Electrothermal atomisation atomic absorption spectrometric determination of inorganic and methylated arsenic after pre-concentration by hydride generation and trapping the hydrides in a cerium(IV)-iodide absorbing solution

Abstract

A hybrid two-step analytical method for the determination of arsenic is described. Nanogram amounts of environmentally important arsenic species (arsenite, arsenate, monomethylarsonate and dimethylarsinate) are reduced to their corresponding arsines using a slightly modified hydride generation apparatus. The hydrides are then trapped in a small volume of absorbing solution containing 1000 µg ml^–1 of Ce^IV as Ce(NH₄)₂(NO₃)₆ and 800 µg ml^–1 of iodate as Kl, and, finally, arsenic is determined in the concentrate by electrothermal atomisation atomic absorption spectrometry. Cerium(IV) was found to be a very efficient matrix modifier of both inorganic and organic methylated arsenic species. The effect of some instrumental and chemical parameters has been studied and the technique has been applied to the determination of arsenic in mineral water as well as to plant and soil digests.