Determination of soluble chromium(VI) in chromium plating mist by X-ray spectrometry

A wavelength dispersive X-ray fluorescence spectrometry (XRF) method is described for the analysis of soluble chromium(VI) in chromium plating mist collected from workplace air. Calibration of the XRF for soluble chromium(VI) is achieved by using dibenzyldithiocarbamate chromium precipitates prepared from a solution of potassium dichromate. Samples for analysis are collected on PVC filters and directly analysed for total chromium to screen out negative samples. Positive chromium sample filters are then placed in distilled water buffered to pH 4 and the dibenzyldithiocarbamate precipitate of the soluble chromium(VI) is prepared. The precipitate is then collected on a cellulose acetate filter and analysed for chromium(VI) by XRF after mounting between polypropylene film. The procedure was found to be rectilinear up to 100 μg chromium(VI) with a detection limit of 0.04 μg at the 99% confidence limit. Precision studies of the precipitation procedure produced a result of 1.5% coefficient of variation at a level of 20 μg chromium(VI) in water. Interference studies of the procedure showed that chromium(III) did not form a precipitate with the dibenzyldithiocarbamate reagent. Recovery studies of chromium(VI) dust produced results for recovered chromium(VI) between 79% and 95% with a mean recovery of 87%. The method was applied to samples collected from decorative chrome plating works.