WO2007051653A1

WO2007051653A1 - Method and apparatus for heating of sample material by means of microwaves

Info

Publication number: WO2007051653A1
Application number: PCT/EP2006/010664
Authority: WO
Inventors: Werner Lautenschläger; Martin Metzger; Frank Bismor
Original assignee: Mikrowellen-Systeme Mws Gmbh
Priority date: 2005-11-07
Filing date: 2006-11-07
Publication date: 2007-05-10
Also published as: DE102006014065A1; DE102006014065B4; EP1946616B1; EP1946616A1

Abstract

The invention relates to a method for heating of sample material by means of microwaves, and to an apparatus having a microwave area for heating of sample material. A sample plate (4) with a defined location for a heating element (2) is arranged in the microwave area (70). The heating element (2) is composed of a microwave-absorbent material, and is designed to make direct or indirect contact with the sample material (1). On irradiation with microwaves, the heating element (2) is heated, and passes the heat to the sample material (1). If the intensity of the injected microwaves is reduced, the temperature of the heating element (2) and of the sample material (1) are adapted very quickly, this allowing particularly fast and controlled temperature regulation. An infrared sensor (80) is provided in order to record the temperature. The apparatus is suitable, for example, for determination of drying residue and heat-treatment residue.

Description

Method and apparatus for heating sample material with microwaves

The present invention relates to a method for heating sample material with introduction of microwaves, as well as a device with a microwave chamber for heating sample material.

Such methods and apparatus for treating sample material are known per se from laboratory technology. For example, such devices serve to heat sample material as part of chemical analysis to trigger evaporation events.

For irradiation of the "microwave space" or "treatment space" is usually provided a microwave radiator or microwave transmitter in the form of a magnetron.

The microwave space is usually metallic

Interior walls provided, due to their

Material properties Reflect microwave radiation. So it may be a "microwave oven" so far.

The intensity of the microwave radiation emitted by the microwave radiator can usually be changed, for example, "steplessly", so that influence on the energy input into the microwave space can be taken in. In particular, the absorption of microwaves by an at least partially microwave-absorbing body depends on the intensity of the microwave dependent on him microwave radiation, so that by changing the intensity of the microwave irradiation Influence on the temperature behavior of this body can be taken.

Typically, sample containers or "containers" are provided for receiving sample material, and these containers are placed in the treatment or microwave room with the sample material placed therein, where they are then exposed to microwave irradiation.

If the sample material is itself (at least partially) microwave-absorbing, it will heat upon microwave irradiation by absorbing this radiation. Such a device can thus serve in particular for a treatment of microwave-absorbing sample material.

If the sample material is not or only slightly microwave-absorbing, it can be provided that the sample material is heated indirectly, for example by the sample container consists of microwave-absorbing material. In the case of microwave irradiation, heating of the container thus occurs and the heat produced there is then passed on to the sample material in the container by heat conduction or possibly also by convection.

Of course, a mixed form of the two processes mentioned - direct and indirect heating of the sample material - possible.

In the following, the term "indirect heating" of the sample material is intended to express that the sample material itself is not or only slightly microwaveable and that the heating takes place at least predominantly by absorption of heat from the environment. such as a sample container in which the sample material is located, and / or a gaseous Environment, so for example air, which surrounds the sample material in the microwave space.

In this context, continue to be called _" only slightly microwave absorbing" for the

Sample materials are expressed that the above heating effects by heat absorption from the

Environment in the case of a microwave entry into the

Microwave space over an optionally occurring absorption-induced heating of the sample material itself dominate.

In this context, "indirect heating element" is understood to mean an at least partially microwave-absorbing body which can transfer heat (directly or indirectly via an intermediate body) to the sample material via heat conduction. "At least partially" is intended here to mean that the indirect heating element. In any case, when microwave irradiation is heated more than the sample material, so that a heat flow of the

Heating element in the direction of the sample material is formed.

To determine dry or glow residues, sample material of a known mass is heated or heated in such a way that evaporation or combustion processes occur, through which part of the sample material is released into the environment or burns up or burns. As a result, the mass of the remaining sample material is less than the mass of the original sample material. Subsequently, this remaining mass of the

Specimen determined. These data then allow certain chemical conclusions.

With regard to the timing of the temperature profile of the sample material, it is desirable or advantageous in certain cases that the temperature of the

Sample material in a predetermined manner changes, so that the temperature in the treatment process at least temporarily follows a given or pre-recorded temperature curve, or "temperature curve" .This curve can also be referred to as a "setpoint curve" or "reaction curve".

European Patent EP 0 592 654 B2 discloses a device for evaporating treatment which has a microwave space. Containers are provided for receiving sample material, wherein the containers may consist of a microwave-absorbing material, so that indirect heating of the sample material via the containers is made possible.

The containers may according to this prior art of plastic material, such as PTFE Teflon (polytetrafluoroethylene) exist and are particularly intended as a pressure-stable container.

In this context, however, the following is to be noted with regard to the time course of the temperature of the sample material: Due to the heat capacity of the sample container while the heat in the material of the sample container is stored to a certain extent, so that upon reduction of the microwave irradiation continues heat from the sample container to the sample material per Heat conduction is transmitted. As a result, the above-mentioned tracking of a prescribed temperature curve is made practically impossible, at least in the cases where the predetermined temperature profile has a portion where the temperature increase decreases.

It should also be borne in mind that due to the comparatively material-intensive design of the sample container according to EP 0 592 654 B2, which is necessary because of the pressure stability, the heating of the sample material takes place comparatively slowly because the radiation energy due to the absorption In the sample container material, it must first heat it before the heat can be effectively transferred to the sample material.

Furthermore, the pot-like shape of the container causes "heat build-up" in the region of the sample material, so that the air (or more generally the corresponding gas mixture) in the container heats up, for example as a result of the heat radiation from the container into the interior of the container. As a result, a corresponding adaptation of the temperature of the sample material is generally appreciably delayed as the irradiated microwaves are reduced. This also precludes a precise control of the sample material temperature according to a predetermined reaction curve.

In this context, it should further be considered that, according to EP 0 592 654 B2, at temperatures from about 200 to 500 ^° C., strength problems in the container material can occur.

Of course, said effect can not only occur with pressure-stable sample containers, but in principle also with other containers or otherwise at least partially microwave-absorbing parts which surround the sample material accordingly.

Also, the detection of the temperature of the sample material as z. B. by infrared measurement from the prior art, for. B. from the cited EP 0 592 654 B2 is known, does not change the principles and effects described above. The temperature measured in this way makes it possible to determine with hindsight what time course the temperature of the sample material has taken. However, a precise and reliable control of the temperature profile requires, first of all, that the temperature of the sample material be fast and can be selectively changed. This is contrary to the above effects.

The regulation of the "heating rate" according to the desired curve of not or only slightly microwave absorbing

Sample material is therefore generally only significant

Inaccuracy possible. In general, this leads to a corresponding inaccuracy in an analysis based thereon, depending on the specific application.

The object of the present invention is to specify a method and a device for treating, in particular, no or only insignificantly microwave-absorbing sample material using microwave irradiation, with which or with which the time profile of the temperature of the sample material can be better controlled.

This object is achieved by the features of the independent claims. The dependent claims further form the central idea of the invention in a particularly advantageous manner.

According to the invention, there is provided a method of heating sample material, comprising the steps of: placing the sample material in a microwave space relative to a heating element of microwave absorbing material such that the heating element does not substantially extend beyond the level of the sample material and the sample material is in direct or indirect Wärmeleitkontakt to the heating element. As a further step, the entry of microwaves for heating the heating element is provided.

When irradiated with microwaves, the heating element in the microwave chamber heats up due to its microwave-absorbing properties. Due to the Wärmeleitkontakts then the thus transferring heat from the heating element to the sample material and thus heating the sample material.

Due to the fact that the heating element does not extend at least substantially above the level of the sample material, it is achieved that, after a reduction in the intensity of the microwave radiation radiated into the microwave space, no further heat emission from heat stored in the heating element ("postheating") from the side or As a result, the temperature of the sample material can be adjusted more quickly with microwave reduction.

In addition, it is achieved that the microwave radiation on the way between the transmitter, so z. B. the magnetron and the heating element is not weakened by absorption. This also causes a particularly rapid response of the temperature change of the heating element due to a change in the irradiance.

Furthermore, the heating element can be manufactured with comparatively low cost of materials, so that it has a correspondingly small heat capacity. This is a particularly rapid heating and cooling or general

Temperature adaptation of the heating element and thus also the sample material in response to a change in intensity of the irradiated microwaves possible.

Overall, therefore, by the method according to the invention, the temperature of the sample material can be adapted very quickly when the intensity of the irradiated microwave irradiation changes. The tracking of a setpoint curve is therefore possible with much greater accuracy and faster response. In essence, therefore, a so-called "hysteresis-free" regulation of the temperature of the sample material is effected, whereby under "hysteresis" here the Residue of the temperature adaptation of the sample material to be understood against a change in the microwave irradiation. In other words, the duration of the temperature adjustment is thus shifted to zero.

So that the desired effect can develop, the heating element must therefore not extend "substantially" beyond the level of the sample material, ie it must be ensured that a corresponding free space without heating element is created above this level It can be said that the ratio between a first vertical extension between the support level of the sample material and the level of the upper limit of the heating element to a second vertical extent between this upper limit of the heating element and the upper limit of the microwave space a predetermined value, for example, "1: 1" or "1 : 2 "may not exceed.

In the following, the term "sample support" or "sample holder" is understood to mean a means for holding the sample material in the microwave space. By the term should be expressed that this means may be designed, for example, as a "support", in the sense of "plate" or the like, ie with a substantially flat surface on which the sample material can be easily applied, or but as a "receptacle" in the sense that an edge is provided on a corresponding support, which secures the applied sample material against a lateral breakout.Thus, the "sample support / sample holder" can be a "sample plate" with a flat surface or, for example, a dish-shaped sample receptacle which differs from the sample plate by a certain edge elevation viscous sample in this sense, a "sample recording" is suitable.

The inventive method can be advantageously designed by the sample material is placed on a sample support / sample holder in the microwave space. This makes it possible to keep the upper half space around the sample material free of solids. Through this free space formed the formation of a heat accumulation is avoided. This also contributes to the shortening of the reaction time in the temperature adjustment of the sample material due to a change in the intensity of the irradiated microwave radiation. This of course applies to any solid, regardless of its microwave absorbing property. In particular, therefore, no "cup-shaped" body, for example in the form of side walls of a sample container, must be provided around the sample material. (Also for this clearance, an indication of a minimum vertical extension could be made in analogy to the above statements.)

The sample material may be in direct contact with the heating element or in indirect. For example, a sample support / sample holder itself may be provided as a heating element, on which the sample material is arranged directly. In this case, the heat conduction takes place directly between the heating element in the form of the sample support / sample holder and the sample material. The contact area over which the heat conduction takes place is in this case comparatively large (so to speak "maximum") because it extends over the entire contact surface of the sample material.

In direct Wärmeleitkontakt between the heating element and the sample material, a large contact surface for heat conduction with respect to a rapid heating is obviously advantageous. However, on the other hand, it has to be considered that due to this "big" Contact surface with a reduction of the microwave irradiation a "reheating effect ^w by dispensing the stored heat in the heating element to the sample material is also relatively large, so that a temperature adjustment of the sample material is delayed accordingly in this case.

Advantageously, the sample material is arranged in the microwave space on a sample support / sample holder made of essentially microwave-transparent material. As a result, the shape of the sample supports / sample holder can be optimized independently of the heating element, ie in particular achieve a corresponding increase in surface area for the sample material to be recorded.

Thus, it can be advantageous to provide a sample support / sample holder made of substantially microwave-permeable material on which the sample material is arranged, this sample support / sample holder on the other hand is in direct or indirect Wärmeleitkontakt with the heating element, so that the sample material is in indirect Wärmeleitkontakt to the heating element , The heating element can thereby be optimized independently of the sample support / sample holder in terms of its heat capacity, so in particular be dimensioned such that in the sense of the above representations a particularly rapid temperature adjustment is possible.

Advantageously, a direct contact between the heating element and the sample support / sample holder is produced, because this in turn is advantageous in terms of the fastest possible temperature adjustment. For example, the heating element can be provided below the Probenaufläge / sample holder and the sample support / sample holder, for example, simply be placed on the heating element.

In this case, by shaping the sample support / sample holder on the one hand and the heating element On the other hand, the size of the contact surface for heat conduction are chosen practically freely, so that in this way the heat conduction effect can be influenced.

For example, the contact surface between the sample support / sample holder and the heating element can advantageously be made approximately annular. In this case, the heat at a heat output of the heating element only short propagation paths back to the sample material, so that the heating takes place quickly. On the other hand, with a reduction of the temperature increase or with a temperature decrease of the heating element, the "unwanted" afterheating effect is comparatively low, since the contact surface and therefore the heat conduction effect are comparatively small due to the annular configuration.

Accordingly, in this case, the material of the sample support / sample holder is "substantially" microwave permeable in the sense that the heating of the heating element in microwave irradiation is noticeably faster than the heating of the sample support / sample holder.

The sample support / sample holder is intended to rapidly transfer the heat absorbed via the contact surface to the sample material, so that to that extent a material with a good heat-conducting property is particularly well suited.

For example, for this purpose, a sample support / sample holder may be provided, which consists at least partially of glass fiber and / or quartz fiber material.

Advantageously, the temperature of the sample material or the heating element or the sample support / sample holder is detected. Further advantageously, the temperature detection is carried out during the microwave entry into the microwave space repeatedly. On the basis of this temperature measurement, a temperature curve can be made. Because of the fast Temperature adjustment can be assumed in a detection of the temperature of the heating element that this temperature is virtually representative of the temperature of the sample material.

Advantageously, the intensity of the microwave irradiation is then regulated as a function of the detected temperature.

Advantageously, an air flow takes place in the microwave space. This allows, for example, removal of moisture or solvent vapors.

According to a further aspect of the invention, a device for heating sample material is provided, which has a microwave chamber and a sample support / sample receptacle arranged therein for receiving the sample material. Furthermore, the device has a microwave-absorbing heating element, which in direct or indirect Wärmeleitkontakt with the

Sample support / sample holder is. In this case, the heating element does not substantially extend beyond the level of the sample support / sample holder or, if appropriate, of the sample material located thereon.

The Probenaufläge / sample holder and the heating element may be formed in one piece or two pieces. However, a two-piece embodiment is generally advantageous because, in this case, the heating element and the sample support / sample holder are simply different

Materials can be selected. Advantageously, the sample support / sample holder consists of a substantially microwave transparent material.

In particular, in this case, a material can be selected for the sample supports / sample receptacle that conducts the heat comparatively well (because of the above shown connections) and also as inert as possible, so that undesirable reactions with the resting sample material can be virtually excluded.

In addition, for the sample support / sample holder, a material can be selected which stores comparatively poor heat, that is, has a comparatively low heat capacity, so that even a decrease in temperature or a reduction in temperature increase can take place particularly rapidly and thus supports a fast and easily controllable temperature control becomes. As a material for this example, glass fiber and / or quartz fiber is particularly well.

Advantageously, the sample support / sample holder consists at least partially of a material which has the following properties: (i) it is chemically inert as far as possible in order not to interact undesirably with the resting sample material, (ii) it is in the temperature range intended for the treatment heat resistant, and

(iii) it is lower for the reasons given above

Heat capacity good thermal conductivity. In this sense, the said glass fiber and / or quartz fiber material is particularly suitable.

Preferably, the Probenaufläge / sample holder and the heating element in the microwave space are arranged freely such that the sample support / sample receiving at least substantially laterally and above is not surrounded by microwave-absorbing material. As a result, a change in the intensity emitted by the magnetron results in a corresponding change in the microwave radiation incident on the heating element directly, that is to say in particular without a time delay and without weakening. This also favors a particularly rapid response of the temperature behavior when changing the microwave radiation. It is thus particularly advantageous in this respect if no sample container or the like of a material is arranged around the sample support / sample receiver / heating element arrangement, which at least partially absorbs microwaves.

In addition, with a correspondingly free-standing arrangement coming from the microwave radiator Mikrow.ellens-irradiation unattenuated penetrate into the material of the sample plate holder and cause in this way a particularly rapid heating.

Preferably, therefore, the heating element should be arranged in the microwave space so that its surface is at least partially directly exposed to the microwave radiation, either directly from the microwave radiator or example once (almost lossless) has been reflected on one of the inner walls of the microwave space.

Furthermore, a free space is advantageously formed in the microwave space in the upper half-space around the sample material so that no heat accumulation can form.

In the choice of the material for the heating element, care should be taken in the sense of the above statements that the material has correspondingly appreciable absorption properties with respect to microwave radiation. At very low or too low absorption capacity of the material, the desired rapid heating effect can not form, because then the heating of the heating element is too slow in microwave irradiation. As is known to those skilled in the art, the absorbent properties depend on various factors, such as: B. in particular from the material itself, from the Wavelength (or wavelengths) of the incident radiation and of the temperature.

Advantageously, the heating element consists of a semiconductor material or of an insulator material with finely distributed conductive material, preferably at least partially of silicon carbide. This material is very temperature resistant, for example, it can

System temperatures between room temperature and 1400 ⁰ C can be achieved.

Advantageously, the heating element consists of an inert material.

Advantageously, the heating element is at least substantially sleeve-shaped or ring-shaped or cylindrically shaped. This allows for a total of material-saving design a good and stable support surface for the Probenaufläge / sample holder and also allows to design the contact surface for heat conduction of a suitable size.

An approximately annular contact surface, as it results in a substantially annular or sleeve-like or cylindrical shape of the heating element, is particularly advantageous because in this case, the heat flow must cover only relatively short propagation paths to the entire volume of the sample support / sample holder to penetrate. This in turn allows a particularly rapid spread of heat. For example, it may thus be provided that the sample support / sample holder is approximately circular in horizontal section and the contact surface between the heating element and the Probenaufläge / sample holder is annular, this ring is substantially centric with respect to the sample support / sample holder and has a mean radius, the approximately half the radius of the sample support / sample holder corresponds. The heating element is advantageous at least in its lower

Conically shaped area. For example, it may be formed tapering down, so that on the one hand above a comparatively stable support surface for the

Probenaufläge / sample holder can be formed and on the other hand down insertion into a receiving opening of a magazine or the like is particularly easy.

Advantageously, the heating element is designed as a crucible sleeve.

Advantageously, the device further comprises a temperature measuring device for detecting the temperature of sample material located on the sample support / sample holder and / or for detecting the temperature of the sample support / sample holder and / or for detecting the temperature of the heating element.

Advantageously, the temperature measuring device comprises an infrared sensor. Thus, the temperature can be detected quickly without contact. As a result, the temperature profile can be controlled virtually without loss of time.

With such an infrared sensor, the temperature quasi-permanent, so for example in short time intervals, are detected, which is particularly in connection with the possible rapid temperature change advantage. The results of such a temperature measurement can support a particularly reliable control of the temperature profile act, in particular, because any deviations from setpoints, an immediate countermeasure in the form of a change in the intensity of the microwave radiation can take place.

Advantageously, the device further comprises a means for generating an air flow in the microwave space. The means may comprise, for example, a suction device for removing moisture and / or steam, for example solvent vapor, from the treatment space. For example, it can be provided that the suction device generates a corresponding air flow for shielding the treatment space for this purpose.

Advantageously, the device has a "sample tray" arranged in the microwave space or a "magazine" or the like for receiving the heating element. This magazine can be provided in particular for receiving a plurality of heating elements. Advantageously, the magazine for this purpose have at least one receiving opening for insertion of the heating element. A conical shape of the heating element is advantageous in this respect, because it can be easily inserted from above into such a receiving opening.

The magazine can be made of a microwave-transparent material. However, it is alternatively also possible to design the magazine itself as a "heating element" in the above sense, ie in particular to select a material with correspondingly microwave-absorbing properties for this purpose.

Advantageously, the magazine is rotatably arranged in the treatment room. By rotation, the heating element is generally guided through areas of space, which are more or less permeated by microwave radiation, so that a total of uniform heating is ensured.

The microwave space is advantageously protected on the inside with an insulating material. This can be provided, for example, to protect a microwave metal housing. The insulating material is advantageously microwave transparent and, for example, mounted directly on metallic inner walls of the microwave space. According to another aspect of the invention is a

Provided device for heating sample material. The

Device comprises a microwave space and arranged in the microwave space, for example, microwave-permeable crucible for receiving the

Sample material. Furthermore, the device comprises a microwave-absorbing sleeve for receiving the crucible. The

Sleeve may be provided as a heating element in the sense of the above statements.

According to another aspect of the invention, an apparatus for heating sample material is provided. The device has a microwave space and a sample tray which is arranged in the microwave space. The sample tray may be provided for example in the form of a magazine. The sample tray has at least one defined parking space for a heating element. The parking space can be provided for example by an opening or "receiving opening" in the sample tray

Heating element consists of microwave-absorbing material and is designed for direct or indirect contact with the sample material. The heating element is adjustable in the parking space, for example from above.

The heating element may be provided in the form of a crucible, a sleeve or a crucible sleeve.

According to another aspect of the invention, there is provided a method of heating sample material, the following

Comprising: arranging the sample material relative to at least one heating element of microwave-absorbing material such that the sample material is in direct or indirect heat-conducting contact with the heating element; Setting the heating element, for example from above in a designated space of a sample tray; Arranging the sample tray, the heating element and the sample material in a microwave room; and introducing microwaves to heat the heating element.

Further features, advantages and features will now be explained with reference to a detailed description of an embodiment and with reference to the figures of the accompanying drawings. Show it:

Fig. Ia is a schematic cross section through a sleeve-shaped heating element and a

Sample plate inserted in a magazine or a sample tray,

Fig. / Ib is a schematic cross section through a crucible-shaped heating element and a

Sample plate, inserted in a magazine or a sample tray and

2 shows a schematic cross section through a sample changer system with a

Heating element, inserted in a magazine and with an infrared temperature measuring device.

Fig. Ia shows a schematic cross section through a heating element, which according to this embodiment as

Crucible sleeve 2 is configured and a

Sample support / sample holder in the form of a "sample plate" or a "sample carrier" 5, which is arranged on top of the crucible sleeve 2 and serves for placing sample material 1. In this sense, serves according to this embodiment, the

Heating element also as "sample plate holder." The crucible sleeve 2 is shown in Fig. Ia in a receiving opening 20 of a (only partially shown) magazine 4 recorded or inserted.

Fig. Ib shows a crucible-shaped heating element 2 ', which may be formed conically at least externally. The Sample material 1 can be used directly, or, for example, indirectly, ie, by inserting a temperature-shaped mat 21, for example of glass fiber.

The magazine 4 in this case represents a sample tray and through the receiving opening 20 in the magazine 4 and the sample tray, a defined parking space for the crucible sleeve 2 and the heating element in the magazine 4 and in the sample tray is formed.

The heating element or the example. Outside slightly conical crucible sleeve 2 is adjustable or usable from above into the receiving opening 20 according to this embodiment. However, it can also be provided that the heating element is brought in another way in the intended position on the parking space, for example by lateral insertion. In this case, the receiving opening may for example be provided in the form of a U-shaped recess extending inwardly from the edge of the sample tray.

The crucible sleeve 2 consists of a microwave-absorbing material, the sample carrier 5 of an at least substantially microwave-transparent material. Crucible sleeve 2 and sample carrier 5 are intended to be used in a microwave space or treatment room (not shown in FIG. 1) that is part of a device for treating sample material. The treatment room can be irradiated with a microwave radiator, so for example with a magnetron.

If the crucible sleeve 2 is exposed to microwave irradiation in the treatment room, it heats up due to its microwave-absorbing property. The heat is transmitted through the annular contact or contact surface with the sample carrier 5 by conduction of heat to the latter, so that the sample carrier 5 is heated and in turn the heat to a on the sample carrier 5 resident sample 1 forwarded. The system is thus particularly suitable for sample material 1, which itself is not or only slightly microwaveable.

The crucible sleeve 2 thus consists of a microwave-absorbing material, for example of a ceramic material with embedded therein electrically conductive material, for example of silicon carbide. It is advantageous if the material has comparatively "good" microwave-absorbing properties, because a rapid increase in temperature upon irradiation can then take place This is particularly advantageous with regard to the possibility of rapid temperature control by changing the intensity of the microwave radiation into the treatment space be that at least 50% of the microwave radiation used in the treatment in question is absorbed by the crucible sleeve 2.

The sample carrier 5 can contribute to the enlargement of the surface in the arrangement according to the invention, so that the support surface of the sample carrier 5 can be adapted exactly to the amount of the provided sample material 1. According to the above representations, it is favorable in terms of the choice of the material of the sample carrier 5, to choose a material that conducts the heat well and reacts quickly when reducing the heat, so has a relatively low heat capacity. In addition, of course, the material must withstand the intended temperature range of the system accordingly. For example, this glass and / or quartz fiber material is particularly suitable.

With regard to the material of sample carrier 5 and crucible sleeve 2, it is also advantageous if the most inert

Material is selected to prevent unwanted interactions with the sample material 1 to be treated. Also in In this regard, the specific materials exemplified as silicon carbide and glass / quartz fiber are advantageous.

With the mentioned special materials of the crucible sleeve 2 and the sample carrier 5 according to the embodiment shown here, a temperature range of the system can be handled, which is for example between room temperature and 1400 ⁰ C. The upper limit of this temperature range is particularly particularly influenced by the special choice of the material of the crucible sleeve 2.

The sleeve shape of the crucible sleeve 2 results in particular the following advantages:

(i) Due to the sleeve shape of the crucible sleeve 2, this has a relatively small amount of material, which brings a relatively low heat capacity of the crucible sleeve 2 with it. This makes it possible for heating of the crucible sleeve 2 to take place rapidly upon microwave irradiation and, moreover, a reduction in the temperature increase or a temperature decrease of the crucible sleeve 2, caused by a corresponding reduction in the intensity of the microwave radiation, also takes place particularly quickly. These properties thus allow a particularly rapid "response" of the temperature of the crucible sleeve 2 when changing the microwave irradiation and thus a particularly precise controllable temperature control, which also responds very quickly.

(ii) An approximately annular contact surface between the crucible sleeve 2 and the sample carrier 5 can be formed by the sleeve shape. If the sample carrier 5 is approximately circular in shape, for example in horizontal section, this annular contact surface may be provided approximately in a region which extends around half the radius of the sample carrier 5. This way can work the heat from the crucible sleeve 2 on the sample carrier 5 forward very quickly, because they must cover only relatively short distances in the volume of the sample carrier 5. On the other hand, when the temperature supply is reduced, the temperature of the sample carrier 5 can adjust relatively quickly, because no contact area is formed in relation to the sample carrier 5 over which significant heat would still be transmitted from the crucible sleeve 2 to the sample carrier 5. Thus, a quick and controlled temperature control is favored thereby.

In Fig. 2 is a schematic representation of the device according to the invention is shown. A magazine 4 (or "sample plate") is located in a microwave space 70 with receiving openings 20 into which crucible sleeves can be inserted, the magazine being part of a sample changer or sample changer system.

Evident are two crucible sleeves 2, one of which is inserted into the - with reference to FIG. 2 - right receiving opening of the magazine 4. In the left of the receiving openings 20, another inserted crucible sleeve 2 is shown schematically, on which a sample plate 5 is placed, on which sample material 1 is located. By the conical

Outside shape of the crucible sleeve 2, this can be used in a simple manner in the receiving opening 20 of the magazine 4 from above. Concerning . alternative parking space configurations

(For example, "slot with side slot") is referred to the relevant comments above.

In FIG. 2, only two crucible sleeves 2 and a sample plate 5 are shown for the sake of simplicity and clarity. In practice, of course, it may be provided to provide in each of the receiving openings 20 of the magazine 4 in each case a crucible sleeve 2 with a sample plate 5 arranged thereon. It is particularly advantageous if the sample carrier 5 and the crucible sleeve 2 are arranged so freely in the treatment space 70 that the microwave radiation generated by the microwave emitter 7 is not weakened by microwave-absorbing material on the way to the crucible sleeve 2. In particular, it is therefore advantageous if the crucible sleeve 2 is free of any microwave-absorbing parts, for example in a lateral and upper region.

Furthermore, it is particularly advantageous if there are no parts above the level of the sample material 1 through which a heat accumulation could form around the sample material. Such heat build-up would result in a desired reduction in temperature (or temperature increase) of the sample material that could only be greatly delayed. For example, it may thus be provided that above the level of the sample material - as shown in Fig. 2 - no parts are arranged.

For carrying out the method according to the invention for heating sample material 1 according to this embodiment, therefore, the sample material 1 is arranged in the microwave space 70 on the sample plate 5 and this on the crucible sleeve 2, which serves as an indirect heating element.

Subsequently, the magnetron 7 is turned on, so that microwaves are irradiated into the microwave space 70.

Due to the absorption property of the crucible sleeve 2, the latter heats up and, via the annular contact surface, transfers the heat to the sample plate 5. This heats up quickly due to their good heat-conducting properties and in turn transfers the heat to the sample material 1. With a reduction in the intensity of the irradiated microwave radiation, the temperature of the crucible sleeve 2 is reduced rapidly due to the comparatively low heat capacity thereof. The transfer of heat to the sample plate 5 via the comparatively small, annular contact surface also reduces rapidly, which in turn leads to the temperature of the sample material correspondingly adapting rapidly.

Overall, therefore, the arrangement or the corresponding method, by changing the intensity of the magnetron allows a precise and fast response temperature control of the temperature of the sample material. A given reaction curve can therefore be tracked accordingly. Overall, this invention allows a significant increase in quality with appropriate sample treatments.

The magazine 4 is thus located in a treatment or microwave space 70 into which microwave radiation can be radiated by means of a magnetron 7. The bottom 75 of the treatment space 70 has two access openings 71, 72, wherein the first access opening 71 is provided for the passage of a balance 3, more precisely for the corresponding support of a Aufnähmetlache 35 of the balance 3 and the second access opening 72 for a holder 74 of Magazine 4. •

With further reference to FIG. 2, in this embodiment a motor 61 is provided for rotating the magazine 4 via its support 74. In the sketched

Example, this motor 61 is mounted on a mounting plate 63 which is mounted vertically movable via a parallel guide 66. Another motor 60 is provided for driving an eccentric disk 62, wherein the

Eccentric disc 62 acts from below against the mounting plate 63, so that thereby the mounting plate 63 and thus also the magazine 4 are height adjustable. In this way, a lifting system is formed. By this lifting system, the magazine 4 can be lowered out of the outlined in Fig. 2 position out so that the crucible sleeve 2 comes to rest freely on the Aufnähmetlache 35 of the balance 3 due to their conical outer shape, so that the weight of the crucible sleeve 2 with optionally thereon located sample carrier 5 can be detected with sample material. By the lifting system so a vertical relative movement between the magazine 4 and the crucible sleeve 2 is caused by the crucible sleeve 2 is positioned on the Aufnähmetlache 35 of the balance 3.

For controlling the motors 60, 61 may advantageously be provided a control unit 65 which is connected via data lines to the motors 60, 61 and also the balance 3. Furthermore, the control unit 65 is integrally connected to a data system 40, for example, so that a control and data unit is formed.

The control data, which relate to the motor 61, in particular contain information about the rotational position of the sample tray 4 and thus information about which crucible sleeve 2 is currently at which rotational position and thus, for example, on the balance 3 or its bearing surface 35 , Thus, this information is used for sample identification by means of rotational position coding. The control data related to the motor 60 provide information about the height adjustment of the sample tray 4 and thus information related to a weighing operation of the crucible sleeve 2 with the balance 3.

Temperature measurement:

For detecting the temperature, an infrared temperature sensor 80 is provided. The temperature measurement can take place for example on the weighing position of the crucible sleeve 2 or in the immediate vicinity thereof.

The temperature sensor is inserted in a recess 81 of the metallic wall 90 of the microwave space housing. The temperature sensor can be arranged laterally at the level of a crucible wall and thus measure the sample temperature indirectly via the crucible temperature.

However, the temperature sensor can also be arranged above a crucible (see reference numeral 80 ') so as to be directed directly to sample material and thus to directly detect the sample temperature.

The temperature sensor 80 is also connected to the control and data unit, so that the measured temperature values are also available there.

The various crucibles are therefore rotated past the laterally arranged temperature sensor (measurement as it passes by), the response time of the sensor being matched to the rotational speed and the crucible size Typically, the rotational speed is in the range from 5 to 20 rpm.

A fast IR sensor with a response time of, for example, 50 ms to 100 ms is preferably used. For a faster evaluation, at least one part 82 of the evaluation electronics is preferably arranged in the sensor cable 83.

Since, as stated above, the crucibles and thus the samples are position coded, each temperature measurement can be assigned to a particular sample and in time successive samples are stored to a temperature curve 69 of a sample and optionally displayed on a screen 67. Such a curve can be used to control the temperature to a desired temperature curve by adjusting the microwave power and / or for quality control.

Thus, an individual temperature curve 69, 69 'can be created per sample.

To program the sample position coding, a sample position can be moved in front of the temperature sensor before the MW treatment. The user can then label this sample position by means of the display device 67 and an input device (keyboard, touch screen, etc.) 68.

On the inside, the treatment space 70 may be protected by a microwave permeable insulating layer 90.

Furthermore, a (not shown) suction device may be provided. As a result, for example, moisture and / or solvent vapors can be sucked out of the treatment space 70 by generating a corresponding air throughput.

The sketched in Fig. 2 arrangement is particularly suitable for determining dry or Glückückstand of sample material. In this case, the procedure can advantageously be as follows: In addition to the temperature, the weight change of the corresponding sample material 1 is detected at short time intervals, in each case with the balance 3. From the tare weight of the crucible sleeve 2 and the sample carrier 5 and the weight losses due to volatile components of the sample material, a graphic and tabular evaluation of the volatilizing fractions can then be created. On this basis, a particularly high quality Quality control can be achieved because unforeseen events, such as splashing etc. of sample material are directly visible and an accurate measurement of the sample temperature is possible.

To increase the performance or the accuracy can be provided that multiple scales 3 are used.

Together with the fast microwave control, particularly fast heating rates, drying of sample material by microwave absorption as well as a particularly reliable control can be achieved by a direct tracking of the pre-recorded reaction curve.

In addition to indirect drying of sample material, the device is also suitable for direct drying when a Probenmateriel is used, which is itself microwave-absorbing.

Instead of microwave-absorbing crucible sleeves 2, it is also possible to manufacture the sample tray or the magazine 4 from a microwave-absorbing material.

It should also be mentioned that the crucible sleeves 2 can also be used together with standard crucibles which are inserted into the crucible sleeves. For pure volatilization of even microwave-absorbing sample material in this case, standard crucible made of microwave transparent

Material used.

The advantages of the invention can be summarized as follows:

• It is possible to control the temperature of the sample material very precisely and quickly. • Very fast heating rates are possible.

• The particularly fast response control of the temperature profile when following a given temperature curve results both in temperature increase, as well as in temperature decrease or reduction of the temperature increase.

The invention is suitable, for example, for determining dry residue and incineration residue, wherein the process can be carried out automatically using a sample changer system.

LIST OF REFERENCE NUMBERS

1 sample material

2 crucible sleeve

3 Libra

4 magazine 5 sample plate

7 magnetrons

20 receiving opening

35 Aufnähmetlache the balance

40 Data system 60 Motor for height adjustment of the magazine

61 Motor for rotating the magazine

62 eccentric disc

63 Mounting plate 65 Control unit 66 Parallel guidance

70 treatment room or microwave room

71 first access opening

72 second access opening 74 holder of the magazine 75 bottom of the treatment room

90 insulating layer

Claims

claims

A microwave device for heating sample material comprising

a microwave space (70), a sample tray (4) arranged in the microwave space (70), the sample tray having at least one defined parking space (20) for a heating element (2), the heating element (2) being made of microwave-absorbing material

Material is formed and for direct or indirect contact with the sample material (1) is formed, and wherein the heating element (2) in the parking space (20) is adjustable.

2. Apparatus according to claim 1, characterized in that the heating element (2) can be inserted into the parking space from above or can be set up on the parking space.

3. Apparatus according to claim 1 or 2, characterized in that the heating element is in the form of a crucible or a sleeve.

4. Device according to one of the preceding claims, characterized in that the heating element (2) consists of a semiconductor material.

5. Device according to one of the preceding claims, characterized the heating element (2) consists at least partially of silicon carbide.

6. Device according to one of the preceding claims, characterized in that the heating element (2) consists of an inert material.

7. Device according to one of the preceding claims, characterized by a sample support / sample holder (5), wherein the heating element (2) has a contact surface (85) for thermal contacting with the sample support / sample holder (5).

8. The device according to claim 7, characterized in that the sample support / sample holder (5) has a flat top for receiving the sample material (1).

9. Apparatus according to claim 7 or 8, characterized in that the sample support / sample holder (5) consists of a substantially microwave transparent material.

10. Device according to one of claims 7 to 9, characterized in that the sample support / sample holder (5) consists at least partially of glass fiber and / or quartz fiber material.

11. Device according to one of claims 7 to 10, characterized in that the sample support / sample holder (5) consists of an inert material.

12. Device according to one of the preceding claims, characterized by a temperature measuring device for direct or indirect detection of the temperature of the sample material (1).

13. The device according to claim 12, characterized in that the temperature measuring device comprises an infrared sensor (80).

14. Device according to one of the preceding claims, characterized by

Means (3) for detecting the weight of the sample material (1).

15. Device according to one of the preceding claims, characterized by a lifting device for relative vertical movement between the sample plate (4) and the heating element (2).

16. Device according to one of the preceding claims, characterized by

Means for air flow in the microwave space (70).

17. Device according to one of the preceding claims, characterized in that the microwave space (70) has an insulating layer (90) made of microwave-permeable material.

18. A method of heating sample material, comprising the following steps:

Arranging the sample material (1) with respect to at least one heating element (2) of microwave-absorbing material such that the sample material (1) is in direct or indirect heat-conducting contact with the heating element (2), 3

Setting the heating element (2) in a space provided for this purpose (20) of a sample tray (4),

Arranging the sample tray (4), the heating element (2) and the sample material (1) in a microwave space (70), and

- Entry of microwaves to heat the heating element (2).

19. The method according to claim 18, characterized in that the sample plate (4) consists of substantially microwave-permeable material.

20. The method according to claim 18 or 19, characterized in that in the step "arranging the sample material", the sample material (1) on a sample support / sample holder (5) is applied and the sample support / sample holder (5) in direct WärmeIeitkontakt to the heating element (2) is brought.

21. The method according to any one of claims 18 to 20, characterized in that the temperature of the sample material (1) and / or the heating element (2) is detected.

22. The method according to claim 21, characterized in that the intensity of the microwave irradiation is regulated as a function of the detected temperature.

23. The method according to any one of claims 18 to 22, characterized in that the weight of the sample material (1) is detected.

24. The method according to any one of claims 18 to 23, characterized that in the microwave space (70) air is enforced.

25. A microwave device, comprising: - a microwave space,

a magnetron for irradiating microwaves into the microwave space, and

- An IR temperature sensor, which is arranged in a recess of the metallic microwave space and directed towards the center of the microwave space.