Use of aqueous slurries of coal fly ash samples for the direct determination of As, Sb, and Se by hydride generation-atomic fluorescence spectrometry

A highly sensitive and simple method was developed based on the continuous hydride generation of aqueous coal fly ash slurry samples and the direct atomic fluorescence detection of As, Sb, and Se. A 2(8) x 3/64 Plackett-Burman design was used as the multivariate strategy for evaluation of the effects of several variables involved in hydride generation efficiency (HCl, NaBH4, NaBH4 flow rate, particle size, and slurry concentration). In addition, measurement time was also considered. Slurry concentration was the significant variable for As, hydrochloric acid concentration for Sb determination; no significant variable was found for Se. Optimum values for the significant variables were selected by using univariate approaches. The precision obtained (< 8.0 %) was adequate for the determination of several hydride-forming elements in coal fly ash samples. Since there was a matrix effect, the standard addition method was required. Accuracy was assessed by analyzing NIST 1633b Coal Fly Ash certified reference material. Detection limits within the range of 0.03-0.67 mu g g(-1) were achieved. The developed methods were applied to several coal fly ash samples obtained from a coal-fired power plant.