GB2114736A

GB2114736A - Transporting laser-vaporised sample material for analysis

Info

Publication number: GB2114736A
Application number: GB08203688A
Authority: GB
Inventors: Werner Schron
Original assignee: Carl Zeiss Jena GmbH
Current assignee: Jenoptik AG
Priority date: 1980-10-29
Filing date: 1982-02-09
Publication date: 1983-08-24
Also published as: DE3203912A1; DD153921A1; GB2114736B; DD153921B1

Abstract

Samples to be vaporized are carried by a sample holder (15) into an evaporation chamber having a lower cylindrical portion (20) and an upper inverted frusto-conical portion (18). The samples (17) in the holder (15) are subjected to a laser beam from an external laser (12) via a window (11). A carrier gas is led into the lower chamber portion (20) via a non-central opening (22). Carrier gas and vaporized material leaves the upper chamber via an opening (23). Communication between the upper and lower chamber portions takes place by way of an annular gap (21) between the upper chamber portion and the sample holder (15). <IMAGE>

Description

SPECIFICATION Method and device for transporting vapourized sample material The invention relates to a method and a device for transporting vapourized sample material, particularly for use in investigations of element concentrations in solid pulverised sample materials by spectral analysis.

Heretofore, various solutions have been proposed for transporting a laser vapourized sample material in the course of spectral analysis.

In a known arrangement the vapourized sample is removed by suction with flame supplying gases in flame excited spectral analysis procedures. It is, however, disadvantageous that the absence of air tightly sealing does not permit a combined application of the arrangement in flameless and electric excitation spectral analysis. It is not feasible with the known arrangements for spectral analysis to carry out a routine and quantitative analysis of elements by different spectral analysing methods without involving unduly high expenditure.

This is also the case with a further known arrangement having an open vapourizing cell mounted in a form of housing.

This arrangement is disadvantageous since irregularities in the vapourized sample feed due to losses of vapourized sample material reduce the reproducibility of the analysis results.

It is a further disadvantage that the investigations are limited to thin pulverized layers conveyed by an endless belt, apart from the undue expenditure involved by the complicated housing and evaporation cell required. It is an object of the present invention to obviate the above disadvantages.

It is a further object of the invention to provide a method and device for use in routine and direct quantitative spectral investigations of solid sample material and in particular of pulverized samples.

In accordance with the present invention, there is provided a method of transporting vapourized sample material for spectral investigation comprising vapourizing a solid sample material by laser radiation in the absence of air, adding a transporting gas to said vapourized sample material, and circulating said transport gas about said vapourized material whereby to transport said vapourized material by said transporting gas to a spectral investigation device.

The invention also provides a sample cell for use in the aforegoing method, the cell comprising an evaporation chamber having an inlet opening which extends non-centrally into the chamber and is connected to a transport gas supply duct, an outlet opening for connection to an analysing device, a window in the chamber through which laser light can be passed to the chamber, and a sample changer which is adapted to carry a plurality of sample materials in mutually spaced apart receptacles and which is slidably mounted in the chamber for selectively locating the sample materials beneath the window to enable them to be vapourized by the laser light beam.

Advantageously, means for heating the transport gas supply lead are provided to eliminate losses of vapourized sample material.

it is a further advantage when the evaporation chamber comprises a lower cylindrical chamber portion containing said non-central inlet opening, and an upper inverted frusto-conical chamber portion, the narrower end of the upper chamber portion being disposed opposite the upper end of said lower chamber portion and being substantially closed by the sample changer but for a narrow annular nozzle connecting the upper and lower chamber portions.

Use of the present invention permits a combination of laser evaporation on the one hand, and emission and absorption analysis on the other hand and enables use to be made of both procedures in spectroscopic analysis.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example only one embodiment thereof and wherein:- Fig. 1 is a schematic view of an arrangement in accordance with the invention including a device for evaporating a sample material; Fig. 2 is a schematic, partially sectional top view of a sample cell; and Fig. 3 is a schematic section of the apparatus of Fig. 2 on a line x-x.

In Fig. 1 a sample cell 1 is mounted on a microscope stage 2 of a laser micro-analyser (not shown).

The cell is connected on the one hand to a transporting gas source 5 via a duct 3 into which a flow meter 4 is inserted, and on the other hand to a bored graphite rod 7 via a duct 6.

The bored graphite rod 7 opens into a graphite tube 8 to the one end portion of which an excitation source (not shown) and to the other end portion of which a spectral analyser (not shown) are connected in spaced relation, both for use in flameless excitation procedures.

Heaters 9 and 10 are provided around the ducts 3 and 6, respectively. The sample cell 1 is closed by a window 11 which is in spaced relation to a laser 12.

In operation, a transport gas 13 passes from the gas source 5 in appropriate amounts through the duct 3 via the flow meter 4 to the cell 1. The heat 9 pre-heats the gas. The laser 1 2 vapourizes a sample material (not shown) in the cell 1 through the window 12, the vapourized sample material being transported by the gas 1 3 via the pre-heated duct 6 through the graphite rod 7 into the graphite tube 8 where it is analyzed by an atom absorption spectrometer (not shown).

When a flame excited procedure is used the sample material is directed into a flame (not shown).

In Figs. 2 and 3 the sample cell 1 is shown in more detail. The cell 1 comprises a cell housing 14 including an upper frusto-conical evaporation chamber portion 1 8 and a lower chamber portion 20. A longitudinal displaceable sample changer 1 5 is slidingly arranged in and about the longitudinal extension of the cell housing 14 for centrally passing through the housing in an upper region of the lower chamber portion 20 in close relationship with the oppositely located lower end of the upper evaporation chamber 18.

A narrow annular passage 21 (nozzle) connects the upper chamber portion 18 to the lower chamber portion 20. The sample changer 1 5 is provided with circular receptacles 1 6 on its top face for receiving sample material 1 7. The top portion of the upper evaporating chamber 18 is sealed to the external ambient atmosphere by a removable window 11 which is secured by locks 1 9 and which is in spaced opposition to a laser 12.

An inlet opening 22 connected to the gas supply duct 3 for the transporting gas 13 enters non-centrally into the lower cylindrical chamber portion 20. The upper conical evaporation chamber 18 is connected via an outlet 23 to the transporting gas duct 6.

In operation, the transporting gas 13 enters the cylindrical lower chamber portion 20 non-centraliy via the inlet 22 and, due to this arrangement, whirls into the upper evaporation chamber portion 18 through the narrow passage (nozzle) 21.

The upward whirling current of gas 13 is loaded with the sample material 1 7 which has been vapourized by the action of the laser 12, the light flashes of which pass through the window 11 and impinge upon the sample material 1 7. The gas/vapourized sample material mixture leaves the evaporation chamber 18 through the outlet 23 and via the duct 6.

The openings of the outlet 23 and of the inlet 22 are of greater diameter compared with the narrow passage 21 (nozzle) in order to eliminate any uncontrolled expansion of the vaporized sample material at the moment of an impinging laser flash.

The chambers 18 and 20 are tightly sealed relative to the ambient atmosphere by the window 11 and by the sample changer 15 which is in tight engagement with the housing 14 by way of sealing means (not shown). The invention is not restricted to the illustrated embodiment. Thus, for example, the size and geometry of.the receptacles 1 6 can be selected to suit the sample material. It is also feasible to substitute a revolving sample changer for the one shown hereinbefore so that the sample chambers remain closed even when the sample is changed.

Claims

1. A method of transporting vapourized sample material for spectral investigation comprising vapourizing a solid sample material by laser radiation in the absence of air, adding a transporting gas to said vapourized sample material, and circulating said transport gas about said vapourized material whereby to transport said vapourized material by said transporting gas to a spectral investigation device.

2. A sample cell for use in the method of claim 1, comprising an evaporation chamber having an inlet opening which extends noncentrally into the chamber and is connected to a transport gas supply duct, an outlet opening for connection to an analysing device, a window in the chamber through which laser light can be passed to the chamber, and a sample changer which is adapted to carry a plurality of sample materials in mutually spaced apart receptacles and which is slidably mounted in the chamber for selectively locating the sample materials beneath the window to enable them to be vapourized by the laser light beam.

3. A sample cell as claimed in claim 2, including means for heating the transport gas supply lead.

4. A sample cell as claimed in claim 2 or 3, wherein the evaporation chamber comprises a lower cylindrical chamber portion containing said non-central inlet opening, and an upper inverted frusto-conical chamber portion, the narrower end of the upper chamber portion being disposed opposite the upper end of said lower chamber portion and being substantially closed by the sample changer but for a narrow annular nozzle connecting the upper and lower chamber portions.

5. A method of transporting vapourized sample material, substantially as hereinbefore described, with reference to the accompanying drawings.

6. A sample cell for use in the method of claim 5, constructed substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.