DETERMINATION OF ARSENIC(III) AND ARSENIC(V) BY HYDRIDE GENERATION - ATOMIC-ABSORPTION SPECTROMETRY FOLLOWING A RAPID COPRECIPITATION TECHNIQUE WITH HAFNIUM(IV) HYDROXIDE

Hafnium(IV) hydroxide quantitatively coprecipitates 10-120 ng of arsenic(III) and arsenic(V) from a 100-300 cm3 sample solution at pH 6.0-10.5. After coprecipitation, arsenic(III) can be sensitively determined by heated quartz glass cell atomic absorption spectrometry utilizing arsine generation with sodium tetrahydroborate; arsenic(V) can also be determined in the same manner as above after reducing it to arsenic(III). Interference from hafnium(IV) in the determinations of arsenic (III) and arsenic (V) can be eliminated by using perchloric acid and potassium iodide, respectively. The calibration curves are linear from 0. 5-6.0 ng cm-3 for both arsenic(III) and arsenic(V). Since this method can be used to determine arsenic(III) as well as the sum of the amounts of arsenic(III) and arsenic(V), it is possible to determine arsenic(III) and arsenic(V) consecutively.