L-CYSTEINE AS A REDUCING AND RELEASING AGENT FOR THE DETERMINATION OF ANTIMONY AND ARSENIC USING FLOW-INJECTION HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY .2. INTERFERENCE STUDIES AND THE ANALYSIS OF COPPER AND STEEL

A method was developed for the determination of antimony and arsenic in copper and steel using flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) and L-Cysteine as reducing and releasing agent. Tolerance limits (less than 10% interference) of at least 250 and 500 mg 1-1 were found for nickel and copper, respectively, in the presence of 1% M/V L-cysteine, in the determination of antimony. For the determination of arsenic the corresponding tolerance limits were 200 mg l-1 for nickel and more than 1000 mg l-1 for copper. Only 100 mg l-1 of copper could be tolerated when potassium iodide was used for reduction. Higher copper concentrations resulted in precipitation of copper(I) iodide, which caused severe contamination of the conduits of the FI system. L-Cysteine is, therefore, recommended for FI-HGAAS because of its better performance for the determination of antimony and arsenic and because of the much lower acid concentrations required. Very good agreement with the certified values for antimony and arsenic in copper and steel National Institute of Standard and Technology Standard Reference Materials was obtained, on addition Of L-cysteine, by calibration with matrix-free standard solutions, using the bracketing technique.