AU734744B2 - Longitudinally or transversely heated tubular atomising furnace - Google Patents

Description

Lonqitudinally or transversely heated tubular atomising furnace Description The invention relates to an atomising furnace for spectroscopic purposes which consists of carbon material and is electrically transversely or longitudinally heated, which furnace is assembled from a specially produced tube furnace portion having a sample insertion opening and a specially produced sample carrier, with the tube furnace portion, in whose interior chamber the atomization takes place and which has on the outside contact elements for connection for electrical heating, having a recess for receiving a peg located on the underside of the sample carrier, the recess being in the inside wall at the side lying approximately opposite to the sample insertion opening, and with the sample carrier, which serves for the uptake and delayed vaporisation of the sample to be analysed, being arranged and held in the inside wall of the tube furnace essentially outside the path of the working beam and having, as element for holding it in -the tube furnace portion, a peg extending from its outside wall downwardly to the wall of the tube furnace portion and the sample carrier being held by means of this by insertion in a recess in the wall of the tube furnace part corresponding to the shape of the peg.

Atomising furnaces of this type are preferably used for flameless atomic absorption spectrometry on the basis of graphite tube technology (GF-AAS) for vaporisation and atomisation of solid and liquid samples.

In GF-AAS, the aim is to delay the thermal atomisation of the sample with respect to the heating of the inner chamber of the atomising furnace. This is intended to ensure that the constituents of the sample vaporise under approximately stabilised temperature conditions and are atomised suddenly and cannot precipitate on comparatively cool parts of the walls of the inner atomisation chamber. Attempts have been made to realise this aim in a known way by a sample carrier arranged in the inner furnace chamber. In the ideal case, the sample carrier should for this purpose be constructed and fixed in the furnace in such a way that it is heated neither by heat conduction nor by Joulean heat but instead exclusively by radiant heat from the inside wall of the furnace. An arrangement of a longitudinally heated atomising furnace having a sample carrier, which arrangement, however, fulfilled the above-mentioned requirements only approximately, was suggested for the first time by B. L'vov ("Spectrochimica Acta", Vol. 33B, pp 153 to 193, 1978) The embodiments of sample carriers for longitudinally heated atomising furnaces that are described in the texts of DE-PS 29 24 123, DE-GM 87 14 926.5, DE-OS 37 22 379, DE-GM 88 03 144.6, DE-OS 38 23 346.0 and EP 0 442 009 Al have likewise in detail further essential disadvantages with regard to the above-mentioned requirements.

A further, improved sample carrier for a longitudinally heated atomising furnace is described in DD 233 190 A (DE-OS 35 45 635). It is point-fixed by way of a pin-like support which lies asymmetrically with respect to the centre of the tube furnace and is inserted into a hollow located in the inside wall of the tube furnace. The said sample carrier can, however, be removed again from the tube furnace at any time. One of the stated aims of this protective right application was that atomising furnace and sample -carrier do not form a non detachable unit in the operative final state of production, because the sample carrier itself can be inserted and removed by a manipulator. The result of this is that the position of the sample carrier in the atomising furnace is not positively fixed particularly in the case of shaking or in the presence of strong magnetic fields. Tests by the applicant resulted in uncontrolled wall contacts of the sample carrier and thus current conduction and heat conduction between the outside edges of the sample carrier and the inside wall of the furnace and consequently very unreproducible relationships from measurement to measurement. The sample carrier is designed to receive only small volumes of substance to be analysed 10pl) and is to be produced only from vitreous carbon or pyrocarbon. Vitreous carbon as well as solid pyrolytic carbon can be used as materials for sample carriers to only a limited degree, because the analytical determination of refractory-carbide-forming GF-AAS substances for analysis from surfaces of this type is not possible, the required material purities can be realised only with difficulty and the costperformance relationship is unfavourable for the user.

Transversely heated atomising furnaces have been known since 1987 (DE-GM 87 14 670). EP 0 321 879 A2 describes an atomising furnace having a sample carrier in a longitudinally heated embodiment and in a transversely heated embodiment, which sample carrier is connected to the inside wall of the furnace in a non detachable manner by way of a web which lies symmetrically with respect to the centre of the furnace. Sample carrier and furnace form a material structural unit, which is produced from one crude body.

The sample-holder portion extends only over a central region of the furnace portion. Consequently, there is only a small receiving volume for the substance to be analysed. The connecting web itself has a plurality of transverse bores as a material-reducing measure. An atomising furnace of this type, consisting of a solid graphite blank can be produced only with high technical expenditure. This has a negative effect on the price to the user for this wearing portion.

Sample carriers having supporting rings for transversely heated atomising furnaces in accordance with DE 42 43 767 C2 can likewise be produced only costintensively and with high technical expense, although both sample carrier and furnace can each be produced as a component part.

Object of the Invention It is an object of the present invention to overcome or ameliorate some of the disadvantages of the prior art, or at least to provide a useful alternative.

Summary of the Invention 1o There is firstly disclosed herein an atomizing furnace, comprising: a tube furnace segment defining a furnace chamber and having a sample insertion opening formed therein, said tube furnace segment having contact elements on an outside thereof for electrically heating said furnace chamber; a specimen support produced separately from said tube furnace segment, said Is specimen support being formed with a trough for receiving specimen sample, and including a peg disposed at an underside thereof substantially centrally below said trough; o*o" said tube furnace segment being formed with a recess for receiving said peg of said specimen support, said recess being formed in said chamber substantially centrally •"along a length of said furnace chamber; and said peg of said specimen support being non-releasably secured in said recess.

•ooo• There is further disclosed herein a method of producing an atomizing furnace for use in spectroscopy, the method which comprises: producing a tube furnace segment with a furnace chamber having an inner wall .:surface, with a sample insertion opening, with contact elements on an outside thereof for 25 electrically heating the furnace chamber, and with a recess substantially centrally along a length of the furnace chamber; [R:\LIBLL] 10844spccie.doc:keh producing a specimen support separately from the tube furnace segment, the specimen support having a trough for receiving specimen sample, and a peg disposed at an underside thereof substantially centrally below the trough; inserting the peg of the specimen support into the recess formed in the furnace chamber of the tube furnace segment; and non-releasably securing the peg in the recess and rigidly attaching said specimen support to said tube furnace segment by coating with pyrocarbon all gas-accessible surfaces of the specimen support and the tube furnace segment.

The sample carrier is preferably to be constructed and accommodated in the tube furnace in such a way that during the analysis, there are obtained with this preferred arrangement measured signals which are formed more sharply in comparison with the prior art, and a fast decay of these signals to the noise level of the measuring arrangement takes place, i.e. so that more precise analysis results are achieved than hitherto and a plurality of such precise analysing processes can be carried out one after the other.

The present invention further preferably provides a sample carrier made of a material which permits determinations of the content of all elements which can typically be analysed by GF-AAS, namely 59, to be carried out.

The present invention at least in a preferred embodiment provides the following technical features: The furnace body and the sample carrier consist of electrographite with the same S. or similar physical and chemical properties. They are each produced separately and only then joined together. After the joining together, the gas-accessible surfaces of the oooo, combination sample carrier furnace body are coated with a pyrocarbon layer. As a result of this, the porous surfaces of the electrographite are sealed in a fluid-tight manner.

Not until then is the arrangement ready for use. The sample carrier is constructed as a shell and has on its underside a peg, which is arranged centrally with regard to the longitudinal extent and the transverse extent of said sample carrier and faces the lower portion of the inside wall of the furnace. This peg is inserted into a depression, which complements the shape of the peg and is located in the centre of the longitudinal extent of the inside of the furnace portion, in the furnace wall approximately opposite the sample [RA\LIBLL] IO844speci.doc:kch 6 insertion opening. As a result of the shape of the peg, which is preferably not round, and the depression in the inside wall of the furnace that is complementary thereto, the sample carrier is fixed in the furnace in a form-locking manner, and as a result of the pyrocarbon coating is additionally fixed in a material-locking, well-defined and reproducible manner.

The sample carrier is of minimal mass and its trough-like or shell-like portion preferably extends over as large as possible a portion of the inner furnace chamber available to it.

Where it suffices for achieving the working tasks set, the sample carrier can even have a smaller longitudinal extent. With longitudinally heated furnaces, the sample carrier preferably extends over a region of 50 to 85% of the longitudinal extent of the inner furnace chamber. In transversely heated atomising furnaces, the length of the sample carrier preferably amounts to 75% of the length of the inner furnace chamber and more, and particularly preferably to at least 80%. The walls of the shell-like portion of the sample carrier preferably have a wall thickness of less than 0.5 mm, particularly preferably of less than 0.3 mm. The trough-like or shell-like portion of the sample carrier Is is able to receive up to 50 tl of solution to be analysed in the case of transversely heated furnaces, and up to 40 Vtl of solution to be analysed in the case of longitudinally heated furnaces. All parts are preferably constructed in such a way that their production requires as little expenditure as possible.

The body of the sample carrier at least in a preferred embodiment is essentially 20 constructed from the two function-determining portions peg and sample shell and has a minimum mass, typically, and unlike known solutions, less than 100 mg. The special connection of the sample carrier to the tube furnace by way of a centrally arranged peg, the mass of which has been minimised, in combination with the small mass of the sample o shell, means a considerable reduction in heat conduction. Electrical heating by Joulean heat is anyway excluded in the case of this arrangement. As a result of this, after the desired time-delayed heating of the inside wall of the furnace, a sample to be analysed that is located in the sample shell is heated to atomisation temperature extremely quickly by radiant heat alone. As the absence of memory effects working with the arrangement in accordance with a preferred embodiment of the invention shows (see in this respect 30 Figure the substance to be analysed that is put in is completely vaporised, and after the measurement process is also removed completely from the atomisation zone of the tube furnace.

[R:\LIBLL] 10844specie.doc:keh The shell-like portion of the sample carrier, which is preferably designed to receive volumes of substance to be analysed of up to 50 t, preferably has along its shell base an additional groove having preferably perpendicular walls. This groove serves as an additional obstacle to prevent solutions to be analysed from running off.

The arrangement, in accordance with a preferred embodiment of the invention, of sample carrier and tube furnace can be used both for transversely heated and for longitudinally heated atomising furnaces, and for working with both liquid and solid substances to be analysed without structural alterations to the sample carrier.

As a result of the unalterable fixing of the sample carrier in the tube furnace, which fixing is already carried out by the manufacturer, there are considerable advantages during handling and during working with the analysing arrangement in accordance with at least the preferred embodiment of the invention, because, for example, damage to or incorrect alignments of the sensitive sample carrier are ruled out. When working analytically with the arrangement in accordance with at least the preferred embodiment of the invention, practically no more memory effects are established. It is consequently possible to carry out a large number of analysis procedures one after the other. This results in cost advantages for the user.

By reducing the contact surfaces between the furnace and the sample carrier to a minimum which is technically only just controllable, a considerable improvement in S 20 comparison with the known analysis arrangements (DE-PS 29 24 123; DE-GM 87 14 926.5; DE-OS 37 22 379; DE-GM 88 03 144.6; DE-OS 38 23 346.0; EP 0 442 009 Al) with their comparatively large contact surfaces has been achieved.

The type of fastening, in accordance with at least a preferred embodiment of the o o.o invention, of the sample carrier in the tube furnace additionally ensures a maximum time 25 delay in heating the sample carrier in direct comparison to the heating of the inside wall of the atomising furnace.

The arrangement in accordance with a preferred embodiment of the invention permits the charging of the atomisation of a very large amount of substance to be analysed of up to 50 ptl, in connection with a maximum heating rate of equal to or greater than 2000 K/s. In this connection, the heating occurs after a desired delay with respect to the heating of the inside wall of the furnace.

[R:\LIBLL] I O844specie.doceh By using polycrystalline electrographite of uniform technical quality in order to form the furnace and sample carrier, and as a result of the uniform pyrolytic coating which takes place after mechanical fixing, it is possible to analyse all 59 of the elements of the periodic system that can be analysed with GF-AAS. Only with the analysis of refractory elements such as V, Ti, Si, for example, do small memory effects occur, which can be controlled by known measures.

The analysis arrangement in accordance with a preferred embodiment of the invention effects with analysis operations a good long-term stability of sensitivity and reproducibility (relative standard deviation (RSD) less than 2% for diluted acidic standard solutions) and an extended linear concentration working region with regard to the timeintegrated extinction (surface integral of the signal variation) necessitated by the method.

By using electrographite as basic material for the production of sample carrier and tube furnace and the construction of the portions in a manner suited to rational production, expenditure on production that is lower than that of the prior art is achieved.

From this results a further cost advantage for the user.

The combination of tube furnace portion and sample carrier is constructed in such a way that the sample carrier is arranged inside the tubular portion so as to lie substantially outside the optical beam path and have only place of attachment, which is Slocated on the common central axis of the two portions.

20 In this way, geometrical symmetry of the two components with respect to each other is maximised for transversely heated and for longitudinally heated tube furnaces and So current conduction through the sample carrier is completely avoided. By means of the hollow-shell-like construction of the sample carrier over the greater part of the whole °oo o 2 length of the tube furnace, the introduction and reliable protection of a maximum volume 25 of substance to be analysed is rendered possible.

S: The peg serving to fix the sample carrier in the tube furnace portion advantageously has a non circular cross-section in order to position the sample carrier in a complementary depression in the tube furnace in a manner such that it is protected against torsion. Apart from this, the peg is constructed so as to have at least two steps and only 7 -o the portion thereof that faces the inside wall of the furnace is located in the depression in IR:\LIBLL 10844specie.doc:keh the inside wall of the furnace. The broader portion of the peg rests on the inside wall of the furnace and holds the shell-like portion of the sample carrier at a distance from the inside wall of the furnace. The inside of the peg can have, starting from its lower face, a hollow space, preferably in the form of a circular or oval countersinking. The size of the hollow space and consequently the effectively active cross-sectional area of the peg permit an adjustment of the heat conduction with regard to an optimal delay with respect to time and a minimisation of the total mass of the sample carrier. The place of attachment for this connecting web in the case of longitudinally and transversely heated furnaces is also at the same time in what is relatively speaking the coldest region of the io inside wall of the atomising furnace during the heating process, as published tests by Falk and colleagues ("Spectrochimica Acta", Vol. 40B, pp 533 to 542, 1985) for longitudinally heated furnaces and our own measurements for transversely heated furnaces (see Figure 4) cover.

The chosen arrangement principle consequently ensures as well that the desired time-delayed heating of the sample takes place almost exclusively by radiation energy, which is radiated only from the inside wall of the respective tubular atomising furnace portion.

Brief Description of the Drawings A preferred embodiment of the invention will now be described, by way of S: 20 example only, with reference to the accompanying drawings.

Figure la shows a longitudinal section through an atomising furnace in accordance with an embodiment of the invention; Figure b shows a cross-section through an atomising furnace in accordance with Figure l a, along the sectional plane A-A; Figure 2 shows an opened-up representation of a transversely heated atomising furnace in accordance with an embodiment of the invention; o* .1 Figure 3 shows a plan view of a sample carrier in accordance with an embodiment of the invention; :embodiment of the invention; [R:ALIBLL I 0844specie.doc:keh Figure 4 shows photographs and graphs of the temperature-time curve when heating a transversely heated atomising furnace in accordance with an embodiment of the invention; Figure 5a shows a longitudinal section through an atomising furnace for longitudinal heating or for transverse heating, with an additional longitudinal groove on the base of the sample carrier; Figure 5b shows a cross-section through an atomising furnace in accordance with Figure 5a for the longitudinally heated embodiment; Figure 5c shows a cross-section through an atomising furnace in accordance with Figure 5a for the transversely heated embodiment; Figures 6a and 6b show three-dimensional representations of the sample carrier of an arrangement according to Figure 5a in oblique views from above and from below; Figures 7a and 7b show three-dimensional, cut open representations of atomising furnaces in accordance with Figure 5b, with views onto the shell-like platform of the sample carrier (Figure 7a) and onto the peg and the base of the sample carrier (Figure 7b); Figures 8a and 8b show the representations corresponding to Figures 7a and 7b, :.!but for transversely heated atomising furnaces; Figure 9 shows measurement graphs of test analyses, which were obtained with various types of sample carriers in atomising furnaces.

*OoO o ago o [R\LIBLL] 10844specie.doc:keh 11 Brief Description of the Preferred Embodiments Figure la shows a longitudinal section through a tubular atomising furnace 1 consisting of electrographite coated with pyrocarbon. Located in the tube furnace portion 17 is a sample carrier 2, which is mounted in a recess in the tube furnace portion 17, opposite a sample insertion opening 3 in the tube furnace portion 17, by means of a supporting foot or peg 4. Like the tube furnace portion 17, the sample carrier 2 consists of electrographite and, after it was placed into the tube furnace portion 17, was coated, together with the latter, with pyrocarbon.

The sample carrier 2 has, in its platform 16, a shell-like recess 5 for receiving a sample. The ends 10 of the recess 5 are not so deeply worked, so that edges result which form run-off obstacles for the sample liquid. The peg 4 is constructed in a stepped manner so that an intermediate stage 6 ensures that the *o*o

C

o C.

*o *o*o• o*o *o~ *o o* oo [R:\LIBLL] Io844spmie.doc:keb -12required constant distance from the inside wall of the tube furnace portion 17 is guaranteed.

Figure lb shows a cross-section through the atomising furnace 1 shown in Figure la, along a section line A-A, with contact pieces 7 and 8 for transverse heating being shown to some extent. It can be seen here that, with the exception of the recess 5, the sample carrier 2 has straight side faces 9, which are technically easy to produce.

Figure 2 shows an opened-up representation of a complete transversely heated atomising furnace 1 with the sample carrier 2.

Figure 3 shows a three-dimensional representation of an embodiment of the sample carrier 2 of Figure 2.

The peg or supporting foot 4 has a cross-section which deviates from the circular, in order to avoid mutual torsion when mounting the sample carrier 2 in the tube furnace portion 17.

Figure 4 shows the temperature distribution T (t) of a transversely heated atomising furnace in the embodiment in accordance with the invention as a function of the time during a fast heating process to a predetermined atomisation temperature in the stages tl, t2-and t3. It can be seen that the central zone of the tube furnace is advantageously last to be heated to the desired final temperature.

Figure 5a shows a longitudinal section through a tube furnace portion 17 sample carrier 2 arrangement for longitudinally and transversely heated furnaces, with a further embodiment of a sample carrier 2 in accordance with the invention. In order that the sample to be analysed is received in a secure manner, there is located in the base of the shell-like sample carrier 2 an additional groove 11 which extends over the greater part of the length of the sample carrier 2, is preferably sunk in and has substantially -13perpendicular side walls 12. The base of the groove 11 is preferably formed so as to be level for reasons of ease of production. The peg 4 of the sample carrier 2 has a recess 13, which is advantageously bored or sunk in and preferably extends in the axial direction 18, in order to reduce its thermal conduction further and to minimise the mass of the sample carrier 2. It is particularly advantageous that all of the wall thicknesses 14 do not exceed a dimension of 0.5 mm, as a result of which the total mass of the sample carrier 2 is kept very small.

Figure 5b reproduces a cross-section through the centre of the furnace arrangement according to Figure for the case of a longitudinally heated furnace, while Figure 5c is a corresponding cross-sectional representation for a transversely heated atomising furnace.

Figures 6a and 6b each show a three-dimensional representation of the sample carrier 2 of Figures Sa to Sc in an oblique view from above and an oblique view from below.

Figures 7a and 7b show the sample carrier embodiments 2 in accordance with Figures Sa and 5b as well as Figures Ga, b, in a longitudinally heated tube furnace portion 17 as a three-dimensional, cut open representation.

Figures 8a and 8b show partially cut open, threedimensional representations of a transversely heated atomising furnace 1 with sample carriers 2 in accordance with Figures Sa, 5c, 6a and 6b.

Figure 9 shows absorption signals obtained by means of a furnace arrangement in accordance with the invention in comparison with absorption signals which were obtained with furnace arrangements having sample carriers according to the prior art. The measurements were carried out with a test solution containing 0.1 -14- Ll/ml vanadium in 0.5 HNO (sic). Different absorption signals or absorption curves, as well as the temperature progress in the furnace chamber interior, are shown over the time axis for sample carriers of various embodiments in longitudinally heated atomising furnaces.

Curve 1 resulted from the use of an atomising furnace in accordance with the invention.

Curve 2 was obtained in the case of a measurement using a sample carrier of the "fork platform" type made of solid pyrographite material, in accordance with EP 0 442 009 A.

Curve 3 resulted from the use of a sample carrier in accordance with DD 233 190 A (DE-OS 35 45 635), i.e.

using a sample carrier made of glassy carbon, which is detachably held in a bore in the wall of the tube furnace by means of a peg located on its underside.

Curve 4 resulted from the use of a sample carrier of the "fork platform" type, which was coated with pyrocarbon.

All curves admittedly have the desired temperature delay with respect to time, often also called "platform effect-, in comparison with the heating of the inside wall of the furnace, to the extent that the atomisation signals ("peaks") do not result until after the final temperature state has been reached, but they differ clearly in the construction and decay performance of their signals.

Curve 1 has clearly visible the most sensitive signal and decays as desired to the zero line again within the measuring period of 10 seconds. There are therefore no residues remaining in the furnace. The ratio of signal level to noise level is very high and consequently extraordinarily favourable. As a result of this, a high reproducibility of the measurements is ensured.

Curves 2 and 3 show that the atomisation signal does not decay in practice. Large amounts of the substance to be analysed remain in the analysis arrangement comprising sample carrier and tube furnace, which amounts are gradually vaporised and atomised only after the time available for the analysis. Both the structural form of the sample carrier and also the material from which the analysis arrangement is made are responsible for such a performance. Measurement results of this type cannot be evaluated for analysis purposes, because the analysing process lasts for too long and the result of the subsequent measurement cycle is falsified by residues of substance to be analysed that have not been completely vaporised ("memory effect").

Curve 4 was obtained with an analysis arrangement in which both the sample carrier and the atomising furnace were coated with pyrocarbon. Nevertheless, the atomisation signal which is obtained is much smaller than in Figure 1 and does not decay completely. The reason for this is that the sample carrier is mounted at several points in the furnace and consequently experiences heating which does not come only from the radiation of the inside wall of the furnace. It is namely also heated by undesired electrical transverse heating and increased heat conduction from the inside wall of the furnace. This equally has a damping effect both on signal level and signal area. The signal does not decay completely. Here, as in the case of curves 2 and 3, it can be recognised that not all of the atoms of the substance to be analysed that were inserted into the furnace are completely released in an atomisation cycle and deliver a signal contribution. Therefore, in this case as well, quantitative determinations of elements forming residues, particularly of refractory elements, are not possible with sufficient accuracy.

-16- The measurement graphs of the curves 1 to 4 of Figure 9 show in an impressive way the technical progress achieved by the solution in accordance with the invention.

Claims (21)

1. An atomizing furnace, comprising: a tube furnace segment defining a furnace chamber and having a sample insertion opening formed therein, said tube furnace segment having contact elements on an outside thereof for electrically heating said furnace chamber; a specimen support produced separately from said tube furnace segment, said specimen support being formed with a trough for receiving specimen sample, and including a peg disposed at an underside thereof substantially centrally below said trough; said tube furnace segment being formed with a recess for receiving said peg of said specimen support, said recess being formed in said chamber substantially centrally along a length of said furnace chamber; and said peg of said specimen support being non-releasably secured in said recess.

2. The atomizing furnace according to claim 1, wherein said tube furnace segment and said separately produced specimen support are commonly coated with a Is layer of pyrocarbon deposited thereon after said specimen support and said tube furnace segment were joined together.

3. The atomizing furnace according to claim 1, wherein said specimen support and said tube furnace segment consist of mutually similar material having substantially similar mechanical, physical, and chemical properties.

4. The atomizing furnace according to claim 1, wherein said specimen support and said tube furnace segment consist of identical material having identical mechanical, physical, and chemical properties. .4

5. The atomizing furnace according to claim 1, wherein said specimen support and said tube furnace segment have substantially similar coefficient of thermal S 25 expansion, and substantially similar material characteristic values for porosity and a performance on being coated with pyrocarbon. .eoooi

6. The atomizing furnace according to claim 1, wherein said specimen support and said tube furnace segment are formed of electrographite, and said specimen support and said tube furnace segment have gas-accessible surfaces defined thereon which are coated with pyrocarbon.

7. The atomizing furnace according to claim 1, wherein said recess for S. receiving said peg is formed in said tube furnace segment substantially opposite from said Ssample insertion opening. [R:ALIBLL] 10844specie.doc:keh 18

8. The atomizing furnace according to claim 1, wherein said peg has a cross-section which deviates from circular, and said recess in said tube furnace segment having a complementary shape.

9. The atomizing furnace according to claim 1, wherein said peg has a cross-section discretely decreasing in steps towards the inner wall surface of the tube furnace segment, with at least one of the steps having a larger cross-section than said recess for receiving said peg, for defining a distance between the trough of said specimen support and the inner wall surface of said tube furnace segment.

The atomizing furnace according to claim 1, wherein said specimen support, except for said trough for receiving the specimen samples, is formed with substantially flat faces and substantially straight edges.

11. The atomizing furnace according to claim 1, wherein said tube furnace segment is transversely heated and has a given length, and said specimen support extends over at least 75% of the given length of said tube furnace segment.

12. The atomizing furnace according to claim 1, wherein said tube furnace segment is longitudinally heated and has a given length, and said specimen support extends over 50% to 85% of the given length of said tube furnace segment.

13. The atomizing furnace according to claim 1, wherein said specimen support is formed with walls having thicknesses of< 0.5 mm.

14. The atomizing furnace according to claim 13, wherein said trough is 0 formed in a shell-like portion of said specimen support, said shell-like portion having 0 walls with thicknesses of less than 0.3 mm.

The atomizing furnace according to claim 1, wherein said peg of said specimen support has a downwardly open and axially extending hollow space formed S 25 therein.

16. The atomizing furnace according to claim 1, wherein said trough has a o" odepression formed therein along a deepest zone thereof

17. The atomizing furnace according to claim 16, wherein said depression is a longitudinal groove extending over an entire length of said trough of said specimen o 0 30 support.

18. A method of producing an atomizing furnace for use in spectroscopy, the method which comprises: z' producing a tube furnace segment with a furnace chamber having an inner wall urface, with a sample insertion opening, with contact elements on an outside thereof for [R:\LIBLL I O844specie.dmckeh 19 electrically heating the furnace chamber, and with a recess substantially centrally along a length of the furnace chamber; producing a specimen support separately from the tube furnace segment, the specimen support having a trough for receiving specimen sample, and a peg disposed at an underside thereof substantially centrally below the trough; inserting the peg of the specimen support into the recess formed in the furnace chamber of the tube furnace segment; and non-releasably securing the peg in the recess and rigidly attaching said specimen support to said tube furnace segment by coating with pyrocarbon all gas-accessible surfaces of the specimen support and the tube furnace segment.

19. The method according to claim 18, which comprises forming the tube furnace segment and the specimen support from the same electrographite material in the producing steps.

An atomising furnace substantially as described herein with reference to: Figs. la to 3; Figs. 5a, 6a and 6b; Figs. 5b, 7a and 7b or Figs. 5c, 8a and 8b of the accompanying drawings.

21. A method for the production of an atomising furnace, said method substantially as described herein with reference to: Figs. la to 3; Figs. 5a, 6a and 6b; Figs. 7a and 7b or Figs. 5c, 8a and 8b of the accompanying drawings. Dated 2 April, 2001 SGL Carbon AG Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON J *555 S* [R:\LIBLL]I O844specie.dockeh