L -Cysteine as a reducing and releasing agent for the determination of antimony and arsenic using flow injection hydride generation atomic absorption spectrometry—Part 1. Optimization of the analytical parameters

L-Cysteine was investigated as the reducing and releasing agent for the determination of antimony and arsenic using flow injection hydride generation atomic absorption spectrometry with the aim of replacing the previously used potassium iodide. The prereduction of the pentavalent to the trivalent form at room temperature was completed within 5 and 30 min for antimony and arsenic, respectively, which was essentially identical with the performance of potassium iodide. However, much lower acid and reagent concentrations were required with L-cysteine than with potassium iodide. In addition, even dilute analyte solutions containing L-cysteine were stable for at least one week, whereas solutions containing potassium iodide had to be prepared fresh daily. Under optimized conditions, in the presence of 1% m/v L-cysteine and 1 mol l–1 HCI for antimony or 0.1 mol l–1 HCI for arsenic, detection limits (three times the standard deviation of a blank solution, n= 10) of 0.05 and 0.01 µg l–1 were obtained for antimony and arsenic. The calibration graphs were linear (r > 0.999) for up to 10 µg l–1 of antimony and 5 µg l–1 of arsenic, using integrated absorbance for evaluation. The precision was better than 2% relative standard deviation (n= 10) for both elements at the 5 µg l–1 concentration level.