From German Patent No. 3,226,235 it is known to produce a volatile sample by adding suitable reagents to a sample material, for example, one or more volatile hydrides of elements like arsenic and others by the addition of reducing agents. The volatile sample is entrained by a carrier gas flow, for instance, an inert gas flow and supplied to the measuring arrangement by means of a carrier gas line or conduit. In the measuring arrangement, the volatile sample contained in the carrier gas flow, is thermally decomposed and there is measured either the absorption or the emission of the atoms formed as the result of the thermal decomposition.
One problem of such known apparatus resides in the fact that the volatile sample is diluted by the carrier gas flow whereby the sensitivity of measurement is considerably impaired.
With regard to a similar apparatus for the analytical determination of volatile elements like mercury, it has been proposed, cf. German Published Patent Application No. 3,830,504.6, published Mar. 15, 1990, to bond the mercury vapor which is present in the carrier gas flow, to a gold wire net by amalgam formation. Subsequently, the amalgam is thermally decomposed by rapid heating by means of, for example, an infrared radiator and the mercury vapor is supplied to the measuring arrangement by the carrier gas flow. In addition to the heating device, there is provided cooling means for cooling down the carrier gas line or conduit as rapidly as possible after heating of the gold wire net in order to thereby render possible a high analysis frequency. The cooling means and the heating device may be series arranged with respect to the flow direction of the carrier gas and the carrier gas line or conduit, on the one hand, and the cooling means and the heating means, on the other hand, may be moveable relative to each other. However, there can also be provided a stationary arrangement in which the cooling means and the heating device are separated from each other during the cooling phase by means of a shield. When using the infrared radiator, the carrier gas line or conduit is made of a material such as fused silica which is transparent for infrared radiation, at least in the region of the gold wire net.
According to a publication by V. Arenas, M. Stoeppler and G. Bergerhoff, entitled "Arsenic determination in the ultratrace range by atomic absorption spectrometry after preconcentration of the hydride", published in Fresenius Zeitschrift fur Analytische Chemie, Vol. 332, pages 447 to 452, 1988, arsenic in the range of 0.05 to 6 ng is determined by atomic absorption spectroscopy using the hydride method. Therefore, the arsenic containing sample is reacted in a hydride reactor with sodium boron hydride and the addition of acid. The thus formed arsine is entrained in a helium current which is dried by freezing out water in a cold trap and which is passed, after the addition of hydrogen, through a further cold trap to the atomic absorption spectrometer. The further cold trap has the form of a U-shaped tube and is cooled to at least -170.degree. C.; it has contained therein a filling of silanized quartz wool at which the arsine is deposited. The cold trap is provided with a heater winding and can be heated from -180.degree. C. to +200.degree. C. in less than 10 seconds.
In accordance with a publication by J. Piwonka, G. Kaiser and G. Tolg, entitled "Determination of selenium at ng/g-and pg/g-levels by hydride generation-atomic absorption spectrometry in biotic materials", published in Fresenius Zeitschrift fur Analytische Chemie, Vol. 321, pages 225 to 234, 1985, selenium in the range of 0.006 to 6 ng is determined by atomic absorption spectroscopy using the hydride method in a manner such that the selenium containing sample is reacted in a hydride reactor with sodium boron hydride and the addition of acid. The thus formed selenium hydride is entrained in an inert gas stream which is passed through an aerosol trap. Thereafter, the selenium hydride containing inert gas stream enters a straight quartz tube which is directly connected to the quartz cuvette of an atomic absorption spectrometer. A section of the straight quartz tube contains a filling of silanized Chromosorb W 30/60 (a diatomaceous earth-based adsorbent used in gas chromatography) or silanized quartz wool. This section is surrounded by an aluminum block cooled by liquid nitrogen. Upon termination of the reaction, the cooled aluminum block is removed and the adsorbed selenium hydride is desorbed by heating the tube section using a water bath or a furnace which is displaceable along the quartz tube. As a result of the abrupt release of the selenium hydride, there are obtained sharp peaks and correspondingly higher sensitivities.
A further publication by F. Alt, J. Messerschmidt and G. Tolg, entitled "A contribution towards the improvement of Se-determination in the pg-region by hydride AAS", published in Fresenius Zeitschrift fur Analytische Chemie, Vol. 327, pages 233 to 234, 1987, relates to a similar system for determining selenium in the pg-region. In this system the adsorption section of the straight quartz tube is located within an electrically heatable steel tube which is present within a liquid nitrogen-filled quartz cooler during adsorption of the formed selenium hydride.
From German Published Patent Application No. 3,233,130, published Mar. 8, 1984, there is known a method of introducing a sample substance in fine distribution into a spectroscopic excitation source like, for example, a flame or plasma. The sample is subject to combustion or evaporation on a sample carrier within a chamber and the thus formed fine particles are drawn into the suction system of the excitation source through a nozzel. The chamber may be defined by a quartz tube in which the sample carrier is displaceably arranged and can be heated to the combustion or evaporation temperature of the sample by means of an infrared radiator.
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