Direct determination of arsenic in coal by atomic-absorption spectroscopy using solid sampling and electrothermal atomisation

Abstract

A method using graphite furnace atomic-absorption spectroscopy for the determination of arsenic in coal is described. The analysis may be performed on either a solution of coal or, preferably, by direct atomisation of a slurry of powdered coal. Dissolution of coal is brought about using a mixture of nitric acid, hydrofluoric acid and hydrogen peroxide. Both procedures require matrices of nickel nitrate (volatilisation suppressant) and magnesium nitrate (ashing aid). The arsenic contents of a selection of coals determined by the solution method were in good agreement with certified values and results obtained by other analytical procedures. The solid-sampling technique gave the best results when powdered coal standards of known arsenic content were used for calibration. The analytical characteristics of the method compare favourably with the existing British Standard method, which was shown to give low recoveries for certain coals. The over-all analysis time for the proposed slurry technique is 10 min and the detection limit is less than 0.1 µg g^–1.