This is significantly faster than if the spectra were to be measured with e.g. conventional DRIFTS FT-IR spectroscopy.

The IR band at 1042 cm ^"1 marked 606 in the figure is characteristic of glucose. As is apparent from figure 12, the glucose characteristic band at 1042 cm ^"1 decreases as a function of time while at the same time, new bands around 1510 cm ^"1 (marked 608) and 1680 cm ^"1 (marked 610) increase in intensity. The 1510 cm ^"1 and 1680 cm ^{" 1} bands are characteristic of HMF and is an indication of formation of HMF.

Figures 13a-c show the integrated absorbance of the IR band at 1042 cm ^"1 assigned to glucose as a function of time obtained from IR spectra measured at 80 °C (702 in figure 13a), 1 10 °C (704 in figure 13b) and 140 °C (706 in figure 13c). The decrease in the absorbance mimics the decrease in glucose concentration as glucose is dehydrated thus forming HMF. Note the difference in time scale, mimicking difference in reaction rate dependent on the temperature. In this example, the reaction rate is exponentially dependent on the temperature.

From figures 12-13 it is clear that the dehydration reaction of glucose to form HMF is significantly faster at high temperatures compared to lower temperatures, thus following an Arrhenius trend.

By using a prior art cap 300 according to the above described examples, it is thus possible to measure dehydration reactions at high temperature under a nitrogen atmosphere with an excellent time resolution. The latter option provides a fast way of obtaining Arrhenius plots, which otherwise is a very time-consuming process using conventional IR spectroscopic methods.

Figure 14 shows the in-situ ATR-FNR spectra of silica impregnated with the ionic liquid 1 -butyl-3-methylimidazolium nitrate ([BMI ]N0 ₃ ) 800 thus forming a SILP material (SILP = supported ionic liquids phase). The IR spectra are obtained using a Nicolet iS5 spectrometer equipped with a heatable Pike Gladi ATR diamond ATR-IR unit and a prior art cap 300B according to the second example. The screw 300 inside the cap 300B is used for fixing the SILP to the ATR-IR plate 200, thereby obtaining the necessary intimate optical contact between the sample 204 and ATR- IR plate 200 for measuring of IR spectra is possible. It is noted, that a cap according to any of the other examples could equally well have been used.

During the experiments, the SILP material was exposed to an atmosphere of 2000 vppm NO, 7 v/v % 0 ₂ and 2 v/v % D ₂ 0 in He, thus simulating flue gas. Over a time of 12 hours, the SILP material's reaction with the simulated flue gas atmosphere is clearly seen in the IR spectra in figure 14 as an increase in intensity of the two absorption bands 802, 804 around 1475 cm ^"1 and 1300 cm ^"1 , respectively, both characteristic of DN0 ₃ along with a decrease in intensity of the N0 ₃ ^" characteristic band 806 around 1350 cm ^"1 . This band, which is due to the characteristic N=0 stretching vibration of the symmetric N0 ₃ ^" species, disappears because of the formation of hydrogen bonded complexes with the deuterated nitric acid. The IR spectrum taken at early time is marked 808 and the spectrum taken after 12 hours is marked 810.

By using a cap 300 according to the invention, it is thus possible to measure reactions between SILP materials and flue gas in an easy and carefree manner.

Figure 15 shows the in-situ ATR-FTIR spectra 900 of the catalyst sulfated Zirconium dioxide (Zr0 ₂ ). The IR spectra are obtained using a Nicolet iS5 spectrometer using a Specac Golden Gate ATR unit with a High temperature diamond ATR-IR cell and a cap 300B according to the second example. The screw 300 inside the cap 300B is used for fixing the sulfated catalyst to the ATR-IR plate 200, thereby obtaining the necessary intimate optical contact between the sample 204 and ATR-IR plate 200 for measuring of IR spectra is possible. It is noted, that a cap according to any of the other examples could equally well have been used.

The first IR spectrum 902 is measured at 200 °C in a nitrogen (N ₂ ) flow at 15ml_/min which has equilibrated for 10 minutes. The second IR spectrum 904 is measured at 200 °C with the pressure reduced to 22 mbar for 4 min. The third IR spectrum 906 is measured at 200 C with the pressure reduced to 22 mbar for 6 min. The fourth IR spectrum 908 is measured at 200 ' C with the pressure reduced to 22 mbar for 15 min. Reduction of the pressure in the sample cavity 302 was obtained by using one of the cap openings 304, 306, 308 for creating the near-vacuum conditions inside the cap 300B.

At non-in-situ conditions water will be present in the air surrounding the sample. This will cause the sulfate species on the surface of the Zr0 ₂ catalyst to change its configuration, as it binds strongly with water. Thus, it will be very difficult to obtain accurate IR spectra of the sulfate species on the surface of the Zr0 ₂ , due to the binding of water.

By using the cap 300B instead, it is easy to obtain the in-situ conditions needed for measuring the IR spectra of the dry sulfated Zr0 ₂ catalyst, whereby the IR spectra of the sulfated species can be seen as apparent from figure 15. The IR band around 1625 cm ^"1 (marked 910 in the figure) is characteristic of water and the IR band around 1 1 15 cm ^"1 is characteristic of the water-sulfate species and is seen as a small shoulder on the broader band marked 912 in the figure. Both of these IR bands 910, 912 decrease in intensity as the atmosphere in the sample cavity 302 is reduced and a drier and more clean water-free catalyst is formed. At the same time, the IR band around 1360 cm ^'1 (marked 914 in the figure) increases in intensity. This band is characteristic of the S=0 stretching of the anhydrous sulfate species.

By using a cap 300 according to the above described examples, it is thus possible to measure the IR spectra of sulfated species on a Zr0 ₂ catalyst at 200 ' C in a near- vacuum and/or a nitrogen (N ₂ ) atmosphere in an easy and carefree manner. Figures 16a-d show the in-situ IR spectra 1000 of a copper (Cu) mordenite (zeolite mineral) based catalyst (Cu-mordenite cat), which is typically used for automotive selective catalytic reduction of nitrogen oxides. The spectra are measured at 150 °C using the cap 300G shown in figures 9a-h with figures 16b-d being zoom in of different frequency windows in figure 16a. The tip 402 was coated with a thin layer of quatz wool to increase diffusion during the in-situ IR measurements. The other caps of the invention could also be used for these measurements.

Figures 16a-d show the in-situ IR spectrum of the Cu-mordenite cat heated to 150 C under a flow of air (30 mL/min) and held at this temperature for 30 minutes marked as line 1002. Marked with line 1004 is the in-situ IR spectrum of the Cu- mordenite cat when the flow of air was exchanged with a gas mixture of 1 % ammonia in helium. The sample was monitored by constantly recording spectra and the very high quality spectra shown in figures 16a-d were obtained by taking 64 scans.

Instantaneously the absorption of ammonia was observed on the zeolite surface, giving evidence of absolute no diffusion limitation even though pressure from the screw in the cap was applied. Several new absorption features showed up in the spectrum upon absorption of ammonia: The strong Si-O/AI-0 in the 1 100-1200 cm ^"1 frequency region (see figure 16a) was strongly influenced by absorption of ammonia, showing that ammonia was also being absorbed in the channels within the inside the mordenite crystals. The frequency band at around 1450 cm ^'1 , which is characteristic for ammonium N-H bending, shows the absorption of ammonia on Brensted acidic sites, while bands at around 1280 cm ^"1 , which is characteristic for ammonia N-H bending, shows absorption on Lewis acidic sites. Both these bands appear in the IR spectrum upon exchange of air with ammonia as most clearly seen in the difference spectrum 1008 in figure 16c.

A simulated flue gas containing NO _x species could for instance have been applied to perform mechanistic studies, and to see which kind of ammonia that was preferred in the NO reduction over the catalyst. This information is very important in the more general characterization of surface acidity. Other probes like pyridine or its derivates could likewise have been applied. In the O-H/N-H stretching region there is also very important information. In air several broad bands are present at around 3450 cm ^"1 due to acidic surface hydroxy I groups (see line 1002 in figure 16b). But by absorption of ammonia (line 1004) this signal disappears and two sharp signals at 3250 cm ^"1 and 3300 cm ^"1 appear due to N-H stretching from the absorbed ammonia. A broader band is also sensed below these bands due to ammonium N-H stretching.

Normally change in spectra below 1000 cm ^"1 cannot be investigated with in-situ transmission IR spectroscopy, as most samples have only poor or no transmittance in this region. However this region is very nicely resolved using ATR-FTIR spectroscopy and a cap of the above described examples as seen in figure 16d, which is a unique advantage of this scanning technique and the cap.

In figure 16a is also seen the spectrum of the Cu-mordenite cat placed on the ATR- IR plate before application of pressure by the screw marked as line 1006 showing that no spectrum could be recorded when there is not intimate contact between the sample and the ATR-IR plate.

By using a cap 300 according to the above described examples, it is thus possible to measure the IR spectra as the gas atmosphere around the sample is changed and obtain very accurate spectra in a very short time.

Figure 17 shows a first embodiment of the cap 300H according to the invention seen in a side-view installed on top of the ATR-IR plate 200 in the ATR-IR cell 100. The first embodiment of the cap 300H comprises the same elements as described and shown in connection with the already described examples of the prior art cap 300 (figures 3-10).

In the first embodiment of the cap 300H, the sample securing means 400 is in the shape of a hollow screw with a screw cavity 412 and a sample facing window 414. Inside the screw cavity 412 is a light source, which in this embodiment is an optical fibre 416 secured inside the screw cavity 412 by fibre securing means 417, e.g. a membrane or similar. The light source emits light, which is incident upon a sample 204 when passing through the sample facing window 414. The sample facing window 414 is made in a material, which allows ultra violet (UV), visible and/or IR light to pass through, such as sapphire, quartz or diamond.

By having an additional light source - apart from the IR light in the IR spectrometer - photochemical kinetic measurements can be performed by initiating a chemical reaction by means of the additional light source and subsequently measure the IR spectra at short time intervals. Also, the additional light source may be required not only to start a reaction, but also throughout the entire photochemical experiment.

By using the cap 300H according to the invention, the atmosphere around the sample and/or the temperature of the sample can be controlled, whereby time- resolved in -situ ATR-FTIR measurements can be performed.

The fibre 416 may be a single band or broad band fibre connectable to an external light source such as a laser, a deuterium lamp, a wolfram lamp or a similar lamp. Thereby it is possible to use the same fibre 416 for measuring photochemical reactions initiated with light having different wavelength, e.g. UV, visible or IR light. The fibre does thus not need to be changed when a reaction requires a different excitation wavelength in order to start and/or facilitate the reaction.

In the second embodiment of the cap 300J shown in figure 18, the sample securing means 400 is in the shape of a hollow screw 400 with a screw cavity 412 and a sample facing window 414 like in the cap 300H in figure 17. However, a different light source in the form of a light emitting diode 418 is positioned inside the screw cavity 412, secured inside the screw cavity 412 by diode securing means 420, e.g. a membrane.

The light emitting diode 418 is electrically connected 422a, 422b to an external energy source for facilitating illumination. Around the light emitting diode 418 also cooling means can optionally be provided, e.g. in the shape of a tube with cooling water/air inlet 424a and cooling water/air outlet 424b for cooling the diode. The screw 400 in the first and second embodiment of the cap 300H, 300 J, can also be constructed in a similar manner as the screw 400' in the fourth example 300D with a second body 408 forcing the first body 406 to change its position in height upon rotation of the screw top 410, whereby the sample 204 can be secured to the ATR-IR plate 200. Thereby is obtained a cap having a screw 400' which does not take up space on the top side of the cap and does not require cap securing means as it can be secured to the ATR-cell 100 directly by use of e.g. the pressure clamp 108 attached to the pressure arm 1 10 on the ATR-cell 100.

The additional light source (both of the above described embodiments) may also be included into the screw 400" shown in the seventh example of a prior art cap 300G in such a manner that the screw top 410 may be allowed to rotate without rotating the additional light source. This could be constructed by having the additional light source enter the screw 400" through a hole in the middle having e.g. a lubricated seal allowing for a tight fit of the additional light source inside the screw top 410 at the same time as ensuring that the screw top 410 can rotate in order to regulate the height of the screw body 406 and the tip 402. In order to ensure that the additional light source may be allowed to move up and down (with the screw 400") an extra amount of e.g. optical fiber could be stored inside the screw 400" - possibly being wrapped around or inside the screw body 406. Alternatively, instead of having the additional light source entering through the screw 400, 400' as shown in figures 16 and 17, the cap 300 can be provided with a light source containing cavity 412, which may be stationary and whose function mainly is to hold the additional light source. The light source containing cavity 412 still has a sample facing side through which the light from the additional light source can illuminate and/or interact with the sample 214 inside the sample cavity 302. This is illustrated in figure 19 showing a third embodiment of the cap 300K, wherein the light source is an optical fibre 416 secured to the cap 300K by the cavity 412, which may be a membrane of similar. A magnet ring system as described in connection with the first example in figures 3e-f can also be positioned around the cap 300K as illustrated in figure 20. The rotating ring 400 with the outer magnet 332 is particular useful when measuring on liquid samples, where stirring is needed in order to obtain a reliable IR spectrum.

The additional light source could also enter into the sample cavity 302 through the first, second or third cap opening 304, 306, 308 - possibly by means of a type of screw, which is fixed in the opening 304, 306, 308. This is a solution which could be implemented in any of the described examples or prior art caps 300A-300G and caps of the invention 300H-300K.

The additional light source could also be a two-item component which is connected after the sample has been fixed to the ATR-IR plate 200. The additional light source in any of the above embodiments does not necessarily have to be positioned inside a cavity, but could also be directed directly into the sample cavity. The additional light-source may further comprise light collecting means for collecting light transmitted, reflected and/or back scattered from the sample 204 after light from the additional light source has interacted with the sample 204. This allows for measurements of UV and/or visible spectra of the sample 204 at the same time as measuring IR spectra.

The additional light source (in any of the described embodiments and examples) may also comprise light collecting means for collecting light transmitted, reflected and/or back scattered from the sample after light from the additional light source has interacted with the sample. The light collection means are normally included in the additional light source. Also, the light collecting means could be contained within the light source containing cavity with a sample facing side through which the light transmitted, reflected and/or back scattered from the sample after light from the additional light source has interacted with the sample can be collected.

This allows for measurements of not only the IR spectra after a photochemical reaction has been initiated, but also for the measurement of the Raman, UV and/or visible spectra of the sample at the same time as one measures the IR spectrum of the sample by extracting information obtained by illuminating the sample with the additional light source from one direction at the same time as illuminating the sample with I light from a second direction. The first, second, and third embodiments of the cap 300H, 300J, 300K are like the previous prior art examples of the cap 300A-300G normally made in a materiel, which can withstand temperatures up to at least 300 degrees. Such a material can e.g. be metal, glass, quartz or similar. Also, the sample cavity 302 can optionally be coated on the inside to avoid reflections of light from the light source backscattered from the inside of the sample cavity 302.

It should also be understood that the cap 300H, 300J, 300K can have different shapes, e.g. squared or triangular, and the size of the cap 300H, 300 J, 300K normally is such that its height fits under the pressure clamp 108 in commercially available ATR-IR units. The cap 300H, 300 J, 300K can e.g. have a height of 1 -10 cm. The cap 300H, 300J, 300K may comprise yet an additional opening (not shown in the figures) through which a liquid sample or reactant can be added to the sample cavity 302.

Thereby it is possible to measure IR spectra in short time intervals as a chemical reaction occurs still having control of the atmosphere surrounding the sample 204. This is particularly useful when measuring IR of liquid samples, as the opening can be used for supplying the sample itself to the sample cavity 302 and/or to add a liquid reactant to the sample 204. By using an embodiment of the cap 300 according to the invention, time resolved IR spectra can be obtained with a time resolution of typically 2-5 seconds.

Using a cap 300H, 300 J, 300K according to the invention together with a commercially available spectrometer, photochemical reactions, e.g. in connection with polymer formation, can easily be studied. In the same way photo-catalytic degradation reactions can easily be followed with the cap 300H, 300 J, 300K of the invention. The cap 300H, 300J, 300K according to the invention can easily be used in connection with the AT -IR arm 1 100 described in figure 9i.

In the pharmaceutical industry, new drugs have to go through a series of stress tests before they are put on the marked. Such tests could include testing of the response to high temperatures, the reactivity with air (oxidation or reduction reactions in the drug as a consequence of being in contact with air), and/or response with subjected to UV radiation. Using a cap 300 according to the invention together with a commercially available spectrometer could provide direct information on all of these issues.

The use of any of the embodiments of the cap 300 according to the invention is not limited to the examples described herein, but could also be used for in-situ measurements of the kinetic in heterogen catalytic reactions, characterization of surfaces, e.g. with regard to acid / base characteristic, redox properties, and/or reactions with different probe molecules such as pyridine, carbon dioxide, methanol, hydrogen gas or ammonia possibly at high temperature.

In the food industry, treatment at high temperature is often essential in order for the food product to obtain the right taste, smell and/or texture. There is often a complicated interaction occurring between hundreds of important chemical substances, where obtaining a qualified overview of these reactions can be somewhat difficult. When using a cap 300 according to the invention, the reaction between e.g. amino acids and sugars in food products during heating of these can be obtained at different temperatures as the reaction occurs.

Also in the food industry, many products are heat-treated to ensure the durability of the product. Heat treatment of food products can, however, destroy the taste or produce side products, which may be harmful or just have an unwanted taste. By using a cap 300 according to the invention, the processes can be studied and information about the optimum heating temperature and/or the optimum atmosphere to conduct the heating at (inert atmosphere vs. air for example) can be obtained.

Thus, when using a cap 300 according to the invention, high quality IR spectra are obtainable in a short amount of time even at in-situ conditions, thus providing a very good time resolution option for kinetic measurements.

The use of any of the embodiments of the cap 300 is further highly advantageous compared to use of the commercially available equipment in DRIFTS or transmission IR cells, as the cap 300 is inexpensive to produce and easy to use.

References

100 conventional ATR-IR cell/unit

102 ATR-IR unit box containing optical elements

104 IR light propagating towards the sample

106 IR light emitted/reflected off the sample

108 pressure clamp

1 10 adjustable arm holding the pressure clamp

200 ATR-IR plate

201 sample surface side of the ATR-IR plate

202 ATR-IR medium

203 light-illuminating surface side of the ATR-IR plate

204 sample

300 cap

300A first example of a prior art cap

300B second example of a prior art cap

300C third example of a prior art cap

300D fourth example of a prior art cap

300 E fifth example of a prior art cap

300F sixth example of a prior art cap

300G seventh example of a prior art cap

300H first embodiment of the cap

300J second embodiment of the cap

300K third embodiment of the cap

302 sample cavity

304 first cap opening

306 second cap opening

308 third cap opening

310 cap sealing means, e.g. a Teflon ring

31 1 recess for the cap sealing means

312 ATR-IR plate facing cap surface

314 first connector tube

316 second connector tube

318 third connector tube

320 O-ring sealing 322 cap securing means

324 first connector nut

326 second connector nut

328 third connector nut

330 rotating ring

332 outer magnet

334 motor

336 connection means

338 sample magnet

340 outer cap

342 outer cap sealing

400 sample securing means

400' second embodiment of the sample securing means

402 tip

402a-e different embodiments of the tip

404 tip plate

404a-b different embodiments of the tip plate

406 screw body

408 second screw body

410 screw top

412 screw cavity / light source cavity

414 sample facing window

416 optical fibre

417 fibre securing means, e.g. a membrane

418 light emitting diode

420 diode securing means, e.g. a membrane

422a electrical connection

422b electrical connection

424a cooling water inlet

424b cooling water outlet

500 in-situ ATR-FTIR spectra of C0 ₂ absorption in IL

502 before reaction IR spectrum

504 steady state IR spectrum

506 IR band around 3360 cm ^"1 508 IR band around 3280 cm ^"1

510 IR band around 3175 cm ^"1

512 IR band around 1588 cm ^"1

514 IR band around 1660 cm ^"1

516 IR band around 1699 cm ^"1

518 IR band around 1510 cm ^"1

600 in-situ ATR-FTIR spectra the glucose→ HMF reaction @ 140 °C

602 IR spectrum @ 0 seconds

604 IR spectrum @ 300 seconds

606 IR band around 1042 cm ^"1

608 IR band around 1510 cm ^"1

610 IR band around 1680 cm ^"1

702 integrated absorbance of the IR band at 1042 cm ^"1 @ 80 °C

704 integrated absorbance of the IR band at 1042 cm ^"1 @ 1 10 °C 706 integrated absorbance of the IR band at 1042 cm ^"1 @ 140 °C

800 in-situ ATR-FTIR spectra of SILP in flue gas

802 IR band around 1475 cm ^"1

804 IR band around 1300 cm ^"1

806 IR band around 1350 cm ^"1

808 IR spectrum taken at 0 hours

810 IR spectrum taken after 12 hours

900 in-situ ATR-FTIR spectra of a sulfated Zr0 ₂ catalyst

902 IR spectrum @ 200 °C in a N ₂ atmosphere

904 IR spectrum @ 200 °C, 22 mbar for 4 min

906 IR spectrum @ 200 °C, 22 mbar for 6 min

908 IR spectrum @ 200 °C, 22 mbar for 15 min

910 IR band around 1625 cm ^"1

912 IR band around 1 1 15 cm ^"1

914 IR band around 1350 cm ^"1

1000 in-situ ATR-FTIR spectra of the Cu-mordenite cat @ 150 °C

1002 IR spectrum @ 150 °C in air

1004 IR spectrum @ 150 °C in 1 % NH ₃ /He

1006 IR spectrum without application of the screw in the cap 1008 difference spectrum

1 100 ATR-!R cap arm

1 102 first end of the ATR-IR arm

1 104 second end of the ATR-IR arm

1 106 mount in the ATR-IR arm

1 108 sensor on the ATR-IR arm