WO2010066773A1

WO2010066773A1 - Improved separating column module for a gas chromatograph

Info

Publication number: WO2010066773A1
Application number: PCT/EP2009/066700
Authority: WO
Inventors: Gerhard Krebs; Felix Scharstein
Original assignee: Gerhard Krebs; Felix Scharstein
Priority date: 2008-12-11
Filing date: 2009-12-09
Publication date: 2010-06-17
Also published as: DE102008054546B3

Abstract

The invention relates to a separating column module for a gas chromatograph, comprising a separating column (24) and an electric heater (12) for the separating column (24), wherein the heater (12) comprises at least one coil (14) and a power source for generating a alternating magnetic field through the coil (14), and also a heating unit (16), wherein the heating unit is disposed adjacent to the separating column (24) and within the alternating magnetic field such that the separating column (24) is heated. The module is characterized in that the heating unit (16) comprises at least one flat radiator element (18) that can be at least partially magnetized and/or is at least partially conductive.

Description

Designation: Improved separation column module for a gas chromatograph

The invention relates to a separation column module for a gas chromatograph, with a separation column and an electric heater for the separation column. Such separation columns are used in gas chromatographs in order to separate mixtures of volatile components introduced into the separation column, so that they can be characterized on the basis of their retention time and quantified by their detection signal. In order to obtain an improved separation effect, the separation column is heated according to a predetermined temperature program, so that the vapor pressures in the mixture to be analyzed change.

Because of their good controllability, heaters based on resistance wires are currently used, in which current is passed through the resistance wire, which then heats up and heats the separation column.

A disadvantage of known separation column modules is their high power consumption. This leads in addition to a high heat load on any air conditioning, with the environment of the gas chromatograph is maintained at a predetermined temperature.

In order to minimize the consumption of electrical energy of the gas chromatograph and the downstream cooling, an attempt is made to reduce the thermal mass of the separation column module. The thermal mass is the amount of material that must be heated during heating. For example, heating wires are laid directly along the capillary acting as a separation column. The disadvantage of this is the high production costs. It is another disadvantage that such systems have a relatively long heating time, that is, that the temperature change per minute is limited upwards.

From WO 94/04915 a gas chromatograph with a separation column designed as a capillary and a heating unit is known in which the separation column or a support receiving the separation column is arranged at a radial distance around the core of a transformer to form a secondary circuit to inductively to be heated by the primary circuit. This embodiment has the disadvantage that the heating is not sufficiently uniform. The invention has for its object to propose a separation column module that generates little waste heat and yet allows rapid and uniform heating and / or cooling.

This object is achieved by a generic separation column module according to claim 1. Advantageous embodiments are the subject of the dependent claims.

It should be noted that the features listed individually in the claims in any technologically meaningful way, can be combined with each other and show other embodiments of the invention. The description, in particular in connection with the figures, additionally characterizes and specifies the invention.

The separation column module according to the invention for a gas chromatograph comprises a separation column and an electric heater for the separation column. The heater comprises at least one coil and a power supply for generating an alternating magnetic field through the coil and a heating unit. The heating unit is disposed adjacent to the separation column and in the alternating magnetic field generated by the coil so that the separation column is heated by the heating unit. For example, the heating of the separation column takes place by heat radiation and / or heat conduction.

The heating unit according to the invention is characterized in that it comprises a flat, for example plate-shaped, disc-shaped or annular disc-shaped, etc., radiator element which is at least partially electrically conductive and / or magnetizable. Due to the plate-shaped, disc-shaped, ring-shaped, etc., so generally flat design a particularly uniform heat generation and heat distribution over the surface of the radiator element is achieved, which in turn ensures uniform heat transfer to the separation column, for example, by a capillary made of stainless steel or preferably synthetic quartz ("fused silica") is formed.

It is a further advantage of this embodiment that the radiator element heats up homogeneously so that temperature gradients remain small. Thermal stresses in the module are thus avoided. The separation column module also builds very small, since the module is flat according to the invention.

Another advantage of this separation column module is that it produces very little waste heat due to the comparatively low mass heated, is therefore very easy to thermally isolate and also can be cooled comparatively quickly.

The conversion of electrical energy into heat energy takes place depending on the choice of the properties of the radiator element, namely electrically conductive and / or magnetizable, by means of turbulent flow and / or Ummagnetisierungswärme and is therefore not only very efficient, but also allows a spaced arrangement, for example, without material contact, the magnetic field generating coil to the heating unit. It lacks according to the invention advantageously a transformer core.

The heating by eddy currents is based on the fact that eddy currents also experience an ohmic resistance in the radiator element, so that the radiator element heats up. Unlike conventional ohmic heaters but eddy currents run exclusively in the radiator element, so that then can not be spoken of an ohmic heating. In particular, namely, the radiator element is not connected to a power source, but the radiator element is heated directly due to the alternating magnetic field and the induced eddy currents. What proportion of the heat generated by eddy currents on the one hand and the Ummagnetisierungswärme on the other hand on the total heat generated, which causes the alternating magnetic field in the radiator element is irrelevant and depends on the property of the material of the radiator element. The eddy current based heating can be increased by suitable structuring of the surface of the conductive radiator element.

The resulting due to the magnetizability Ummagnetisierungswärme can be effected by an at least partially made of magnetizable material existing element of the radiator element. Preferably, a ferromagnetic element is provided. But it can also be magnetically "hard" materials, for example a layer of magnetite particles in enamel or in a temperature-stable lacquer, for example an inorganic lacquer.

As mentioned above, it is provided in an embodiment according to the invention that the heat is transferred from the heating unit to the separating column by heat conduction, so that a material contact between separation column and heating unit is provided. Material contact according to the invention means that the separation column is directly adjacent to the heating unit or between separation column and heating unit preferably a good heat-conducting body, such as a heat diffuser element, which is explained below, is arranged. In addition, the heat transfer to the separation column can be improved by graphite powder. The "lubrication effect" of the graphite also reduces the mechanical stress on the separation column.The material contact between the separation column and the flat radiator element provides a comparatively large surface area for heat transfer, which enables rapid increases in the temperature of the separation column.

In contrast, however, preferred is an embodiment in which the heat transfer takes place essentially by means of heat radiation, i. the separation column is thus spaced from the heating unit without material contact, or, if present, arranged for the heat diffuser element. The spacing can prevent damage to the separation column, for example when inserting the separation column into the module.

Preferably, the at least one magnetic field generating coil is formed as a flat spiral, that is helical. "Flat" in the sense of the invention means a small thickness of the spiral in the direction perpendicular to the spiral plane compared to the diameter in the plane of the spiral.This structure not only makes the module according to the invention compact, but also allows a homogeneous magnetic field in the vicinity of the coil produce.

Preferably, the coil is wound in one layer in the direction perpendicular to the spiral plane. In this way, it is particularly flat and can be placed close to the radiator element. Preferably, the spiral coil is made of tightly wound, enamel-insulated RF strand. For example, the spiral is out about 10 to 25, more preferably 20 windings formed. For example, the HF strand consists of twisted 120 x 0.1 mm copper lacquer fibers.

Because of the very homogeneous magnetic field and consequent particularly uniform heating, an embodiment is particularly preferred in which the spiral plane of the magnetic field generating coil is parallel to the surface defined by the flat radiator element.

In a further preferred embodiment, to generate a very uniform heating of the radiator element, the at least one alternating magnetic field generating coil and the flat radiator element are formed so that the area covered by the coil and the surface of the radiator element are congruent.

According to a preferred embodiment, the separation column comprises at least one capillary, which is arranged spirally, and whose spiral plane is arranged parallel to the surface defined by the flat radiator element. As a result, on the one hand an efficient and along the capillary uniform heat transfer from the radiator element to the separation column or capillary is achieved, also a compact design is possible.

It is particularly advantageous if the heating unit comprises a first radiator element and a second radiator element and the capillary is arranged between the two radiator elements. In other words, the capillary is then sandwiched between the two radiator elements. This achieves a compact construction. It is particularly advantageous if the two radiator elements adjacent to each associated heat diffuser elements, such as heat diffuser discs, and the capillary is disposed between the heat diffuser elements.

In a further advantageous, because compact design, the separation column comprises a capillary with two spiral-shaped sections which are interconnected in their spiral inside.

According to a preferred embodiment, the separation column module comprises a first and second coil, the latter lying on an axis with the first coil. The heating unit is arranged between the first coil and the second coil. The first coil and the second coil are connected to the power supply so that their magnetic fields add up between them. This results in about an arrangement as Helmholtz coil pair. The advantage of this is that forms a particularly strong magnetic field between the two coils, so that the heating unit can be heated particularly quickly and effectively.

In a further advantageous embodiment, the radiator element comprises at least one heat diffuser element. Heat diffuser element according to the invention, means an element with high thermal conductivity. It is advantageous if the heat diffuser element has a thermal conductivity of more than 200 W / (m K). For example, the heat diffuser element consists essentially of silver, aluminum or copper or alloys thereof. Due to the high thermal conductivity of the heat diffuser element any temperature gradients are compensated in the radiator element, so that the capillary is heated over its longitudinal extent particularly homogeneous to achieve particularly high heating rates.

According to a preferred embodiment, the separation column module comprises a high-frequency power supply for supplying the coil with electric current having a frequency of more than 10 kHz, more preferably in the range of 20 kHz to 10 MHz, more preferably in the range of 30 kHz to 5 MHz. Preferably, the coil is operated in resonance. This improves the efficiency. Furthermore, at such frequencies a particularly large Ummagnetisierungswärme free. The high frequency power supply is particularly simple in construction when the frequency is less than 500 kHz.

The thermal mass is particularly small when the heating unit has a mass of less than 200 g, more preferably less than 100 g.

According to a further preferred embodiment, the heating unit is arranged in a one or more hollow chambers forming, thermal insulating sheath. As a result, a small waste heat is generated, which is important for a temperature-stable operation of several chromatographs in a laboratory.

Preferably, the thermally insulating sheath is made of porous calcium silicate, Made ceramic fiber material or foam glass. Foam glass is a silicate glass by the addition of blowing agents factory-foamed, closed-cell insulation.

The thermally insulating sheath is advantageously provided with at least one opening for forced cooling. For example, channels are incorporated in the enclosure so that a flow of the coolant is directed to the radiator element. This allows the heating unit to be cooled quickly and effectively, for example, by cooled air or liquid nitrogen. Thereby, the temperature working range can be extended, for example to about - 100 to 400 ⁰ C with liquid nitrogen. In addition, the cooling medium heated by the heater can be easily removed from the laboratory to stabilize working conditions and simplify temperature control.

The invention further relates to a gas chromatograph with a separation column module in one of the previously described embodiments. In an advantageous embodiment, it also comprises a temperature measuring device for measuring a temperature at the radiator and an electrical control for regulating the temperature to a predetermined value.

The invention further relates to a process for chromatographic separation in which, using a separation acid module according to the invention in one of the previously described embodiments, the separation column and the stationary phase contained therein are heated by means of the heating unit in order to separate the volatile components contained in the phase from one another, so that they can be characterized by their retention time and quantified by their detection signal.

In the following, the invention will be explained in more detail with reference to an exemplary embodiment. Show

1 shows an inventive separation column module for a gas chromatograph according to the invention in an exploded view;

Figure 2 is a simplified schematic representation of the separation column module according to the invention, in which the heating unit is composed; Figure 3 is a sectional view of the separation column module according to the invention in its arrangement in a thermal insulation.

FIG. 1 shows an inventive separation column module 10 in an exploded view. FIG. 2 is a simplified illustration of the separation column module according to the invention when the heating unit 16 is assembled. The separation column module 10 comprises an electric heater 12 which has a first coil 14.1 and a second coil 14.2. The two coils 14.1, 14.2 are arranged spirally along respective spiral planes S1 and S2. The spiral planes S1, S2 run parallel to one another, so that the coils S1, S2 essentially form a Helmholtz coil arrangement.

Between the coils 14.1, 14.2, a heating unit 16 is arranged, which comprises a first radiator element 18.1 and a second radiator element 18.2. The first radiator element 18.1 comprises a conductive and ferromagnetic element 20.1 made of sheet steel and a heat diffuser element 22.1 made of aluminum sheet. In the same way, the radiator element 18.2 comprises a conductive and ferromagnetic element 20.2 made of sheet steel and a heat diffuser element 22.2 made of aluminum sheet. In addition, reference signs without Zählsuffix denote the respective object as such. It should be noted that in Figure 2, only the outer conductive and ferromagnetic elements are 20.1 and 20.2 made of sheet steel closer.

The ferromagnetic element 20 and the heat diffuser element 22 are each fixedly connected to each other, for example glued, bonded or rolled. The ferromagnetic element 20 and the heat diffuser element 22 have a substantially annular disk shape and correspond in terms of their outer diameter and inner diameter to the corresponding outer and inner diameters of the coils 14. The outer diameter is for example 10 to 25 cm.

Between the two radiator elements 18, a separating column 24 is arranged spirally on a separating plate 28 in each case. In this case, the separating plate 28 made of aluminum and a respective adjacent spacer ring 26 for the to the heating body member 18.1 or to the radiator element 18.2 adjacent arranged separation column 24 each have a receiving chamber. The capillary 24 has two spiral-shaped portions which are wound on the respective side of the separating plate 28 from the outside to the inside and in the spiral inside by a recess in the separating plate 28 are interconnected, as can be clearly seen in the sectional view of Figure 3. The tangentially projecting ends of the capillary 24 are to be connected to the injector and the detector, respectively, and are received in tube ends 29 which are simultaneously provided with seals at these terminals. The capillary 24 extends substantially along a spiral plane S3. In the assembled state, the separation column 24 is at a short distance from the heat diffuser element 22.2 and the heat diffuser element 22.1.

In the assembled state, the conductive and ferromagnetic elements 20, which are made of sheet steel, connected to each other via connecting elements, such as screw, and biased.

Outside the radiator elements 18, the coils 14.1, 14.2 are arranged. In operation, the coils 14.1, 14.2 by means of a not shown high-frequency power supply with an electric current I with a resonance frequency f of the games, for example, about 25 kHz, applied. This leads to eddy currents in the conductive and ferromagnetic elements 20 and to the rapid folding over of the Weiss districts. Through both effects, heat is generated in the conductive and ferromagnetic elements 20, which is released via the heat diffuser elements 22 quickly to the separation column 24 by thermal radiation.

The radiator elements 18.1, 18.2 and the separation column 24 are, as shown in more detail in Fig. 3, arranged in a hollow chamber 31 of a thermally insulating sheath 30. A plurality of apertures 32 are provided in the enclosure 30 to form channels that allow the chamber 31 to flow with a cooling medium as needed, for example, to cool the heating unit 16 after a heating phase. The openings 32 are arranged and / or the chamber 31 is formed so that the radiator elements 18.1, 18.2 are effectively cooled. A likewise not drawn electrical temperature control is connected via a likewise not shown electrical line with the drawn in Figure 1 thermocouple 27 in conjunction and constantly detects the temperature Tist at the capillary 24. The thus detected temperature is compared to a target temperature Tset and the coil 14th so charged with electric current that the actual temperature Tist approaches the target temperature Tsoll as quickly as possible. In the capillary 24, which may have a diameter of, for example, 0.1 mm to 0.35 mm, then the stationary phase to be analyzed is initiated. The fact that the conductive and ferromagnetic elements 20, the Wärmediffu- sor elements 22 and the coils 14 are formed annular disc or plate-shaped, the separation column module 10 is particularly narrow. It has been found that the separation column module is also particularly easy to control and has low energy consumption. For example, the maximum energy consumption of a conventional gas chromatograph is about 2000W, with the separation column module according to the invention comes with about 600W. It is possible to achieve heating rates of 30 ° C / min to even 50 ° C / min with a 200W heating power at a 70% efficiency. The separation column module 10 according to the invention can also have forced cooling, for example via air cooling by means of a fan, a supply of liquid nitrogen or water cooling in order to lower the temperature in the capillary. The cooling times, including stabilization to the initial conditions, can be halved compared to conventional temperature-programmed gas chromatography. For example, in a temperature program typical for oil analysis from 40 ⁰ C to 350 ⁰ C in 20 minutes in conventional gas chromatography with only 10-minute Kühlstabilierzeit at the positively cooled, invention separation column module 10 to be expected, so that about 15% of the cycle time can be saved ,

Claims

claims

A separation column module for a gas chromatograph, comprising a separation column (24) and an electrical heater (12) for the separation column (24), wherein the heater (12) at least one coil (14) and a power supply for generating an alternating magnetic field the coil (14) and further comprising a heating unit (16), wherein the heating unit adjacent to the separation column (24) and in the alternating magnetic field is arranged so that the separation column (24) is heated, characterized in that the heating unit (16) at least a flat radiator element (18) which is at least partially magnetizable and / or electrically conductive.

2. Separation column module according to claim 1, characterized in that the at least one alternating magnetic field generating coil (14) is formed in a flat spiral.

3. Separation column module according to the preceding claim, characterized in that the by the alternating magnetic field generating coil (14) defined spiral plane is parallel to the surface defined by the flat radiator element (18).

4. Trennsäulenmodul any of the preceding claims, characterized in that the at least one alternating magnetic field generating coil (14) and the flat radiator element (18) are formed so that the of the coil (14) covered surface and the surface of the radiator element ( 18) are congruent.

5. Separation column module according to one of the preceding claims, characterized in that the separation column comprises at least one capillary (24) which is arranged spirally and that its spiral plane (S3) is arranged parallel to the plane defined by the flat radiator element (18).

6. Separation column module according to the preceding claim, characterized in that the separation column comprises at least one capillary (24) made of synthetic quartz glass.

7. Separation column module according to one of the preceding claims, characterized in that the heating unit (16) comprises at least two radiator elements (18.1, 18.2) and the capillary (24) between the two radiator elements (18.1, 18.2) is arranged.

8. Separation column module according to one of the preceding claims, characterized in that the capillary (24) comprises two spiral-shaped sections (24) which are interconnected in their spiral inside.

9. Separation column module according to one of the preceding claims, characterized by a first coil (14.1) and a second coil (14.2), which is arranged coaxially with the first coil (14.1), wherein the heating unit (16) between the first coil (14.1) and the second coil (14.2) is arranged.

10. Separation column module according to one of the preceding claims, characterized in that the at least one radiator element (18) comprises a ferromagnetic element (20).

11. Separation column module according to one of the preceding claims, characterized in that the radiator element (18) further comprises at least one Wärmedif- fusor element (22).

12. Separation column module according to one of the preceding claims, characterized in that a high-frequency power supply for supplying the coil (14) with alternating electrical current (I) with a frequency of more than 10 kHz, more preferably in the range of 20 kHz to 10 MHz, still is more preferably provided in the range of 30 kHz to 5 MHz.

13. Separation column module according to one of the preceding claims, characterized in that the heating unit (16) has a mass of less than 200 g, preferably less than 100 g.

14. Separation column module according to one of the preceding claims, characterized in that the heating unit (16) in a at least one hollow chamber (31) forming, thermally insulating sheath (30) is arranged.

15. Separation column module according to the preceding claim, characterized in that the sheath (30) made of porous calcium silicate, of ceramic fibers exhibiting material and / or foam glass is made.

16. Separation column module according to one of the two preceding claims, characterized in that the sheath (30) is provided with at least one opening (32) for a forced cooling.

17. A gas chromatograph characterized by a separation column module (10) according to any one of the preceding claims.

18. Gas chromatograph according to claim 17, characterized by a temperature measuring device (28) for measuring a temperature at the radiator (16) and an electrical control for regulating the temperature to a predetermined value.

19. A method for chromatographic separation characterized by the use of a separating acid module according to any one of claims 1 to 16, wherein the separation column and the stationary phase contained therein is heated by means of the heating unit.