The present invention relates to automated sampling apparatuses with moving sampling heads. In particular, the invention relates to a supplementary device, a so-called sampling vessel, which when used together with an automated sampling apparatus with moving sampling head that has a sampling needle makes said apparatus suitable for sampling substance streams flowing in a continuous flow system and thus for the chromatographic analysis of the flow system with no mechanical/electronical/electrical modifications of the apparatus itself. In particular, when the sampling vessel according to the present invention is used with said sampling apparatus, the apparatus also becomes suitable for quantitative chromatographic characterizations of gaseous phase substances of continuous flow systems.

In general, chromatography is an analytic method for the separation of liquid or gaseous phase multicomponent substances. In particular, gas chromatog- raphy is a generally applicable analytic method that can be used for the separation of volatile organic or inorganic compounds resistant to thermal decomposition (being i.e. thermally stable) and thereby to determine their compositions. It is particularly suitable, among others, for detecting e.g. hydrogen, low hydrocarbons and their derivatives, components of air, such as e.g. air pollutants. Its advantages in- elude efficiency, selectivity, low sample requirement, simplicity and also the samples do not get damaged by the separation and hence the analysis can even be continued with a coupled technique (see e.g. gas chromatograph mass spectrometers).

In chromatographic analysis the component(s) of interest is/are usually mixed with a carrier substance (matrix) and flow - optionally continuously - together with the matrix. Thus, in most cases sampling required for carrying out the analysis takes place from a substance stream, the composition of which is varying over time at the location of the sampling, here the substance stream is a gas or liquid stream that is flowing. In order to ensure that the analysis complies with both quantitative and qualitative requirements of chromatography, calibration is neces- sary. This requires taking samples from (i.e. sampling of) a continuously varying material composition.

In particular, in the case of gas chromatography, nowadays the sampling of gas streams with temporally varying composition is typically carried out by fixed volume sample loop rotary gas chromatographic apparatuses having six or more sample paths. In the case of such apparatuses, the continuous gas stream flushes a loop of fixed (given) volume through a multipath valve, wherein to take a sample said loop is rotated at given intervals into the stream of carrier substance used in the analysis by an electric or pneumatic mechanism. Said fixed volume sample loop configuration provides sufficient flushing and at the same time it always ensures that a known/given amount of gas sample is introduced into the gas chro- matograph.

However, the cost of fixed volume sample loop gas chromatographic apparatuses is relatively high, their mechanical design is complicated and thus the probability of their failure is higher.

It is often necessary to assay so-called volatile organic compounds that are in liquid phase at room temperature, often have significant vapor pressure, but are vaporizing/vaporizable. Such assaying is carried out for example during the analysis of substances from static headspace or substances soluble in organic solvents, wherein (complex) systems of smaller or larger volumes are prepared in sample holders according to predefined criteria and then analyzed as to their biological and/or chemical changes and their temporal evolution within a given time interval. For such experiments, so-called automated sampling apparatuses with moving sampling head equipped with a sampling needle - i.e. xyz autosamplers - are used nowadays, by means of which the sampling of separate sample holders can be performed relatively simply and reliably.

The operating principle of xyz autosamplers is the following: a given amount of substance is withdrawn from a sample holder vessel that is suitably positioned and fixed relative to a sampling needle by the (generally cusped/sharp) sampling (injecting) needle that displaces along a predefined path. Then to analyze further the thus obtained sample, said sample is fed into the inlet duct of a dedicated apparatus (e.g. a gas or liquid chromatographic apparatus) by the injecting/sampling needle. The sample holder vessel is usually arranged on a sample holder tray, in a given position of said tray. The sample holder tray is usually a standard accessory of the xyz autosampler or can be obtained separately. At each sampling and discharging, the tip of the sampling needle is located in a well- defined respective spatial point and moves along a predefined path between these two end points. The coordinates of the end points are programmed into the controlling means of the xyz autosampler. A special kind of sampling apparatuses are the so-called robotic arm autosamplers. Here, the needle is located on one end of a robotic arm configured to move between given bounds in at least one spatial direction. Due to their simplicity and easy handling, said xyz autosamplers are used in the analytic labs rather commonly.

For the chromatographic analysis of e.g. a gaseous phase substance, independently of the fact whether the sampling is performed by a fixed volume sample loop gas chromatographic apparatus or an automated sampling apparatus with moving sampling head having a sampling needle, it is a rather important requisite that in each successive sampling precisely the same volume of sample is withdrawn from the gas plenum of the sample holder vessel and introduced into a gas chromatograph. Putting this another way, reproducibility of sampling of the gaseous phase is essential for chromatographic analysis; similar requisites have to be satisfied when a liquid phase is sampled.

In the case of an xyz autosampler, the requisite of reproducibility of fixed volume sampling is satisfied, but the problems of sampling a continuously flowing substance stream and of sampling a composition that is varying or can be varied over time are still not solved. Therefore, when xyz autosamplers available nowadays are used, the chromatographic analysis of gaseous or liquid phase sub- stances after sampling allows merely a qualitative analysis (i.e. a qualitative characterization), but quantitative data related to (i.e. the quantitative characterization of) the substance under study cannot be obtained.

Accordingly, the operation of an average analytic lab may require/requires - depending on the analysis to be carried out and the characterization needed - both a fixed volume sample loop chromatographic apparatus and an xyz autosampler. However, if an xyz autosampler was able to perform sampling of a flowing gas stream with a reproducible volume and a required precision, which are anyway the basis of quantitative chromatographic characterization, most analytic labs could avoid obtaining, using and maintaining two different types of chromatographic systems. This would allow a significant cost saving. Furthermore, different chromatographic analyses could be carried out more flexibly.

Thus, the object of the present invention is to provide a solution that simply, cost-effectively and reliably, as well as without any - i.e. mechanical/electronical/electrical - modifications of the xyz autosamplers themselves enables xyz autosamplers commonly available nowadays to continuously sample flowing substance streams and, hence, to also perform quantitative chromatographic characterization of e.g. gaseous or liquid phase substances.

In our studies, we have come to the conclusion, that this can be achieved by a supplementary device - a so-called sampling vessel - that guides a substance stream to be assayed/sampled, which can equally be a gaseous or liquid substance stream, or a part of it through a specifically configured channel in said device and thereby allows repeated successive samplings of the substance stream by the xyz autosampler. The above object is achieved by providing a sampling vessel according to claim 1 , whose further preferred embodiments are set forth in claims 2 to 9. By using the sampling vessel according to the present invention in combination with an xyz autosampler, said xyz autosampler becomes suitable for sampling a continuously flowing substance stream in harmony with sam- pling methods set forth in claims 10 to 12 and a use defined in claim 13.

Preferably, the sampling vessel according to the invention - in its highly preferred embodiment for sampling a gaseous phase - can be prepared with geometric parameters (outer dimensions, dimensions/design of sampling location, rotation-symmetric shape, etc.) that are identical to those of headspace (HS) chromatography vials used nowadays with xyz autosamplers. Thus, when a gas stream is to be assayed, the sampling vessel according to the invention can simply be used with an xyz autosampler equipped with standard accessories, such as e.g. a sample holder tray with sample receiving holes arranged in columns/rows for receiving the HS vials which is either a standard accessory to the xyz autosampler or can be purchased separately. In particular, if the sampling vessel is inserted into a sample receiving hole of said sample holder tray, a repeated, successive and reproducible sampling of the gas stream to be assayed becomes possible by an xyz autosampler. A combination of the sampling vessel according to the invention and an xyz autosampler (e.g. by using a suitable sample holder tray) is, hence, suitable or can be made suitable for being applied to qualitative and quantitative chromatographic characterization of gaseous phase substances such as hydrogen, low hydrocar- bons and their derivatives, components of air, vaporized volatile organic compounds and liquid phase substances without disassembling or modifying the xyz autosampler.

As it is apparent to a person skilled in the art, if the sampling vessel according to the invention is appropriately positioned and fixed during sampling, it can equally be used with an xyz autosampler without said sample holder tray, too.

In what follows, the invention is discussed in more detail with reference to the attached drawing, wherein

- Figure 1 is a longitudinal sectional view of a preferred embodiment of the sampling vessel according to the invention formed from a block of material;

- Figure 2 is a perspective representation of another preferred embodiment of the sampling vessel according to the invention to be used in practice;

- Figure 2A is section A-A of the device shown in Figure 2;

- Figure 3 is a longitudinal sectional view of the device illustrated in Figure 2; and

- Figure 4 illustrates the results of the gas chromatographic measurements per- formed with a calibrating gas of known composition after having been sampled with the combination of an xyz autosampler and the sampling vessel according to the present invention.

As it is apparent to a person skilled in the art, the sampling needle of a commonly used xyz autosampler and said needle's tip move along a vertical line in the last phase of the sampling. In this movement, it gets from a retracted position to an advanced position, i.e. the tip moves (specifically from top to bottom) from a position that is located far from the sample holder vessel (e.g. a HS vial) storing the gaseous or liquid substance to a predefined point within the sample holder vessel through a sampling opening of the sample holder vessel. From now on, this direction of movement is referred to as 'direction of puncturing'.

Figure 1 illustrates a preferred embodiment of the supplementary device, i.e. a sampling vessel 10 according to the invention. Accordingly, the sampling vessel 10 has a body 12 that extends longitudinally between a first end 22 having a sampling opening and a closed second end (not shown in the drawing). A flow channel 13 is formed in the body 12, said channel 13 extends within the body 12 along a longitudinal direction of the body 12 over a predefined length thereof. The channel 13 comprises an inlet 14 on the body 12 to allow a substance to be sam- pled to enter the channel 13, a sampling segment 17 to sample the substance fed into the channel 13 and an outlet 16 to discharge the substance that had been sampled from the channel 13. At least over a part of its length the sampling segment 17 is formed as a linear, i.e. straight line segment. The inlet 14, the sampling segment 17 and the outlet 16 form a single continuous flow path within the body 12 in the form of the channel 13; when sampling takes place from the sampling vessel 10, the gas or liquid phase substance to be sampled flows through this flow path continuously from the inlet 14 to the outlet 16. The inlet 14 and the outlet 16 are arranged on the body 12 so as to ensure a substance flow within the sampling segment 17 in a direction opposite to the direction of puncturing, i.e. from the se- cond end of the body 12 to the first end 22 of the body 12. Such an arrangement of the inlet 14 and the outlet 16 facilitates that the tip of the needle of the xyz autosampler is surrounded by the material composition to be assayed when the needle reaches the sampling segment 17, i.e. substantially right after the puncturing performed by the needle. In particular, in the embodiment of the sampling ves- sel 10 according to the invention shown in Fig. 1 , the inlet 14 is located farther from the first end 22, while the outlet 16 is located closer to the first end 22. The inlet 14 and the outlet 16 are configured to receive external ducts for material transport. That is, they are optionally equipped with connections of suitable dimensions/geometry or formed as connections protruding outwards from the body 12 or configured to receive connectors disposed on the ends of said external ducts.

The sampling vessel 10 further comprises a needle guiding channel 15. The needle guiding channel 15 starts from the first end 22 of the body 12 and terminates at the channel 13, more specifically in the sampling segment 17. The needle guiding channel 15 and the sampling segment 17 are positioned preferably coaxially within the body 12. Optionally, the needle guiding channel 15 has got a slightly tapering conical design in the direction of the sampling segment 17, however, this is not necessary; the needle guiding channel 15 can also be formed in the body 12 as a channel with constant diameter along its length. In the latter case, due to manufacturing purposes, the transversal dimension of the sampling segment 17 and that of the needle guiding channel 15 in a plane substantially perpendicular to the longitudinal direction of extension of the body 12 (i.e. their cross sections) preferably correspond to each other. Nevertheless, a needle guiding channel 15 tapering towards the sampling segment 17 is more preferred, because it facilitates a nondestructive insertion of the needle of the xyz autosampler into the sampling segment 17. The needle guiding channel 15 and the sampling segment 17 are of circular cross-section in general, but this is not necessary either: said cross-sections can be of any curved (e.g. elliptic) or rounded-off polygonal shape that, during making use of the sampling vessel 10, impede/influence the substance stream flowing in the sampling segment 17 to the least possible extent. Accordingly, the sampling segment 17 can easily be flushed by the substance flow. Furthermore, the sampling segment 17 provides a constant flow rate in its straight segment over time. Preferably, the full length of said sampling segment 17 is between at least 15 mm and at most 45 mm, while the length of its straight segment is preferably between at least 15 mm and at most 25 mm, more preferably it is about 20 mm. It should be noted, that the sampling segment 17 according to the aforementioned description and its straight segment constitute major part of the sampling vessel 10, as every sampling accomplished by the sampling needle of an xyz autosampler - always performed reliably in a reproducible manner - takes place from this portion of the sampling vessel 10.

Typically, the inner diameter of the needle guiding channel 15 at its narrowest portion is configured to have at least a size that allows the sampling needle of the xyz autosampler that intends taking a sample from the sampling vessel 10 to pass through the needle guiding channel 15, with some clearance, unobstructedly. If the needle guiding channel 15 has a tapered conical design, the inner diameter of the needle guiding channel 15 at its first end 22 can be preferably even as large as 8-10 mm. In this way, the sampling needle of the xyz autosampler can efficiently enter the sampling segment 17 during sampling even if positioning of said sam- pling vessel 10 is less precise. The inner diameters of the inlet 14, the sampling segment 17 and the outlet 16 are preferably between 1 mm and 6 mm, more preferably between 1 mm and 4 mm, even more preferably 1 -3 mm, most preferably between 1 mm and 1 .4 mm. The minimum size of the inner diameter of the sam- pling segment 17 is defined by the outer diameter of the sampling needle of the xyz autosampler; thus, said diameter can be reduced even to about 0.8 mm. At the same time, the size of the inner diameter of the sampling segment 17 is limited from above by the fact that during a continuous sampling process the length of the time period used for flushing when the sampled substance stream (e.g. gas or liquid, especially gas) is changed and thus the waste space of the sampling vessel 10 should be kept as low as possible.

The opening of the needle guiding channel 15 at the first end 22 of the body 12 is sealable in a gastight manner. This is achieved by a closing means 24 that can be arranged on the end 22. Said closing means 24 can be punctured by a sharp/cusped needle-like device - here, by the sampling needle of the xyz autosampler - if a force of a given magnitude is applied to said needle-like device. However, when the force ceases, i.e. upon removal/withdrawal of the needle-like device from the closing means 24, said closing means 24 provides gastight seal- ing again. Said closing means 24 is preferably provided by a septum known to a person skilled in the art. In the sampling vessel 10 according to Fig. 1 , the closing means 24 can be fixed in a seat 25 formed by a recess at the end 22. Depending on the material of the body 12, its end 22 and the closing means 24, the fixation can be achieved in a number of different ways, by means of e.g. gluing, form fitting through pressing and other techniques suitable for fixing the closing means 24 within the seat 25 (optionally, e.g. by using a cap on the end 22). Fixation of the closing means 24 can be both releasable or unreleasable; in the latter case, the closing means 24 is not replaceable, and thus its deterioration limits repeated usability of the sampling vessel 10.

In a preferred embodiment of the sampling vessel 10 according to the invention, the external dimensions of said sampling vessel 10 are selected substantially in conformity with the xyz autosampler, more specifically with a sample holder tray thereof, which the sampling vessel 10 is intended to be used in combination with. In particular, the sampling vessel 10 has an external shape that is comple- mentary to the internal shape of the sample receiving holes of the sample holder tray used with the autosampler to be used for sampling. In order that the sampling vessel 10 according to the invention could be used in standard sample holder trays together with e.g. commonly used HS vials, the length of the body 12 be- tween the first and second ends is about 71 -101 mm, preferably about 75 mm, the outer diameter of the body 12 is about 23 mm and (in the present case) the distance between the inlet 14 and the second end of the body 12 is at least about 22 mm. A minimum value of said length is determined by the fact that sufficiently long sampling segment is desired, while the upper limit of the length is defined by the given arm height of xyz autosamplers used nowadays; said autosamplers cannot be used with HS vials or sampling vessels 10 higher than 101 mm.

Furthermore, preferably the body 12 is cylindrical in shape, but this is not necessary: the outer contour of the body 12 in cross-sectional view can be of arbi- trary shape that matches the shape of the sample receiving holes formed in the sample holder tray. The sampling vessel 10 can be made of any suitable material, e.g. the body 12 can be made of Teflon, glass, a variety of plastics or even stainless steel.

As it is apparent to a person skilled in the art, the channel 13 and its parts, as well as the needle guiding segment 15 can be formed by means of mechanical machining (e.g. drilling, cutting, lathe machining, etc.) the body 12. However, said body 12 having the channel 13 and the needle guiding segment 15 extending in it can also be prepared by e.g. (lost core) injection molding.

Figures 2, 2A and 3 illustrate schematically a sampling vessel 10' repre- senting a possible further exemplary embodiment of the supplementary device according to the invention in different views. As far as its construction is concerned, sampling vessel 10' is reasonably similar to sampling vessel 10 shown in Fig. 1 . Accordingly, in Figures 2, 2A and 3, similar/identical structural elements are denoted by identical reference numbers and, in what follows, are not discussed in detail.

The body 12 of the sampling vessel 10' is formed by a hollow bottle, said bottle is preferably prepared from a HS vial, preferably by means of glass-making techniques. Therefore, the height of the hollow bottle constituting said body 12 is about 71 -101 mm, preferably about 75 mm, while its dimension substantially transversally to its height, preferably its outer diameter, is about 23 mm. As a result, the sampling vessel 10' can be used with any xyz autosampler suitable for taking samples from HS vials. The first end 22 of the body 12 is provided with a thread on its external surface. Thus, a gastight sealing of the body 12 and a displacementless fixation of the septum 24 in a suitable septum seat on the first end 22 is achieved by a cap 18 in this embodiment. The cap 18 that includes on its inner surface a thread mating with the thread of the end 22 comprises a bore 19 in its top which allows the sampling needle of the xyz autosampler to enter the nee- die guiding segment 15 and then the sampling segment 17 through the needle guiding segment 15. Hence, the diameter of the hole 19 can vary between wide limits, its size is chosen preferably in such a way that the sampling needle of the xyz autosampler can easily pass through said hole 19 even if the positioning of the sampling vessel 10' is less precise. In particular, the diameter of the hole 19 is about 10 mm or less. In use, the gastight sealing of the hole 19 is achieved by a closing means 24 provided by a septum in this case by tightly screwing the cap 18 onto the first end 22 of the body 12 and thus keeping the septum in its place on the first end 22 all the time. Here, the channel 13 extending within the body 12 between an inlet 14 and an outlet 16 configured as external connections and, hence, the sampling segment 17 constituting a part of it and the needle guiding segment 15 are formed by a glass pipe welded into the inner space of said 12 body. The inner diameter of said glass pipe is at most a few millimeters, and to optimize the waste space as discussed previously, it is preferably between 0.8 mm and 1 .4 mm in a portion thereof adjacent to the sampling segment 17; for simplifying forming, in the embodiment of the sampling vessel 10' shown in Figure 2, the outlet 16 opens from the needle guiding segment 15. In this embodiment of the sampling vessel 10', said outlet 16 is formed closer to the first end 22, while said inlet 14 is formed farther from said first end 22. In order to maintain in use a substance flow in the sampling segment 17 with a flow direction opposite to the direction of puncturing, i.e. from the second end of the body 12 towards the first end 22 of the body 12 in this case, which - according to our studies - is highly preferred from the point of view of the sampling, the channel 13 has got a U-shaped section between the inlet 14 and the outlet 16 and the sampling segment 17 is provided in a leg of the U- shaped section located adjacent to the outlet 16, i.e. in that leg which is in direct communication with the outlet 16.

The body 12 and the channel 13 of the sampling vessel 10', as well as the inlet 14 and the outlet 16 are made of glass, therefore they are easy to clean and sufficiently inert. As the cap 18 is not in direct contact with the gas flowing through the sampling vessel 10', it can be made of any material acceptable in the field; the material of the cap is preferably polypropylene (PP). However, it is apparent to a person skilled in the art that said parts of the sampling vessel 10' can be made of any other suitable materials, e.g. a variety of plastics or even stainless steel.

As it is also apparent to a person skilled in the art, the sampling vessel 10,

10' according to the present invention can also be used, besides sampling the gaseous phase substances, for the sampling of a liquid phase substance by means of automated sampling apparatuses with moving sampling heads having sampling needles - along with, of course, redesigning the channel 13 in conformity with e.g. the viscosity of the liquid phase substance to be sampled if necessary.

EXAMPLE

In gas chromatographic analyses, the system used for taking and introducing a sample always has to provide linearity, reproducibility and precision. In order that an xyz autosampler could be used as a sampling device for qualitative and quantitative gas chromatographic characterizations with the sampling vessel 10, 10' according to the present invention, the xyz autosampler has to meet the three requisites.

In the present example it has been studied whether these requisites are satisfied if a suitable gas mixture is made to flow through the sampling vessel 10, 10' according to the invention meanwhile samples are taken from the sampling segment 17 of said sampling vessel 10, 10' by a Combi Pal type xyz autosampler manufactured by the company CTC (Zwingen, Switzerland). As a gas mixture, a mixture of methane, ethane and ethylene mixed in the ratio of 1 :1 : 1 (the test gas) was used, and to create a varying gas composition inert nitrogen gas (the diluting gas) was used. To provide a gas mixture of a desired composition, the ratio of the test gas relative to the diluting gas was set/controlled by flow measuring devices. The results obtained in this way are summarized graphically in Fig. 4.

To test the linearity, the linear behavior of a given amount of gas sampled from the gas mixture and fed into the sampling port of a chromatograph has been studied over the injecting range (in particular, within the range of 0.25 to 2 ml) of the selected xyz autosampler, i.e. the peak areas obtained when measuring successive gas samples have been recorded over said injecting range. By a graphical representation of the obtained results and by means of evaluating the measurement data by the technique of least squares, it has been concluded that linearity is met for all three components of the gas mixture with a regression coefficient of at least R ² =0.99. Consequently, linearity of the sampling vessel 10, 10' according to the invention clearly satisfies the requisite required from the point of view of analytics.

To test the precision of the sampling vessel 10, 10' according to the invention, a large number of samples with the volume of 0.25 ml each was taken from the sampling vessel 10, 10' and injected into a gas chromatograph by the previ- ously used xyz autosampler. After this step, the measurement data were subjected to statistical analysis. As a result, it has been received that the standard deviations of the peak areas for the components of the gas mixture obtained by the chromatograph when the sampling vessel 10, 10' has been used are 0.887%, 0.988% and 0.653% for methane, ethane and ethylene, respectively. Since each of these values is smaller than a threshold value of the measurement precision defined usually as 1 %, it can be concluded that the precision of the sampling vessel 10, 10' according to the invention also meets the requisite required from the point of view of analytics.

Finally, the reproducibility of sampling performed by a sampling system formed by a combination of the sampling vessel 10, 10' according to the invention and the xyz autosampler has been studied. To this end, a large number samples with the volume of 0.25 ml each was taken and injected into a gas chromatograph, and then the obtained measurement data have been subjected to a two-sided F- test. As the critical F-value of 3.13 corresponding to the measurement parameters has not been exceeded for any of the components of the gas mixture (the obtained values were 2.201 , 2.399 and 2.626 for methane, ethane and ethylene, respectively), the reproducibility of sampling effected by the xyz autosampler provided with the sampling vessel 10, 10' is considered acceptable.