GB1308610A - Apparatus for sequential multielement analysis by atomic spectroscopy - Google Patents

Abstract

1308610 Spectroscopic apparatus TECHNKON INSTRUMENTS CORP 25 Aug 1970 [25 Aug 1969] 42300/69 Heading G1A [Also in Division H1] In atomic fluorescent or emission spectroscopic apparatus, circuitry is provided for sequentially processing signals due to the emissions from different elements, with appropriate processing characteristics for the respective element signals. The signal for one element might, for example, overload the amplifier, so a different amplification is used for each signal. In the fluorescence analysis of a sample, Fig. 1, sources L 1 - L 4 producing bursts of pulses, are energized in turn to excite different elements in the sample 14. While L 1 , for example, is illuminated, switch SW 1 is closed to alter the feedback resistor used in amplifier 20, which is tuned to the frequency of the pulses of the source, the selection of lamp and switch being under control of device 10 which responds to the positioning in front of detector 16 of a particular filter (in this case F 1 ) of wheel 12. The lamps are operated in sequence with suitable intervals therebetween, so that a sequence of sample signals for different elements is obtained on line 22. The apparatus can also be adapted for atomic emission spectroscopy by thermal excitation for which a D.C. amplifier is required. The apparatus may be modified to provide sequential fluorescence and emission test signals, suitable modulation of the radiation from the atomic emission sample being provided or, as in Fig. 2 (not shown), separate filter wheels and amplifiers being provided for the fluorescence and the emission channels. It is stated that a hollowcathode lamp is suitable for the fluorescence analysis and suitable supply conditions for obtaining pulsed output are described (see Division H1). The apparatus may be provided with means for compensating for light source intensity fluctuations, Fig. 4 (not shown). Photo-diodes are associated with the sources and connected in parallel to a tuned amplifier whose output is fed to a ratioing circuit with the output of the main signal processor to give drift-independent signals. The lamp source intensities may be controlled by feedback or by varying the amplifier gains. In the Fig. 2 system, the sample signals may be used to vary the feedback resistors so as to keep the amplifier outputs constant, the resistor values being indicated digitally.