GENERATION OF ASH3 FROM AS(V) IN THE ABSENCE OF KI AS PREREDUCING AGENT - SPECIATION OF INORGANIC ARSENIC

It is shown that the potassium iodide to the samples to reduce As(V) to As(III) is not essential when total inorganic arsenic is determined by molecular spectrophotometry (trapping AsH3 in Ag-DDTC) or by atomic-absorption spectrometry (if Ar flow-rate and NaBH4 addition rate are controlled in 6M hydrochloric acid medium). Furthermore, in the presence of low concentration of organic arsenic, a method is reported for the selective determination of inorganic As(III) and As(V), based on the use of citrate/citric acid medium to determine As(III) and hydrochloric acid to determine total inorganic As. As(V) is determined by the difference between total inorganic As and As(III). The interference level of organic arsenic species (monomethylarsenic acid and dimethylarsenic acid) in the determination of total inorganic arsenic and As(III) in 6M hydrochloric acid and citrate/citric acid medium respectively, is reported in the text. The developed method is applied to determine As(III) and As(V) in spiked, tap and waste waters and in lake sediments.