The invention relates to an extractor of non-volatile organic compounds from a solid matrix.

To extract from solid matrices, such as e.g. loams, non-volatile organic compounds contained in it, i.e. an analyte like e.g. mineral oils, special extractors are used in which a solvent acts, e.g. hexane.

The classic Soxhlet model ( 1879), despite the age and the modest cost, provides excellent results but suffers from long extraction times (approximately 8 hours for 30-40 cycles), hardly bearable in modern analytical laboratories.

Another model 10, more recent and different in concept, is shown in Fig. 1. It includes a lower chamber 20 containing a solvent 22, an intermediate chamber 30 containing a solid matrix 32 (the sample) and an upper condensation chamber 36 containing a condenser coil 38. The two chambers 20, 30 are communicating through a Teflon filter 40. The bottom of the chamber 20 is inserted into a basin 24 having both internal cavities 26, in which cooling water can circulate, and heating means 28 for heating the solvent 22.

At the beginning of a cycle the solvent 22 is heated to make it gaseous and let it go through the filter 40 so as to go through the matrix 32 and reach the chamber 36, where it condenses and falls as rain on the matrix 32. Reached the thermodynamic equilibrium, at which now very little solvent passes from the chamber 20 to the chamber 30, the means 28 are turned off and the basin 24 is cooled via water circulation in the cavities 26. The solvent in the chamber 30 then falls again into the chamber 20 washing the matrix 32, and the cycle starts again.

This system has three major drawbacks. First, it is not fast, because the cycles of heating/cooling the basin 24 take a long time due to its thermal inertia. Second, it is difficult to place various extractors in parallel because the basin of one thermally influences the basin of another. Third, the cost is quite high, especially due to the basin 24, which has a complex structure.

There is then the problem of making an extractor of the above type which is faster (with shorter cycle), cheaper and easier to build.

An extractor as defined in claim 1 solves at least one of the mentioned problems.

An extractor is claimed of non-volatile organic compounds from a solid matrix, comprising

- a heatable chamber for containing and heating a solvent (heating means can be comprised in the heatable chamber or can be external);

- an extraction chamber for containing the solid matrix,

the two chambers being communicating through a septum permeable to the solvent's vapor,

characterized in that the heatable chamber comprises a controlled- opening venting means or vent for lowering, during use, the gaseous pressure of the solvent.

The vapor pressure of the solvent in the heatable chamber allows the accumulation of condensed vapor in the extraction chamber. The pressure drop, better if sudden, draws from the extraction chamber, e.g. for gravity force no longer compensated, the condensed vapor that has washed the solid matrix. The displacement of the condensate is very fast, faster than that in fig. 1, and it is not necessary to vary the temperature of the heatable chamber or cool it. Not only the extraction cycle is much shorter, but the heatable chamber has simpler and more economic structure.

Moreover, during the extraction phase the solvent is kept hot at boiling point by the over-heated vapors rising from the heatable chamber, which can be kept at a temperature considerably higher than the boiling temperature due to the over-pressure generated by the very structure of the device.

The septum is preferably a porous septum (e.g. made of glass or sintered steel), to support the sample, to let the vapor of solvent pass through but to sufficiently retain the condensed liquid with the analyte. A thick metal net or a removable cellulose, Teflon or fiber-glass filter can be used as well.

The vent can disperse the vapor of solvent to the external environment, or recovery it somewhere. Advantageously another washing phase for the matrix can be activated with hot vapor if the extractor comprises as a vent a fluid communication conduit between the two chambers. The vapor from the heatable chamber is unleashed in the extraction chamber, condenses and again washes the matrix, and then percolates with the solute back into the heatable chamber through the septum. The conduit can be an external tube to the chambers, eg. made of silicone, or preferably Teflon, metal, glass, viton or plastic to prevent contamination of the solvent.

The vent or the duct, to improve automation of extraction cycles and the repeatability of performances thereof, can comprise means for controlling on command the vent and/ or the down-flow of fluid. The adjustment can also be uncontrolled, i.e. take place spontaneously eg. if the solvent vapor pressure exceeds a threshold value and makes a diaphragm open. Preferably the adjustment of the fluid (vapor) is controlled, i.e. with a value or instant settable by the user. The means for controlling can be a valve whose opening is driven by

- a timer or

- a signal of a gaseous pressure sensor present in the heatable chamber, or a valve (eg. a tap-valve) operable manually, or

- another sensor that monitors another variable into the extractor

(see below).

So the extractor is made very versatile.

It is preferred, by what has been said, that the extractor comprises means for detecting the gas pressure of the solvent in the heatable chamber, which can be a pressure gauge readable by the user or an electronic sensor. The accuracy of intervention and automation of the system is improved. The extractor can comprise means for detecting a maximum level of condensate in the extraction chamber, eg. an electronic level sensor, working by inductive or capacitive effect, or an interruptible beam or IR light, or by a float. The level of condensate can then be a parameter in function of which to control the opening of the vent or the open/ closed status of the means for controlling, and thus ultimately the end of an extraction cycle. The means for detecting can comprise an element, movable with respect to the extraction chamber, adapted to define the maximum level of condensate. Such member can be a level-monitoring slider, an emitting photocell or a float.

To optimally automate the extractor, it can comprise an electronic controller, e.g. a PLC, a microprocessor o an electronic discrete- component board, adapted to control the opening of the venting means by piloting the means for controlling. The user thus must not intervene manually anymore. In particular, the electronic controller can make the vent or the valve open when the means for detecting detect that the maximum level is reached, thereby allowing to set experimentally the level that gives the best extraction efficiency and/ or the shortest cycle time with desired performances.

The said two chambers preferably

- are arranged vertically one on the other, to exploit the natural greater mobility of the gas to raise along a vertical, or placed side by side;

- are each accomplished by a container, e.g. one to be used in a laboratory. Advantageously the extractor can be made modular and easily openable to access the matrix or to load solvent by constructing it so that a container (of the two) is partially and sealingly inserted into the other. The part of container being inserted inside the other preferably integrates on a portion of its the septum, thereby forming in simple manner the fluid coupling between the chambers.

It is good that the connection between the containers be both liquid- and gas-tight, e.g. by gaskets, O-rings, sealants or adhesives. Another option is that the containers are threaded and counter-threaded for being able to be screwed one into the other.

In the extractor, solvent vapor can condense directly in the extraction chamber, if it is designed in an appropriate manner. To expedite the condensation and shorten the extraction cycles, the extractor preferably comprises a third chamber, which is

- a refrigerant gravity-fall chamber, and communicating with the extraction chamber;

- preferable arranged vertically on top of the extraction chamber. In the third chamber the solvent vapor is condensed by cooling. The third chamber is very useful when working with low-boiling solvents, when therefore, without coolant, one would lose too much solvent. The third chamber can be integrated into the extraction chamber, thereby making the loading/unloading operations of the sample less easy, though.

The refrigerant chamber can advantageously have modifiable configuration so that in selective manner the solvent's vapor can be trapped or released in it. Preferably said configuration is modifiable so as to create a basin in which condensed vapor is retained and/ or diverted into an external or internal basin. Such configuration variation, e.g in shape or geometry, can be obtained through movable parts of the refrigerant chamber.

A simple variant of movable part is made e.g. by a member or septum or movable wall, for constructive simplicity e.g. movable coaxially and internally in the refrigerant chamber, whose displacement is adapted to modify the shape of the condensation chamber as seen by the solvent's vapor.

The member or septum or movable wall e.g. can be adapted to be moved between two positions: a first position in which, in the refrigerant or condensation chamber, the inlet of the vapor and the outlet of the condensate are both open (and e.g. coincident too) thereby allowing the escape of the condensate, and a second position in which the inlet is open but the outlet is closed, so that the condensate remains in the refrigerant chamber.

Preferably the movable member is a duct having an inlet and an outlet for the vapor.

It is to be noted that the third chamber can be used, with the aforementioned advantages, even as a stand-alone element.

A method is proposed having all the advantages already described for the device. It is an extraction method of non-volatile organic compounds from a solid matrix, comprising the steps of

putting a solvent to heat in a heatabler chamber;

laying a solid matrix in an extraction chamber,

the two chambers being communicating by a septum permeable to vapor of the solvent,

venting the heatable chamber, and

lowering, during use, the gaseous pressure of the solvent.

Other steps of the method are derivable from what has been described for the extractor device.

The advantages of the extractor and the method will be made still clearer by the following description of a preferred embodiment, reference having to the attached drawing in which

- Fig 1 shows a schematic view in vertical section of a well-known extractor,

- Fig 2 shows a schematic view in vertical section of the extractor proposed here;

- Figure 3 shows a transparency section of a refrigerant chamber in a first operating configuration,

- Fig 4 shows a transparency section of the refrigerant chamber in a second operating configuration.

The extractor 50 comprises two containers or receptacles 60, 70, eg. cylindrical and made of glass or metal. The container 60 forms a lower heatable chamber and contains a solvent 62, while the container 70 constitutes an intermediate chamber containing a solid matrix 72 (the sample, eg. placed inside a cellulose extraction thimble).

The containers 60, 70 are preferably configured in such a way that they can be joined firmly and gas-tightly: e.g. the first 60 is inserted into the second 70 and they remain fixed to each other by a plug or hermetic seal 68.

The bottom of the upper container 70 comprises a controlled- porosity septum 80.

The chamber 70 communicates on the upper part with an upper condensation chamber 82 containing a condensing coil 84.

The bottom of the chamber 60 is in contact with heating means 64 for heating the solvent 62.

Between the two receptacles 60, 70 there is a second way of fluid communication comprising an outer tube 98, connected to respective (optional) spouts 66, 72 of the receptacles 60, 70 and equipped with a normally-closed valve 96 that controls and regulates the flow of fluid in the tube 98.

A level sensor or probe 94. positioned eg. inside or within proximity of the chamber 70, serves to control the level of liquid in the chamber 70. When the liquid reaches such a level the probe 94 generates a signal.

The probe 94, the valve 96 and the heating means 64 are controlled and driven by a logic unit 90 (e.g. a PLC, a computer, a microprocessor or an electronic board) interfaced with them through connections 92).

OPERATION

An appropriate amount of extracting solution (solvent 62), or a liquid particularly suitable to dissolve the compound or class of compounds that may be present in the material to be treated (the matrix 72), is inserted into the chamber 60. The material is placed to be treated In the extraction chamber 70, contained in a porous container (extraction thimble 73).

The two receptacles 60, 70 are joined and fixed together, e.g. by any known pneumo-mechanical sealing system. Then the two receptacles 60, 70 are connected to the outer tube 98, by known sealing systems. The chamber 82 is positioned on the extraction gravity-fall chamber 70.

The chamber 60 is positioned on the heating means 64, preferably equipped with electronic temperature control (eg. ± 1 °C), independent from or e.g. executed by the unit 90.

The heating of the chamber 60 causes an increase in pressure due to the vapor pressure, the vapors pass through the porous septum 80 in the extraction chamber 70 where they condense.

As the chamber 60 reaches the temperature set (always greater than the boiling point of the solvent 62) the overheated vapors pass into the extraction chamber 70 where they cause the boiling of the solvent 76 already condensed. The vapors that develop in the extraction chamber 70 condense in the chamber 82 and fall within the same chamber 70. In this way the extraction of the compounds is obtained, and such extraction is particularly effective because it occurs at the boiling temperature of the solvent 62.

When the solvent 76 reaches, in the extraction chamber 70, the level set by the user via the sensor 94, the valve 96, which before was closing the connection through the outer tube 98, is opened, and remains open for a programmable time (eg. using the unit 90).

The opening of the valve 96 causes the immediate drop in the chamber 60 of the present pressure, due both to the resistance offered by the porous septum 80 and the column of condensed solvent and extracted compounds 76 in the extraction chamber 70. The pressure difference existing between the chambers 60, 70 is thus balanced.

The solution 76 present in the extraction chamber 70 then percolates by gravity through the porous septum 80 and returns to the chamber 60.

The valve 96 is closed again and a new extraction cycle can start over.

The advantages of the system are manifold:

- it allows complete extraction of non-volatile compounds from solid matrices thanks to the repeated contact with a boiling solvent. Compared e.g. to the Soxhlet model, there is therefore an improvement in that the extraction takes place with the hot solvent rather than cold one, greatly increasing the effectiveness of each cycle and drastically reducing the time required for completion of the extraction process;

- as an extraction cycle is finished, the solution 76 goes back in the chamber 60 where the solvent evaporates and then condenses, pure, in the extraction chamber 70;

- at each extraction cycle, the solvent 62 in gaseous phase coming out of the chamber 60 through the pipe 98 is all recovered and returned to the chamber 70 after a further washing of the matrix 72.

Figures 3 and 4 show a variant 100 for the cooling or condensation chamber, which can also constitute a stand-alone component. It comprises an elongated outer casing 102 having an input 1 10 and an output 108 for cooling water. The water flows inside a coil 106 placed inside the inner cavity of the casing 102. Coaxially to the cavity, surrounded by the coil 106, extends a tube 120 plugged at one end by a cap 122 and open at the other end 150, which remains internal to the casing 102. The tube 120 is axially movable inside the cavity, so that its open end 150 can abut watertightly (fig. 4) or not (fig. 3) against an opening 104 of the casing 102. The tube 120 has an intermediate hole 130. The chamber 100 is to be coupled eg. with the chamber 70 described before (see fig. 3), forming the top thereof.

OPERATION

During the extraction cycles the tube 120 is raised from the opening

104 (fig. 3). The vapor of solvent coming from the extraction chamber 102 enters the casing 102 (arrows U) and is cooled in contact with the coil 106. Condensed, it goes back down as rain in the extraction chamber (arrows D). At the end of the cycle or when the solvent is to be recovered, the tube 120 is lowered (see arrow F) inside the casing 102 (Fig. 4), so that the end 150 occupies the opening 104. Now, the incoming gas (arrow U) enter into the tube 120, go out of the hole 130 and as before condense. This time, however, the condensed vapor while falling finds the outlet from the casing 102 occluded, and accumulates on the bottom (see basin of liquid condensate 170). From here it can be transported with the casing 102 and/or evacuated by lifting the tube