Wavelength-dispersive x-ray fluorescence spectrometric determination of selenium in carbonaceous matter of rocks

Selenium is used in producing photocells and exposure meters for photographic use and solar cells, to convert a.c. electricity to d.c. and in rectifiers, for electronic and solid-state applications, in photocopying, to decolourise glass and to make ruby-coloured glasses and enamels, and as a photographic toner additive for stainless steel.

The carbonaceous matter in some sandstones is known to contain selenium. The paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence spectrometric technique for determining selenium in the carbonaceous matter of rocks. The technique uses a sequential x-ray fluorescence spectrometer, 100 kV – 80 mA -3 kW x-ray generator, silver x-ray tube, LiF 220 analysing crystal, fine (150 μm) collimator, air path, scintillation detector, short counting times, and synthetic standards prepared from spectrographically-pure carbon and selenium dioxide.

The accuracy of the technique is excellent (within 0.5 percent) and the precision is also excellent (within 1 percent). The lower limit of detection is 2 ppm. The time taken for determining selenium in a batch of twentyfour samples of the carbonaceous matter of rocks, for a replication of four analyses per sample, by one operator, using a manual wavelengthdispersive x-ray fluorescence spectrometer is only eight hours.