CA2231548A1 - Longitudinally or transversely heated tubular atomising furnace - Google Patents
Longitudinally or transversely heated tubular atomising furnace Download PDFInfo
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- CA2231548A1 CA2231548A1 CA002231548A CA2231548A CA2231548A1 CA 2231548 A1 CA2231548 A1 CA 2231548A1 CA 002231548 A CA002231548 A CA 002231548A CA 2231548 A CA2231548 A CA 2231548A CA 2231548 A1 CA2231548 A1 CA 2231548A1
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- sample carrier
- furnace
- atomising
- tube furnace
- sample
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
- G01N21/74—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited using flameless atomising, e.g. graphite furnaces
Abstract
The invention relates to a carbon-material, transversely or longitudinally heated atomising furnace (1) for flameless atomic absorption spectrometry and comprising a tube furnace section (17) and a sample carrier (2) in said tube furnace section. The improvement of the invention is that the sample carrier for fixing in the tube furnace has a central peg or foot (4) which is on the lower surface of said sample carrier and is fixed in a recess which corresponds substantially to the pegform, is in the centre of the inner wall of the tube furnace and substantially opposite the sample input opening. The sample carrier and the tube furnace section consist of electrographite. The gas-accessible surface of the sample carrier and the tube furnace section is coated with pyrocarbon. The two aforementioned parts are undetachably connected to each other in a defined manner by said pyrocarbon coating. The sample carrier preferably extends across the largest possible part of the longitudinal extension of the tube furnace. The surface of the sample carrier has a trough-shaped recess (5) which can hold up to a quantity of 50 µl of analyte solution. The weight of the sample carrier is reduced by structural measures. When functioning, the atomising furnace demonstrates a good level of long-term stability with respect to sensitivity and reproducibility, and a larger linear concentration working range in relation to time-integrated extinction.
Description
CA 02231~48 1998-03-10 '~ . ;
FILE, P~IN THIS ~ NF.~E~
W~T TRANSLAl-l~N G
Lonqitudinally or transversely heated tubular atomisinq furnace Description The invention relates to an atomising furnace for spect:roscopic 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 elect:rical heating, havin~ a recess for receiving a peg located on the underside of the sample carrier, the reces, 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 analy;,ed, 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 furna~e 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 cf the atomising furnace. This is intended to ensure that the constituents of the sample vaporise under approximately stabilised temperature CA 02231~48 1998-03-10 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 re~lise 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 A1 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 appli~ation 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 manip-ulator. The result of this is that the position CA 02231~48 1998-03-10 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 conse~uently very unreproducible relationships from measurement to measurement. The sample carrier is desig-ned to receive only small volumes of substance to be an~lysed (< 10~1) 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-AA,S substances for analysis from surfaces of this type is not possible, the required material purities can be realised only with difficulty and the cost-performance 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 conne~ted 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 furna~e. 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 ~ 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 CA 02231~48 1998-03-10 expencliture. This has a negative effect on the price to the user for this wearing portion.
';ample carriers having supporting rings for transversely heated atomising furnaces in accordance with DE 42 43 767 C2 can likewise be produced only cost-i.ntensively and with high technical expense, although both sample carrier and furnace can each be produced as a component part.
l'he underlying ob-ject of the invention has been to so construct sample carriers and adapt them to the condit:ions in the atomising furnaces surrounding them that t:he above-mentioned technical and analysis defici.encies of the known prior art no longer occur with t:hem in practice. In particular, the sample carrier is to be constructed and accommodated in the tube f.urnace in such a way that during the analysis, there are obtained with this arrangement measured signa]s which are formed more sharply in comparison with t:he prior art, an(1 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.
A further object was to develop in connection with the above-mentioned features of the object a combination of tube fu:rnace - sample carrier made of a material which permits determinations of the content of all e]ements which can typically be analysed by GF-AAS, namely 59, to be carried out.
l'he object is ach:ieved in accordance with the invention by the featu:res of claim 1.
Preferred developments of the solution in accordance with the invention are the subject matter of the dependent claims.
The text of the claims is herewith incorporated CA 02231~48 1998-03-10 into lhe description.
The object is met by the following technical featu-res:
'rhe furnace body and the sample carrier consist of elect-rographite with the same or similar physical and chemical properties. ~hey are each produced separately and only then joined together. After the joining together, the gas-accessible surfaces of the 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 sarnple 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 oppos:ite the sample 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 resull of the pyrocarbon coating is additionally fixed in a rnaterial-locking, well-defined and reproducible manne-r. 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 longiLudinally heated furnaces, the sample carrier prefe:rably extends over a region of 50 to 85~ of the CA 02231~48 1998-03-10 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 parti(~ularly 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 prefe:rably of less than 0.3 mm. The trough-like or shell-like portion of the sample carrier is able to receive up to 50 ~l of solution to be analysed in the case of transversely heated furnaces, and up to 40 ~l of solution to be analysed in the case of longitudinally heated furnaces. All parts are const:ructed in such a way that their production requi:res as little expenditure as possible.
The body of the sample carrier is essentially const:ructed 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 shell, means a considerable reduc_ion 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 memor-y effects working with the arrangement in accordance with the invention shows (see in this respe~t Figure 9), 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.
CA 02231j48 1998-03-10 The shell-like portion of the sample carrier, which is preferably designed to receive volumes of substance to be analysed of up to 50 ~l, 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 the invention, of sa-mple 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 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 the invention, practically-no more memory effects are established. It is consequently possikle 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 comparison with the known analysis arrangements (DE-PS 25~ 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 A1) with their comparatively large contact surfaces has been achieved.
The type of fastening, in accordance with the invention, of the sample carrier in the tube furnace CA 02231~48 1998-03-10 addit.ionally ensures a maximum time 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 the invention permi_s the charging the atomisation of a very large amoun'_ of substance to be analysed of up to 50 ~l, 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.
]3y using polycrystalline electrographite of unifo:rm 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 (JF-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 measu:res.
The analysis arrangement in accordance with the invention effects with analysis operations a good long-ter~ stability of sensitivity and reproducibility (relative standard deviation (RSD) less than 2~ for diluted acidic standard solutions) and an extended linea:r concentration working region with regard to the time-integrated extinction (surface integral of the signal variation) necessitated by the method.
:By using electrographite as basic material for the produ_tion of sample carrier and tube furnace and the construction of the portions in a manner suited to ratio:nal 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 cf tube furnace portion and sample carrier is constructed. in such a way that the sample CA 02231~48 1998-03-10 carrier is arranged inside the tubular portion so as to lie substantially outside the optical beam path and have only one place of attachment, which is located on the common central axis of the two portions.
In this way, geometrical symmetry of the two components with respect to each other is maximized for transversely heated and for longitudinally heated tube furnaces and 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 wh~le length of the tube furnace, the introduction and reliable protection of a maximum volume of substance to be analysed is rendered possible.
The peg serving to fix the sample carrier in the tube Eurnace 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 manne:r such that it is protected against torsion.
Apart from this, the peg is constructed so as to have at least two steps and only the portion thereof that faces the inside wall of the furnace is located in the depression in the insi,~e 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 insi,~e 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 adjuslment 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 longiludinally and transversely heated furnaces is also CA 02231~48 1998-03-10 at the same time in what is relatively speaking the coldest region of the 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.
The invention is explained further in the following by way of example, with the aid of the following drawings, in which:
:Figure la shows a longitudinal section through an atomising furnace in accordance with the invention;
:Figure lb shows a cross-section through an atomising furnace in accordance with Figure la, along the sectional plane A-A;
:Figure 2 shows an opened-up representation of a trans-versely heated atomising furnace in accordance with the invention;
:Figure 3 shows a plan view of a sample carrier in accordance with the invention;
:Figure 4 shows photographs and graphs of the tempe:rature-time curve when heating a transversely heated atomising furnace in accordance with the invention;
:Figure 5a shows a longitudinal section through an atomising furnace for longitudinal heating or for transverse heating, with an additional longitudinal groov~ on the base of the sample carrier;
Figure 5b shows a cross-section through an atomising furnace in accordance with Figure 5a for the CA 02231~48 1998-03-10 longitudinally heated embodiment;
Figure Sc shows a cross-section through an atomising furnace in accordance with Figure 5a for the trans-versely 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 :oelow;
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.
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 CA 0223l~48 l998-03-lO
required constant distance from the inside wall of the tube Eurnace portion 17 is guaranteed.
Figure lb shows a cross-section through the atomi,,ing 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 l_hat, with the exception of the recess 5, the sample carrier 2 has straight side faces 9, which are techn:ically 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 mutua:L torsion when mounting the sample carrier 2 in the tube furnace portion 17.
Figure 4 shows the temperature distribution T (t) of a lransversely heated atomising furnace in the embod:iment in accordance with the invention as a funct:ion of the time (t) during a fast heating process to a I?redetermined 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 :Eurnace 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 g:reater part of the length of the sample carrier 2, is preferably sunk in and has substantially - CA 02231~48 1998-03-10 perpendicular 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 5a for the case of a longitudinally heated furnace, while Figure 5c is a corresponding cross-sectional representation for a transversely heated atomising furna,-e.
Figures 6a and 6b each show a three-dimensional representation of the sample carrier 2 of Figures 5a to 5c 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 5a and 5b as well as Figures 6a, b, in a longitudinally heated tube furnace portion 17 as a three-dimensional, cut open repre,entation.
:Figures 8a and 8b show partially cut open, three-dimensional representations of a transversely heated atomising furnace 1 with sample carriers 2 in accordance with Figures 5a, 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 CA 0223l~48 l998-03-lO
,ul/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 vario-us embodiments in longitudinally heated atomising furna_es.
~ urve 1 resulted from the use of an atomising furnace in accordance with the invention.
_urve 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 ac-cordance 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 furnase by means of a peg located on its underside.
_urve 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.
CA 0223l~48 l998-03-lO
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 gradllally vaporised and atomised only after the time availabLe for the analysis. Both the struct:ural form of the sample carrier and also the material from which the analysis arrangement is made are responsible for such a performance. Measurement result:s 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 fa]sified by residues of substance to be analysed that have not been completely vaporised ("memory effect:").
C'urve 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 radiat:ion 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. rrhis 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 poss:ible with sufficient accuracy.
CA 0223l548 l998-03-lO
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.
FILE, P~IN THIS ~ NF.~E~
W~T TRANSLAl-l~N G
Lonqitudinally or transversely heated tubular atomisinq furnace Description The invention relates to an atomising furnace for spect:roscopic 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 elect:rical heating, havin~ a recess for receiving a peg located on the underside of the sample carrier, the reces, 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 analy;,ed, 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 furna~e 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 cf the atomising furnace. This is intended to ensure that the constituents of the sample vaporise under approximately stabilised temperature CA 02231~48 1998-03-10 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 re~lise 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 A1 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 appli~ation 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 manip-ulator. The result of this is that the position CA 02231~48 1998-03-10 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 conse~uently very unreproducible relationships from measurement to measurement. The sample carrier is desig-ned to receive only small volumes of substance to be an~lysed (< 10~1) 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-AA,S substances for analysis from surfaces of this type is not possible, the required material purities can be realised only with difficulty and the cost-performance 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 conne~ted 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 furna~e. 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 ~ 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 CA 02231~48 1998-03-10 expencliture. This has a negative effect on the price to the user for this wearing portion.
';ample carriers having supporting rings for transversely heated atomising furnaces in accordance with DE 42 43 767 C2 can likewise be produced only cost-i.ntensively and with high technical expense, although both sample carrier and furnace can each be produced as a component part.
l'he underlying ob-ject of the invention has been to so construct sample carriers and adapt them to the condit:ions in the atomising furnaces surrounding them that t:he above-mentioned technical and analysis defici.encies of the known prior art no longer occur with t:hem in practice. In particular, the sample carrier is to be constructed and accommodated in the tube f.urnace in such a way that during the analysis, there are obtained with this arrangement measured signa]s which are formed more sharply in comparison with t:he prior art, an(1 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.
A further object was to develop in connection with the above-mentioned features of the object a combination of tube fu:rnace - sample carrier made of a material which permits determinations of the content of all e]ements which can typically be analysed by GF-AAS, namely 59, to be carried out.
l'he object is ach:ieved in accordance with the invention by the featu:res of claim 1.
Preferred developments of the solution in accordance with the invention are the subject matter of the dependent claims.
The text of the claims is herewith incorporated CA 02231~48 1998-03-10 into lhe description.
The object is met by the following technical featu-res:
'rhe furnace body and the sample carrier consist of elect-rographite with the same or similar physical and chemical properties. ~hey are each produced separately and only then joined together. After the joining together, the gas-accessible surfaces of the 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 sarnple 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 oppos:ite the sample 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 resull of the pyrocarbon coating is additionally fixed in a rnaterial-locking, well-defined and reproducible manne-r. 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 longiLudinally heated furnaces, the sample carrier prefe:rably extends over a region of 50 to 85~ of the CA 02231~48 1998-03-10 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 parti(~ularly 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 prefe:rably of less than 0.3 mm. The trough-like or shell-like portion of the sample carrier is able to receive up to 50 ~l of solution to be analysed in the case of transversely heated furnaces, and up to 40 ~l of solution to be analysed in the case of longitudinally heated furnaces. All parts are const:ructed in such a way that their production requi:res as little expenditure as possible.
The body of the sample carrier is essentially const:ructed 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 shell, means a considerable reduc_ion 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 memor-y effects working with the arrangement in accordance with the invention shows (see in this respe~t Figure 9), 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.
CA 02231j48 1998-03-10 The shell-like portion of the sample carrier, which is preferably designed to receive volumes of substance to be analysed of up to 50 ~l, 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 the invention, of sa-mple 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 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 the invention, practically-no more memory effects are established. It is consequently possikle 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 comparison with the known analysis arrangements (DE-PS 25~ 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 A1) with their comparatively large contact surfaces has been achieved.
The type of fastening, in accordance with the invention, of the sample carrier in the tube furnace CA 02231~48 1998-03-10 addit.ionally ensures a maximum time 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 the invention permi_s the charging the atomisation of a very large amoun'_ of substance to be analysed of up to 50 ~l, 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.
]3y using polycrystalline electrographite of unifo:rm 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 (JF-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 measu:res.
The analysis arrangement in accordance with the invention effects with analysis operations a good long-ter~ stability of sensitivity and reproducibility (relative standard deviation (RSD) less than 2~ for diluted acidic standard solutions) and an extended linea:r concentration working region with regard to the time-integrated extinction (surface integral of the signal variation) necessitated by the method.
:By using electrographite as basic material for the produ_tion of sample carrier and tube furnace and the construction of the portions in a manner suited to ratio:nal 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 cf tube furnace portion and sample carrier is constructed. in such a way that the sample CA 02231~48 1998-03-10 carrier is arranged inside the tubular portion so as to lie substantially outside the optical beam path and have only one place of attachment, which is located on the common central axis of the two portions.
In this way, geometrical symmetry of the two components with respect to each other is maximized for transversely heated and for longitudinally heated tube furnaces and 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 wh~le length of the tube furnace, the introduction and reliable protection of a maximum volume of substance to be analysed is rendered possible.
The peg serving to fix the sample carrier in the tube Eurnace 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 manne:r such that it is protected against torsion.
Apart from this, the peg is constructed so as to have at least two steps and only the portion thereof that faces the inside wall of the furnace is located in the depression in the insi,~e 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 insi,~e 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 adjuslment 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 longiludinally and transversely heated furnaces is also CA 02231~48 1998-03-10 at the same time in what is relatively speaking the coldest region of the 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.
The invention is explained further in the following by way of example, with the aid of the following drawings, in which:
:Figure la shows a longitudinal section through an atomising furnace in accordance with the invention;
:Figure lb shows a cross-section through an atomising furnace in accordance with Figure la, along the sectional plane A-A;
:Figure 2 shows an opened-up representation of a trans-versely heated atomising furnace in accordance with the invention;
:Figure 3 shows a plan view of a sample carrier in accordance with the invention;
:Figure 4 shows photographs and graphs of the tempe:rature-time curve when heating a transversely heated atomising furnace in accordance with the invention;
:Figure 5a shows a longitudinal section through an atomising furnace for longitudinal heating or for transverse heating, with an additional longitudinal groov~ on the base of the sample carrier;
Figure 5b shows a cross-section through an atomising furnace in accordance with Figure 5a for the CA 02231~48 1998-03-10 longitudinally heated embodiment;
Figure Sc shows a cross-section through an atomising furnace in accordance with Figure 5a for the trans-versely 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 :oelow;
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.
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 CA 0223l~48 l998-03-lO
required constant distance from the inside wall of the tube Eurnace portion 17 is guaranteed.
Figure lb shows a cross-section through the atomi,,ing 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 l_hat, with the exception of the recess 5, the sample carrier 2 has straight side faces 9, which are techn:ically 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 mutua:L torsion when mounting the sample carrier 2 in the tube furnace portion 17.
Figure 4 shows the temperature distribution T (t) of a lransversely heated atomising furnace in the embod:iment in accordance with the invention as a funct:ion of the time (t) during a fast heating process to a I?redetermined 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 :Eurnace 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 g:reater part of the length of the sample carrier 2, is preferably sunk in and has substantially - CA 02231~48 1998-03-10 perpendicular 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 5a for the case of a longitudinally heated furnace, while Figure 5c is a corresponding cross-sectional representation for a transversely heated atomising furna,-e.
Figures 6a and 6b each show a three-dimensional representation of the sample carrier 2 of Figures 5a to 5c 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 5a and 5b as well as Figures 6a, b, in a longitudinally heated tube furnace portion 17 as a three-dimensional, cut open repre,entation.
:Figures 8a and 8b show partially cut open, three-dimensional representations of a transversely heated atomising furnace 1 with sample carriers 2 in accordance with Figures 5a, 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 CA 0223l~48 l998-03-lO
,ul/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 vario-us embodiments in longitudinally heated atomising furna_es.
~ urve 1 resulted from the use of an atomising furnace in accordance with the invention.
_urve 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 ac-cordance 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 furnase by means of a peg located on its underside.
_urve 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.
CA 0223l~48 l998-03-lO
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 gradllally vaporised and atomised only after the time availabLe for the analysis. Both the struct:ural form of the sample carrier and also the material from which the analysis arrangement is made are responsible for such a performance. Measurement result:s 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 fa]sified by residues of substance to be analysed that have not been completely vaporised ("memory effect:").
C'urve 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 radiat:ion 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. rrhis 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 poss:ible with sufficient accuracy.
CA 0223l548 l998-03-lO
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 (18)
1. 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, characterised in that the connection point of the sample carrier (2) to the tube furnace portion (17) is located in the centre of the lengthwise extension of the furnace chamber interior and that the peg or foot (4) of the sample carrier (2) extends from the centre of the sample carrier (2) downardly into the recess corresponding to this peg or foot (4) and which is in the inside wall of the tube furnace portion (17) and is non-releasably secured there
2. Atomising furnace according to claim 1 characterised in that sample carrier (2) and tube furnace portion (17) have a commonly deposited layer of pyrocarbon, which was deposited after the sample carrier (2) and tube furnace portion (17) were joined together.
3. Atomising furnace according to one of claims 1 or 2, characterised in that sample carrier (2) and tube furnace portion (17) consist of a similar material or the same material and have the same or similar mechanical, physical and chemical properties.
4. Atomising furnace according to one or more of the claims 1 to 3, characterised in that sample carrier (2) and tube furnace portion (17) have the same or similar material characteristic values for the coefficient of thermal expansion, the porosity and the performance when coated with pyrocarbon.
5. Atomising furnace according to one or more of claims 1 to 4, characterised in that the sample carrier (2) and the tube furnace portion (17) consist of electrographite, and in that the gas-accessible surfaces of sample carrier (2) and tube furnace portion (17) are coated with pyrocarbon.
6. Atomising furnace according to one or more of claims 1 to 5, characterised in that the support and connection point of the sample carrier (2) to the tube furnace portion (17) is located opposite a sample insertion opening (3).
7. Atomising furnace according to one or more of claims 1 to 6, characterised in that the peg (4) for fixing the sample carrier (2) in the tube furnace portion (17) has a cross-section which deviates from the circular, and in that this peg (4) is inserted into a complementary depression in the inside wall of the tube furnace portion (17).
8. Atomising furnace according to one or more of claims 1 to 7, characterised in that the peg (4) has a cross-section (6) which decreases in steps in the direction of the inside wall of the tube furnace portion (17), with at least one of the these steps (6) having a larger cross-section than the opening for receiving the peg (4) in the inside wall of the furnace, and in this way a defined distance between the portion of the sample carrier (2) that receives the samples for analysis and the inside wall of the furnace being guaranteed.
9. Atomising furnace according to one or more of claims 1 to 8, characterised in that, with the exception of a shell-like recess (5) intended for receiving the samples for analysis, the portion forming the platform (16) of the sample carrier (2) has straight faces and edges.
10. Atomising furnace according to one or more of claims 1 to 9, characterised in that the atomising furnace (1) is intended for transverse heating and the shell-like portion (5) of the sample carrier (2) that receives the samples for analysis extends over at least 75% of the length of the tubular portion of the atomising furnace (1).
11. Atomising furnace according to one or more of claims 1 to 9 characterised in that the atomising furnace (1) is intended for longitudinal heating and the shell-like portion (5) of the sample carrier (2) that receives the samples for analysis extends over a region of 50 to 85% of the length of the tubular portion of the tube furnace (17).
12. Atomising furnace according to one or more of claims 1 to 11, characterised in that the walls of the sample carrier (2) have thicknesses of 0.5 mm or less.
13. Atomising furnace according to claim 12, characterised in that the walls of the shell-like portion (5) of the sample carrier have thicknesses of less than 0.3 mm.
14. Atomising furnace according to one or more of claims 1 to 13, characterised in that the peg (4) of the sample carrier (2) has a hollow space (13) which is open towards the bottom and extends in an axial direction (18).
15. Atomising furnace according to one or more of claims 1 to 14, characterised in that the sample carrier (2) has a hollow (11) in the region of the deepest zone of the shell-like recess (5) intended for receiving the sample for analysis which is in the form of a bore or a groove.
16. Atomising furnace according to claim 15, characterised in that the depression (11) is a longitudinal groove which extends over the whole length of the shell-like hollow (5) of the sample carrier (2).
17. Method for the production of an atomising furnace in accordance with claim 2, characterised in that - in a first step, the tube furnace portion (17) of the atomising furnace (1) and the sample carrier (2) intended for insertion into the tube furnace portion (17) are produced separately, - in a second step, the peg (4) of the sample carrier (2) is inserted into the peg opening provided therefor in the inner chamber of the tube furnace portion (17), and - in a third step, the gas-accessible surface of the atomising furnace (1), which is obtained by assembly according to step 2 and consists of tube furnace (17) and sample carrier (2), is coated with pyrocarbon and as a result of this, the sample carrier (2) is connected to the tube furnace portion (17) of the atomising furnace (1) in a non detachable manner.
18. Method for the production of an atomising furnace according to claim 17, characterised in that the same electrographite material is used for the production of the tube furnace portion (17) and the sample carrier (2) in accordance with step 1.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE29612065U DE29612065U1 (en) | 1996-07-11 | 1996-07-11 | Cross-heated tubular atomizing furnace |
| DE29612065.0 | 1996-07-11 | ||
| DE19716492.7 | 1997-04-19 | ||
| DE19716492A DE19716492A1 (en) | 1996-07-11 | 1997-04-19 | Longitudinal or cross-heated tubular atomizing furnace |
| PCT/EP1997/003500 WO1998002733A1 (en) | 1996-07-11 | 1997-07-03 | Longitudinally or transversely heated tubular atomising furnace |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2231548A1 true CA2231548A1 (en) | 1998-01-22 |
Family
ID=26035921
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002231548A Abandoned CA2231548A1 (en) | 1996-07-11 | 1997-07-03 | Longitudinally or transversely heated tubular atomising furnace |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0877928A1 (en) |
| AU (1) | AU734744B2 (en) |
| CA (1) | CA2231548A1 (en) |
| WO (1) | WO1998002733A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19932874C2 (en) * | 1999-07-16 | 2002-11-14 | Schunk Kohlenstofftechnik Gmbh | atomizing furnace |
| DE102016219492A1 (en) * | 2016-10-07 | 2018-04-12 | Schunk Kohlenstofftechnik Gmbh | Sample carrier for an atomizing furnace and method of manufacture |
| CN112080619A (en) * | 2020-08-14 | 2020-12-15 | 中国石油天然气集团有限公司 | Tube furnace with adjustable cooling speed and working method thereof |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3416421A1 (en) * | 1984-05-04 | 1985-11-07 | Philips Patentverwaltung Gmbh, 2000 Hamburg | SAMPLE CARRIER FOR THE FLAMELESS ATOMIC ABSORPTION AND EMISSION SPECTROSCOPY AND METHOD FOR THE PRODUCTION THEREOF |
| DD233190A1 (en) * | 1984-09-28 | 1986-02-19 | Adw Der Ddr Zi F Optik U Spekt | ATOMIZER FOR SAMPLE SUPPLIERS |
| DE3726533A1 (en) * | 1987-08-10 | 1989-02-23 | Bodenseewerk Perkin Elmer Co | CONTACT ARRANGEMENT FOR THE POWER SUPPLY TO A FURNACE IN THE ATOMIC ABSORPTION SPECTROSCOPY |
| DE3743286A1 (en) * | 1987-12-19 | 1989-06-29 | Bodenseewerk Perkin Elmer Co | OVEN FOR THERMOELECTRIC ATOMIZATION |
| DE8803144U1 (en) * | 1988-03-09 | 1988-04-21 | Ringsdorff-Werke Gmbh, 5300 Bonn, De | |
| DE3823346C2 (en) * | 1988-07-09 | 1994-03-24 | Ringsdorff Werke Gmbh | Graphite furnace with a sample holder for atomic absorption spectroscopy |
| DE3923822C2 (en) * | 1989-07-19 | 1998-08-20 | Bodenseewerk Perkin Elmer Co | Furnace for the electrothermal atomization of samples for spectroscopic purposes and process for its manufacture |
-
1997
- 1997-07-03 EP EP97930496A patent/EP0877928A1/en not_active Withdrawn
- 1997-07-03 WO PCT/EP1997/003500 patent/WO1998002733A1/en active Application Filing
- 1997-07-03 CA CA002231548A patent/CA2231548A1/en not_active Abandoned
- 1997-07-03 AU AU34426/97A patent/AU734744B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| EP0877928A1 (en) | 1998-11-18 |
| WO1998002733A1 (en) | 1998-01-22 |
| AU734744B2 (en) | 2001-06-21 |
| AU3442697A (en) | 1998-02-09 |
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| Date | Code | Title | Description |
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| FZDE | Discontinued |