Improvements in gas chromatography

Abstract

There is provided a preconcentrator unit for gas chromatography. The device comprises an analyte separation portion, a temperature sensor arranged to provide measurements to a closed-loop controller and a heating element and a cooling element, wherein the heating element and the cooling element are arranged to be controlled by the closed-loop controller, and wherein the closed-loop controller is arranged to operate the heating and cooling elements to cause the analyte separation portion to undergo a temperature profile, wherein the temperature profile comprises a series of successive high temperature peaks separated by intervening lower temperature periods, each successive high temperature peak is higher than the previous high temperature peak and each intervening low temperature period is at a higher temperature than the previous intervening low temperature period.

Description

[0001] IMPROVEMENTS IN GAS CHROMATOGRAPHY

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to gas chromatography, in particular micro-gas chromatography (micro-GC).

[0004] BACKGROUND

[0005] A gas chromatography instruments are used for detecting and determining a concentration of gas or volatile compounds, particularly a mixture. In general terms, such an instrument has a chromatographic column which has the ability to separate a mixture of gasses into individual components, and a detector that outputs a signal depending on the concentration and / or type of compounds that passes through the column.

[0006] Reducing the size of gas chromatography instruments is desirable. Indeed, it is desired to make instruments of the size of silicon chips - these are often called ‘micro gas chromatographs’ or micro-GC, for short.

[0007] SUMMARY OF THE INVENTION

[0008] To these ends, there is provided a device, a system and methods according to the appended claims.

[0009] In particular, there is provided a device for gas analysis. The device comprises an analyte separation portion, a temperature sensor arranged to provide measurements to a closed-loop controller, a heating element and a cooling element. The heating element and the cooling element are arranged to be controlled by the closed-loop controller, and the closed-loop controller is arranged to operate the heating and cooling elements to cause the analyte separation portion to undergo a temperature profile. The temperature profile comprises a series of successive high temperature peaks separated by intervening lower temperature periods, each successive high temperature peak is higher than the previous high temperature peak and each intervening low temperature period is at a higher temperature than the previous intervening low temperature period.

[0010] The temperature of each peak is set to trigger desorption of a particular analyte and the following cool period serves to flush residuals of analyte along the column before the next desorption is triggered. The increasing peak temperatures trigger desorptions in series according to the molecular weight and degree of binding of the analyte to the solid phase and the intervening cool phases are also chosen to provide the flushing for the analyte in question. In an aspect, the device comprises a second device of a similar type, the second device having an analyte separation portion and a temperature sensor arrange to provide measurement to the closed-loop controller.

[0011] In an aspect, the device has the coupling arranged to allow it to be connected to a gas chromatography instrument.

[0012] In an aspect, the device of claim comprises the closed-loop controller. This allows a tight integration and size-reduction. The size-reduction is, in itself, useful since it aids reducing thermal mass for the overall system.

[0013] In an aspect, where there are two devices, the closed-loop controller is arranged to apply a second series of high temperature peaks to the second device, the second series of high temperature peaks being synchronized with the high temperature peaks of the first.

[0014] In an aspect, the closed-loop controller is arranged to interrupt a flow of a gas to the device, the interruptions being synchronized with the high temperature peaks applied the device. More particularly, there is an interruption during the ramp-up and ramp-down of the temperature with reestablishment of the flow of the gas during the actual peak. This allows reduction of the effective thermal mass of the device and so allows for more precise temperature ramps. Reestablishing the flow of the gas during the peak i.e. the plateau or high / target temperature part of the peak, allows the desorbed analyte to be swept down the column.

[0015] There is provided, a method of operating a device for gas chromatography, the device having an analyte separation portion, the method comprising applying a temperature profile, the temperature profile comprising a series of successive high temperature peaks separated by intervening lower temperature periods, each successive high temperature peak is higher than the previous high temperature peak and each intervening low temperature period is at a higher temperature than the previous intervening low temperature period.

[0016] In an aspect, the method comprises applying a series of interruptions to a flow of a gas to the analyte separation portion, wherein the interruptions are synchronized with the application of the high temperature peaks. More particularly, there is an interruption during the ramp-up and ramp-down of the temperature, with reestablishing of the flow of the gas during the actual peak.

[0017] In an aspect, in a two-device embodiment, a temperature profile of high temperature peaks is applied to the second device and the high temperature peaks are synchronized with the peaks applied to the first device.

[0018] In an aspect, when applied to a gas chromatography instrument comprising a chromatography column, the method comprises applying a series of temperature ramps and plateaus to the column, wherein the temperature ramps are synchronized with the high temperature peaks applied to the device. There is provided gas chromatography instrument comprising a device according to any of claims 1 - 6, a chromatography column, a detector, and when the closed-loop controller of claim 4 is not present, a closed-loop controller.

[0019] In an aspect, the closed loop controller is arranged to apply a second series of temperature ramps and plateaus to the chromatography column, wherein the temperature ramps are synchronized with the high temperature peaks applied to the device.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above, as well as additional objects, features and advantages of the disclosed devices, systems and methods, will be better understood through the following illustrative and non-limiting detailed description of embodiments of devices and methods, with reference to the appended drawings, in which:

[0022] Fig. 1 represents chromatograms illustrating phenomena relevant to the present invention.

[0023] Figs. 2a - 2c represent, in schematic form, variations on agas chromatography instruments, each according to an embodiment.

[0024] Figs. 3a - 3d represents a first stage of the gas chromatography of Fig. 1, according to an embodiment.

[0025] Fig. 4 represents a simplified cross-section view of the instrument of Fig. 1.

[0026] Fig. 5 represents a temperature profile applied to the first stage of the first stage represented in Fig. 2

[0027] Fig. 6 represents a chromatogram in an experiment using a device according to an embodiment.

[0028] Fig. 7 represents a temperature profile applied to a gas chromatography instrument.

[0029] Fig. 8 illustrates a phenomenon related to heating and thermal mass.

[0030] Fig. 9 represents a heating profile and gas flow control.

[0031] Fig. 10 represents heating profiles applied to a device according to Fig. 2b.

[0032] DETAILED DESCRIPTION OF EMBODIMENTS

[0033] In the following description, same references designate like elements. Elements that have been described will not be described further.

[0034] In gas chromatography, a mixture of volatile compounds (analytes) is allowed to be absorbed on a sorbent (also known as the solid phase) arranged along a tube, or ‘column’. The attraction or bonding is by weak electrostatic forces such as van der Waals or hydrogen bonds, and, as such can be broken by thermal excitation. The increased thermal ambient increases the kinetic energy of the molecules to the extent that they detach (or ‘desorb’ or ‘elute’) from solid phase and are picked up by a gas flowing through the column (the fluid phase) and carried along the column. Since different molecules will have different degrees of attachment to the solid and different molecular weights, they will be absorbed at different places - those analytes which have weaker attractions and / or lower molecular weights will be absorbed further down the column. The analytes will also require differing amounts of kinetic energy to desorb - in other words, they can be made to desorb separately. This provides an opportunity to separate the different molecules in that different compounds entering the column at a same time may be caused to leave the column at different times. This in turn allows identification of those compounds and, ideally, their concentrations in the original mixture. It should be understood that there is a stochastic aspect to the processes of absorption and desorption.

[0035] The length of column imposes a limit on the number of analyte compounds it can separate. Typically, this scales with the square root of the length of the column. This fact has an important outcome for the shorter length columns, which are beneficial for so-called process gas chromatographs, and even more so for micro gas chromatographs, in that the recorded chromatogram may not present isolated peaks, but rather a superposition of partially or fully overlapping peaks. This means that it may become difficult to identify the actual peak corresponding to the compound(s) (also referred to as ‘markers’) of interest. Further, it may be difficult to determine the peak area of the marker of interest - in part because the area needs to be corrected for the overlapping contributions of the neighboring peaks. This results in inaccuracies and even errors in the determination of the marker concentration.

[0036] Fig. 1 shows the result of an experiment with GC instrument by of illustration of this effect. In this experiment, a series of paraffins having carbon chains of C5 to C8 has been released into a column similar to n embodiment and allowed to absorb onto the solid phase. On the left-hand side, trace T1 represents a temperature profileover time with single Direc-like heating pulse of 160°C and trace T2 represents thedesorption of the analytes iseen at the detector. On the right-hand side, trace T3 represents a temperature-time profile with a short pulse to 95°C followed by a dwell at 90°C and trace T4 represents resultant peaks of the analytes seen by the detector at the end of the column. As can be seen, the peaks of the analytes are considerably broadened in the second case and, in the case of C5 and C6, partially overlapping, despite the attempt to achieve very narrow desorption pusles. Thus is it clear that accurate concentrations determination, even in this simplified example, is rendered more difficult.

[0037] The inventors were thus led to make a number of realizations. A simple Dirac-like heating pulse and heating to just 90°C (to favour the more mobile analytes) was both insufficient though very short pulses (the first case above) seemed more promising. They then realized that a series of pulses in a ramp of pulses could be used to obtain greater selectivity in the desorption. Current approaches use temperature peaks which trigger unselective desorption and rely on the column properties for separation. They then realized that the current open-loop control systems are insufficient for the precise series of peaks. They then discovered that the present cooling method i.e. using the gas flow in open loop presents problems in that it is hard to control the ramp-downs and cool periods. Thus, they found that a closed- loop temperature control presents advantages. It should be noted that, opting for active control over the cooling is counterintuitive in that it introduces complexity and replaces a logical choice, namely cooling by something that it already there - the gas. The situation may be improved by the use of a preconcentrator unit (PCU) to achieve a degree of separation of the analytes before introducing the mixture to the column. This, among other things, reduces the numbers and amounts of analytes travelling simultaneously down the column.

[0038] Fig. 2a shows a version of an exemplary gas chromatography instrument 1 according to an embodiment. A valve 2 allow entry of a gas flow and material to be analysed into the instrument. A pressure regulator 3 is coupled to the valve 3 for the purpose of controlling the pressure of the flow that enters a PCU 4, which is coupled to output of the pressure regulator 3 (or valve 2 if the pressure regulator is not used. The output of the PCU 4 is coupled to one input of a combiner 5. From the valve 2 a secondary output is coupled to a flow reducer 6 which is in turn coupled to a second input of the combiner 5. The output of the combiner is coupled to a chromatography column 7 (forthwith ‘column’). The output of the chromatography column 7 is coupled to a detector 8. From the detector, there is a coupling to an output or exhaust 9. The valve 2, pressure regulator 3 and the bypass path formed by the flow reducer 6 and combiner 5 are optional.

[0039] Fig. 2b shows a variant where a second PCU 10 is coupled between the first PCU 4 and the chromatography column 7. A second PCU may be useful to improve the separation / preconcentration, particularly in the presence of analytes that tend to desorb together. In summary, in this variant, the device comprises a second device of a similar type, the second device having and analyte separation portion and a temperature sensor arrange to provide measurement to the closed-loop controller. The advantages of this variant are discussed in connection with Fig. 10.

[0040] Fig. 2c shows another variant where a coupling 11 is present between the PCU 4 and the column 7. In a variant, the coupling allows for an input 12 and an output 13. Such a variant may be of use where the PCU 4 and column 7 are provided separately and integrated.

[0041] The detector 8 may be implemented is various ways. There are different types of detectors, such as photo ionization, flame ionization, chemoresistive and amperometric, thermal conductivity and mass spectrometry. Other types may be possible.

[0042] Fig. 3a shows a plan view of a first side of a PCU 4 for a micro-GC according to an embodiment. Inlet / outlets 21 connect with a channel 22 provided in the substrate 23 of the PCU 4. This is shown in 3-D in Fig. 3b. The column 7 may have a similar construction. A possible method of construction of the PCU may involve use of etching techniques (such as Deep Reactive Ion Etching or ‘DRIE’) on silicon in order to form the inlet / outlets and the channel 22. The column 7 may be formed in a similar manner thought it will typically have a much longer channel than that of the PCU.

[0043] Fig. 3c shows a plan view of the other side of the PCU 4. Contacts 24, 25 provide coupling to a heater element 26 arranged in a serpentine trace over the surface of the PCU 4. A second set of contact 27, 28 provide coupling to a temperature sensor 29.

[0044] Fig. 3d represents a variant, where a Peltier junction 27 is arranged in an interdigitated fashion between the windings of serpentine trace of the heater element 26. It should be noted that, in a variant, the Peltier junction, is replaces by a path allowing the flow of a coolant, the flow being arranged to be controllable.

[0045] Fig. 4 represents a cross-sectional view of a gas chromatography instrument according to an embodiment. A PCU 4 and a column 7 are arranged on an intermediate layer (or interposer) 32, which is in turn arranged on a support layer 32. The channel 22 as shown in Figs. 2a and 2b forms a closed volume 34 with the interposer 31 through which the gases may flow. The same applies for the column 7 which possesses an analogous channel (not shown). It should be understood that the closed volume 34 of the PCU 4 may also be considered as a column in the sense of a term of chromatography. The interposer 31 and the support layer 32 are arranged to provide a channel 33 for gas flow. The gas flow may enter the channel 33 via an inlet 35. In the interposer 31 are arranged passages 36 - 38 which connect the channel 33 to the enclosed volumes of the PCU and the column. A detector 8 is arranged on the interposer 31 so as to receive glass flow from the channel 33. Finally the channel 33 arrives at an outlet 9. The closed volumes 34 of the channels 22 in the PCU 4 and column 7 are filled with a sorbent. Possible choices for the sorbent are highly porous polymers such as Tenax TA or Carbotrap for the PCU 4 and PDMS for the column 7. Fig. 4 is not drawn to scale and nothing may inferred from it about relative sizes of the various parts. Indeed, the column 7 may be much larger and longer than the PCU 4.

[0046] In a variant, not shown, the closed-loop controller, is mounted on the instrument. In a further variant, it is integrated into the PCU 4. The advantages of having the closed-loop controller closely integrated are that the complexity of the connections is reduced (and made more reliable) which in turn means that the final instrument may be more compact. In the case where the PCU 4 is manufactured in silicon such as in Figs. 3a - d, it may be convenient to manufacture the PCU 4 as a microcontroller or some programmable logic technology. It may be possible to make the controller in dedicated logic. However, programmability would allow different temperature profiles to be included later,

[0047] Typically. GC operation involves a raising of the column temperature to trigger desorption and then, sometimes a rapid cooling to a cool phase - usually where the column is flushed of analytes. It is possible to use multiple heating peaks but the inventors have observed that the problems of analyte peak broadening and overlap still persist. The inventors have discovered that the heating pulses and the cool periods may individually tailored to trigger the desorption of individual analytes in the PCU and to ensure an improved degree of separation between then when they are transported into the column.

[0048] Fig. 5 represents an idealized version of heating profile according to an embodiment as applied to a PCU 4. In it, a series of short heating pulses 51 are applied to the PCU 4. Between each heating pulse, the PCU 4 is cooled and held, for an intervening cool period 52 at a temperature below that of the heating pulse. The temperature of the intervening cool period 52 is chosen in order to flush out residual analytes of the type just released by the pulse so as to avoid them being released during the next heating pulse and ‘polluting’ that subsequent peak. Each successive heating pulse 51 is to a higher temperature than the previous and each intervening cool period is at a higher temperature than the previous intervening cool period 52. The earlier heating pulses will trigger desorption of the lighter / least well attached analytes but, being at too low a temperature for the heavier / better attached, not trigger (significant) desorption of these. In other words, the temperature of each heating pulse is chosen to trigger desorption of a single analyte. Furthermore, at a given temperature, heavier analytes will travel more slowly along a column than lighter ones. Conversely, higher temperatures permit a given analyte to progress faster. Therefore, the higher temperatures used for the later pulses also have the effect of helping the later-released, heavier analytes move faster down the column. This has the benefit of allowing the overall cycle to be shorter.

[0049] In summary, there is a device for gas analysis. The device comprises an analyte separation portion, a temperature sensor arranged to provide measurements to a closed-loop controller, a heating element and a cooling element. The heating element and the cooling element are arranged to be controlled by the closed-loop controller, and the closed-loop controller is arranged to operate the heating and cooling elements to cause the analyte separation portion to undergo a temperature profile. The temperature profile comprises a series of successive high temperature peaks separated by intervening lower temperature periods, each successive high temperature peak is higher than the previous high temperature peak and each intervening low temperature period is at a higher temperature than the previous intervening low temperature period. The temperature of each peak is set to trigger desorption of a particular analyte and the following cool period serves to flush residuals of analyte along the column before the next desorption is triggered. The increasing peak temperatures trigger desorptions in series according to the molecular weight and degree of binding of the analyte to the solid phase and the intervening cool phases are also chosen to provide the flushing for the analyte in question.

[0050] Better separation is achievable when the exact parameters of the profile are adapted to the particular analyte mix. When the instrument is intended for use within a specific setting such as medical examination of exhaled air or gas leak detection, it may be possible to define a series of ‘standard’ profiles that the user may select between, since the range of analytes may be relatively well defined and known in advance.

[0051] Fig. 6 shows the results of practical examples of a controlled desorption using a profile like that of Fig. 5. Trace t61 shows the applied thermal profile overtime and trace t62 shows the resulting peaks of the analytes exiting the PCU 4 over time. For the first heating pulse, the PCU 4 is heated from 30°C to 100°C and then cooled for a 7-minute period at 40°C. The second heating pulse is then 120°C. Initially, at point 63, C5 and C6 desorb close together and there is partial overlap in their peaks. At this point, C7 is barely observable. At point 64 and later, peaks of C7, C8 and C9 emerge, displaying clear separation, demonstrating the effectiveness the technique of staggered desorption and flushing.

[0052] Fig. 7 shows temperature profiles, 71, and 72, applied to respectively the PCU4 and the column 7. As mentioned previously, a higher temperature allows a heavier analyte to progress faster along the column. This has the advantage of allowing the cycle to be shortened.

[0053] Fig. 8 represents an exemplary temperature ramp by way of illustration of a relevant phenomenon. The solid trace represents the applied power to the heating element and the dotted trace represents, in an exaggerated form, the actual temperature change seen by the heated / cooled object - in this case the PCU or column. As can be seen, the actual ramp is delayed both in starting and even more so in arriving at the target temperature and there is a degree of overshoot. This arises because the material of the PCF channel (i.e. column) has a thermal mass and finite thermal conductivity. The same will be true for the cooling ramp.

[0054] Fig. 9 represents athermal profile, according to a variant, applied to a PCU with synchronized interruption of the flow of the fluid phase. During the ramp-up and ramp-down of heating pulses, the fluid phase flow is cut and then reestablished during the actual peak plateau - such as at 91. Since the fluid phase is usually fed in at a constant temperature (usually around ambient), it has the effect of increasing the effective thermal inertia of the PCU, exacerbating the effects described in relation to Fig. 8. Therefore, cutting the gas flow may reduce lag to hitting target temperature and peak broadening. Reestablishing the gas flow during the peak period (i.e. the plateau or high / target temperature part of the peak) allows the desorbed analyte to be driven down the channel.

[0055] Fig. 10 represents thermal profdes used with the instrument as shown in Fig. 2b. The first trace tlOl represents the profile applied to the first PCU 4 and the second trace, 1102, represents the thermal profile applied to the second PCU 10. The main advantage is that the first PCU 4 can be large to in order to be able store a large number of different compounds. Being large, it has, therefore a higher thermal capacity, The second PCU 10, is, in this case, is smaller so that it has a lower thermal capacity. The lower thermal capacity allows faster temperature ramp ups and -ramp-downs. This allows for more precise desorption triggering.

[0056] It is highly advantageous to have accurate control of the thermal profile that the column of the PCF actually sees since it is desired to have a well-separated series of temperature pulses. The phenomenon described here will have the effect of broadening the pulses and reducing the separation efficiency. Many GC instruments rely on open-loop control of the temperature. As can be understood from the foregoing, significant overshoot may be highly undesirable in that some desorption of ‘the wrong analyte’ (i.e. an analyte which would preferably left until later to desorb) may be triggered. Overshoot on the cooling cycle may have the effect of reducing the flushing time which in turn may leave residual analyte to trickle out and affect the results for later analytes.

[0057] However, the thermal sensor 29, described in relation to Fig. 2c allows closed-loop control which is inherently more precise. If a proportional, integral and differential (PID) controller is used, this allows control of the applied power in real-time which helps achieve reduction of the lag and overshoot, both on heating and cooling, allowing the devices to approach their desired temperature profiles. Many GC instruments rely on cooling provided by the fluid phase i.e. cool gas is introduced. This is convenient since it is by definition available. However, this allows for less control than direct cooling such as with the variant of Fig. 3d. Direct cooling, using something like fluid flow or a Peltier junction would allow even better control since both heating and cooling could be applied simultaneously. It may be possible to combine such a variant with that of Fig. 9 in that the controller also has control over the gas flow.

[0058] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0059] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer or processing unit. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0060] Aspects of the invention may be implemented in a computer program product, which may be a collection of computer program instructions stored on a computer readable storage device which may be executed by a computer. The instructions of the present invention may be in any interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs) or Java classes. The instructions can be provided as complete executable programs, partial executable programs, as modifications to existing programs (e.g. updates) or extensions for existing programs (e.g. plugins). Moreover, parts of the processing of the present invention may be distributed over multiple computers or processors.

[0061] Storage media suitable for storing computer program instructions include all forms of nonvolatile memory, including but not limited to EPROM, EEPROM and flash memory devices, magnetic disks such as the internal and external hard disk drives, removable disks and CD-ROM disks. The computer program product may be distributed on such a storage medium, or may be offered for download through HTTP, FTP, email or through a server connected to a network such as the Internet.

Claims

CLAIMS:

1. A device for chromatography, the device comprising an analyte separation portion; a temperature sensor arranged to provide measurements to a closed-loop controller a heating element and a cooling element, wherein the heating element and the cooling element are arranged to be controlled by the closed-loop controller, and wherein the closed-loop controller is arranged to operate the heating and cooling elements to cause the analyte separation portion to undergo a temperature profde, wherein the temperature profile comprises a series of successive high temperature peaks separated by intervening lower temperature periods, each successive high temperature peak is higher than the previous high temperature peak and each intervening low temperature period is at a higher temperature than the previous intervening low temperature period.

2. The device of claim 1 comprising a second device, the second device having an analyte separation portion and a temperature sensor arranged to provide measurement to the closed-loop controller.

3. The device of claim 1 comprising a coupling arranged to allow it to be connected to a gas chromatography instrument.

4. The device of any preceding claim comprising the closed-loop controller.

5. The device of claim 4, when dependent on claim 2, wherein the closed-loop controller is arranged to apply a second series of high temperature peaks to the second device, the second series of high temperature peaks being synchronized with the high temperature peaks of the first.

6. The device of either claims 4 or 5 wherein the closed-loop controller is arranged to interrupt a flow of a gas to the device, wherein the interruptions are synchronized with the high temperature peaks applied the device.

7. A method of operating a device for gas chromatography, the device having an analyte separation portion, the method comprising applying a temperature profile, the temperature profile comprising a series of successive high temperature peaks separated by intervening lower temperatureperiods, each successive high temperature peak is higher than the previous high temperature peak and each intervening low temperature period is at a higher temperature than the previous intervening low temperature period.

8. The method of claim 7 comprising applying a series of interruptions to a flow of a gas to the analyte separation portion, wherein the interruptions are synchronized with the application of the high temperature peaks.

9. The method of claims 7 or 8 wherein a temperature profde of high temperature peaks is applied to a second device and wherein the high temperature peaks are synchronized with the peaks applied to the first device.

10. The method of any of claims 7 - 9, when applied to a gas chromatography instrument comprising a chromatography column, comprising applying a series of temperature ramps and plateaus to the column, wherein the temperature ramps are synchronized with the high temperature peaks applied to the device.

11. A gas chromatography instrument comprising a device according to any of claims 1 - 6, a chromatography column, a detector, and when the closed-loop controller of claim 4 is not present, a closed-loop controller.

12. The gas chromatography instrument of claim 11 wherein the closed loop controller is arranged to apply a second series of temperature ramps and plateaus to the chromatography column, wherein the temperature ramps are synchronized with the high temperature peaks applied to the device.

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