Correction system for spectroscopic determination of trace amounts of cadmium using the atomic Faraday effect with electrothermal atomisation

The effect of background absorption of radiation on the signal obtained in Faraday-effect atomic spectroscopy has been overcome by comparing the energies transmitted when the optical polarisers are in crossed and parallel configurations. Two systems were developed: one was a static system in which a Glan prism was used to divide the optical beam into two beams of orthogonally polarised radiation that were detected by two photomultipliers; the other system used a rotating prism to rotate the plane of polarisation of the optical beam and a single photomultiplier with time-sharing electronics to separate the required signals. Cadmium in a starch matrix was determined using the spectral line at 228.8 nm and losses of incident radiation of up to 99% were corrected successfully.