Determination of mercury in concentrated mineral acids by electrothermal atomic absorption spectrometry using gold amalgamation

Abstract

A method for the determination of trace amounts of mercury in concentrated hydrochloric, sulphuric and phosphoric acids by atomic absorption spectrometry at the p.p.b. level has been developed. After reduction of inorganic mercury compounds to mercury vapour, the vapour is transported by an inert gas from the solution and trapped on the gold coated wall of a graphite cuvette. In the second step of the determination, the absorbance signal from the atomisation of mercury released from the amalgam is measured. Peak height and area are both proportional to the mercury level between 5 and 100 p.p.b. with an RSD of up to 15%. Solutions of NaBH₄ or Sn^II were used as reducing agents.