Process for thermally desorbing a phase material

Abstract

In a process for thermally desorbing a phase material (20), in particular for conditioning a fiber for carrying out a solid-phase microextraction, the phase material (20) is heated along a temperature curve. The temperature curve of the phase material (20) during desorption includes at least one low point.

Claims

1. A process for thermally desorbing a phase material, wherein the phase material is heated along a temperature curve, characterized in that the temperature curve of the phase material during desorption includes at least one low point.

2. The process as claimed in claim 1, wherein a temperature difference between a maximum temperature of the temperature curve and the low point of the temperature curve is between 50° C. and 500° C.

3. The process as claimed in claim 2, wherein the maximum temperature is between 100° C. and 600° C.

4. The process as claimed in claim 2, wherein the low point is between 0° C. and 300° C.

5. The process as claimed in claim 1, wherein the temperature curve includes more than one low point.

6. The process as claimed in claim 3, wherein, between two low points, a high point is in each case reached that is greater than 0.8 times.

7. The process as claimed in claim 1, wherein a time interval between 15 and 600 seconds, preferably between 30 and 300 seconds, particularly preferably between 60 and 240 seconds is between two low points at neighboring times.

8. The process as claimed in claim 1, for conditioning a fiber for carrying out a solid-phase microextraction.

9. The process as claimed in claim 2, wherein a temperature difference between a maximum temperature of the temperature curve and the low point of the temperature curve is between 100° C. and 400° C.

10. The process as claimed in claim 9, wherein a temperature difference between a maximum temperature of the temperature curve and the low point of the temperature curve is between 150° C. and 350° C.

11. The process as claimed in claim 3, wherein the maximum temperature is between 150° C. and 400° C.

12. The process as claimed in claim 11, wherein the maximum temperature is between 200° C. and 300° C.

13. The process as claimed in claim 4, wherein the low point is between 10° C. and 150° C.

14. The process as claimed in claim 13, wherein the low point is between 15° C. and 50° C.

15. The process as claimed in claim 5, wherein the temperature curve includes between 2 and 10 low points.

16. The process as claimed in claim 15, wherein the temperature curve includes between 4 and 8 low points.

17. The process as claimed in claim 6, wherein, between two low points, a high point is in each case reached that is greater than 0.9 times the maximum temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings which are used to explain the working example:

(2) FIG. 1 shows a first embodiment of a temperature curve for the conditioning process;

(3) FIG. 2 shows a second embodiment of a temperature curve for the conditioning process;

(4) FIG. 3 shows a third embodiment of a temperature curve for the conditioning process;

(5) FIG. 4 shows a fourth embodiment of a temperature curve for the conditioning process;

(6) FIG. 5 shows a fourth embodiment of a temperature curve for the conditioning process; and

(7) FIG. 6 shows a schematic representation of a device for carrying out conditioning of a fiber for SPME.

(8) In principle, identical parts are provided with the same reference signs in the figures.

WAYS OF IMPLEMENTING THE INVENTION

(9) FIGS. 1 to 5 below show various embodiments of a temperature curve. The temperature curves here reflect the temperature of the phase material. The temperature rises in particular are each dependent on a heat output of the chamber and the layer thickness of the phase material, which means that the slope in these regions may be significantly greater, but may also be smaller. Similarly, the slopes in the cooling phases may be greater or smaller, depending on the type of cooling and the layer thickness of the phase material. The temperature curves are intended in particular to also allow a qualitative view of the process, whereas the minimum and maximum temperatures and also the slopes of the temperature curves and the hold times of the temperatures in the temperature curves should not be restricted to the examples.

(10) FIG. 1 shows a first embodiment of a temperature curve for the conditioning process of a phase material in a chamber. The chamber is heated with the heating unit to a constant 300° C. The temperature of the chamber remains constant throughout the conditioning process. At time 0, the fiber is exposed in the chamber and thus heated for 60 seconds. The fiber is then removed from the chamber and allowed to cool in the ambient air. The end temperature after the cooling process is approximately room temperature, in the present case about 25° C. The cooling process lasts 60 seconds. The fiber is then exposed again in the chamber at the temperature of 300° C. for 60 seconds, through which the temperature of the fiber increases from room temperature to 300° C. and is maintained at 300° C. These steps are repeated until the temperature of 300° C. has been reached six times. The process ends after the last cooling process.

(11) In this first embodiment, the temperature curve has five local minima/five low points at a temperature of approximately 25° C. The maximum temperature and the local maxima are each at a temperature of 300° C. The total cycle takes around 12 minutes therewith.

(12) FIG. 2 shows a second embodiment of a temperature curve for the conditioning process of an adsorbent in a chamber. The chamber is heated with the heating unit to a constant 250° C. The fiber is heated for 90 seconds in the chamber, reaching a maximum temperature of 250° C. The heating unit is then switched off for 60 seconds, whereupon the temperature falls from 250° C. to about 50° C. The heating unit is switched on again, whereupon the temperature rises to 250° C. within 30 seconds and is held for 60 seconds. These steps are repeated until the temperature has been held at 250° C. for 60 seconds five times. The process ends after the cooling process, i.e. at about 50° C.

(13) In this first embodiment, the temperature curve has four local minima/four low points at a temperature of 50° C. The maximum temperature and the local maxima are each at a temperature of 250° C. The total cycle takes around 12.5 minutes therewith. In this second embodiment, the selected maximum temperature is lower than in the first embodiment, but is held for longer. In addition, instead of 6 cycles there is provision only for 5 cycles.

(14) Whereas in the second embodiment the chamber is preferably provided with an electric heating element, it may alternatively also be heated by other means that respond less sluggishly, for example it may be heated with hot gas, microwaves or other means of heating known to those skilled in the art. The cooling process may be effected with cooled gas or with a gas at room temperature. These variants may also be provided in the other exemplary embodiments.

(15) FIG. 3 shows a third embodiment of a temperature curve for the conditioning process of an adsorbent in a chamber. The starting temperature in the chamber is about 300° C. and remains constant during the process. The fiber is introduced into the chamber and heated to 300° C. for 60 seconds. The fiber is then removed from the chamber and allowed to cool to 100° C. for a further 60 seconds. These steps are repeated until the temperature of 300° C. has been reached five times. The process ends after the last cooling process at room temperature.

(16) In this third embodiment, the temperature curve has four local minima/four low points at a temperature of 100° C. The maximum temperature and the local maxima are each at a temperature of 300° C. The total cycle takes around 10 minutes therewith. In this third embodiment, the selected minimum temperature is higher than in the first embodiment. The maximum temperature of 300° C. is reached only at individual points and is not held for a longer period. There is provision for 5 cycles in the present process.

(17) FIG. 4 shows a fourth embodiment of a temperature curve for the conditioning process of an adsorbent in a chamber. The starting temperature in the chamber is about 150° C. The fiber is fed into the chamber for 60 seconds. The fiber is then cooled inside a cannula for 60 seconds in the ambient air to a temperature of about 75° C. During this time, the temperature in the chamber is increased by 25° C. to 175° C. After the cooling process, the fiber is subjected to the temperature of 175° C. in the chamber for 60 seconds. During this process, the fiber is exposed, i.e. it is fed out of the cannula. The fiber is then fed back into the cannula and cooled in the ambient air to a temperature of about 100° C., while the chamber is heated to a temperature of 200° C. These steps are repeated until a low point/local minimum has been reached four times. The process finally ends at room temperature after the last cooling process.

(18) In this fourth embodiment, the temperature curve has four local minima/four low points, which increase successively by a temperature of 25° C. The temperature curve thus shows a trend with positive slope. The maximum temperature is reached after 8 minutes and 30 seconds and is 250° C.

(19) It will be clear to those skilled in the art that the temperature curve may be varied as required without departing from the basic concept of the invention. The trend for the temperature curve shown in the fourth embodiment may also have a different profile, for example with negative slope. In addition, the local minima and local maxima may describe their own functions that deviate from a straight line. The minima and maxima may form a zigzag curve. The minima and maxima of a temperature curve do not need to have a parallel profile, etc.

(20) The individual temperature profiles may in each case be achieved by different chamber heating units and by different cooling techniques. Thus, the second exemplary embodiment of a temperature curve may, for example, also be achieved with an additional cooling chamber, etc.

(21) FIG. 5 shows a fifth embodiment of a temperature curve for the conditioning process of an adsorbent in a chamber. The starting temperature in the chamber is about 250° C. and remains constant during the conditioning process. The fiber is fed into the chamber for 30 seconds and heated to a temperature of 250° C. The fiber is then transferred to a separate cooling chamber and cooled to approximately room temperature for 30 seconds. After this, the fiber is returned to the chamber, where it is then subjected to the temperature of 250° C. for 120 seconds. The fiber is then transferred to a separate cooling chamber and cooled to approximately room temperature for 30 seconds. After this, the fiber is returned to the chamber, where it is subjected to the temperature of 250° C. for 30 seconds. These steps are repeated until a low point/local minimum has been reached five times. The process finally ends at room temperature after the last cooling process.

(22) FIG. 6 shows a schematic representation of an embodiment of a chamber 10 having a heating unit 14, in which a fiber 20 comprising the phase material is positioned. The chamber 10 comprises a housing 11 with an inner space 12, in which a heating unit 15 is positioned. The heating unit 14 is cylindrical in the present case, in particular is designed as a heating coil into which the fiber 20 may be introduced. The heating unit may alternatively be of a different design, for example the heating unit may be positioned only on one side in the inner space 12 or at the bottom of the inner space 12. The chamber 10 further comprises a fluid inlet 13 in the bottom region of the housing 11 with which a fluid may be fed into the inner space 12. The fluid is used to flush the inner space 12 during conditioning of the fiber. This can avoid an equilibrium being reached between the desorbed analyte and the fiber in the inner space 12. The fluid may be gaseous or liquid. It is particularly preferably an inert gas, for example nitrogen or a noble gas. In addition to, or as an alternative to, flushing the inner space, the fluid may also be used for cooling the fiber, which allows the low points of the temperature curve to be reached more swiftly. Here too, the fluid may be gaseous or liquid. Finally, in addition to, or as an alternative to, cooling or flushing, the fluid may also be used to heat the fiber, which allows the local maxima of the temperature curve to be reached more swiftly, with the fluid again being gaseous or liquid.

(23) The device for carrying out conditioning may be provided in the form of a separate chamber to be used exclusively for conditioning. Alternatively, a heatable injector of an analyzer, in particular a chromatograph, may be provided as a chamber.

(24) The device may further comprise a separate cooling chamber, with the fiber able to be transferred during the process to the cooling chamber for cooling. The cooling chamber may be actively cooled or merely have an inert gas passed through it at room temperature.

(25) Instead of, or in addition to, the cooling chamber, the device may also comprise a fan. The fan may be positioned outside the chamber so that the fiber, in particular the fiber present in the cannula, is positioned outside the chamber in front of the fan for cooling, allowing the fiber to be cooled by the air flow directly or indirectly. However, with the fan it is also possible for a cooling gas (actively cooled or at room temperature) to be passed through the chamber to cool the fiber. In this case, the fiber would not need to be removed from the chamber for the cooling process. In addition, the fan may also be positioned in a separate cooling chamber, thereby allowing a cooled or uncooled gas, in particular an inert gas, to be passed through the cooling chamber to cool the fiber. Those skilled in the art will be aware of further options for cooling the fiber more efficiently or more simply.

(26) Whereas FIG. 6 shows a device for conditioning a fiber, it will be clear to those skilled in the art that other phase materials may likewise be conditioned with the process according to the invention. For example, the process may also be used for conditioning a phase material for SPE.

(27) In addition, the process may also be used for gentle conditioning of HPLC or GC columns. Those skilled in the art will be aware of further possible applications of the process according to the invention.

(28) In summary, it can be stated that the invention provides a particularly gentle process for carrying out conditioning or preparation of a phase material for chemical analysis, in particular for conditioning a fiber for SPME.