Semi-automated determination of lead by hydride generation and atomic-absorption spectrophotometry

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Abstract
The technique of gas-phase atomisation of the volatile hydrides in a heated silica tube and measurement of the resulting atomic-absorption signal has been extended to the determination of lead in air, water and vegetation. The sample solutions, containing 0.7%V/V of nitric acid or 1.0%V/V of perchloric acid, are made to react with 12%V/V hydrogen peroxide solution followed by 4%m/V sodium borohydride solution by means of a peristaltic proportioning pump. The gaseous hydrides generated are swept by a stream of nitrogen into a heated silica tube and the absorbance of lead at 217 nm is recorded. The effects of interferences and their elimination are discussed. Results obtained on a few typical samples by the proposed method and an alternative method are presented. A sensitivity of 0.6 ng ml–1 and a detection limit of 0.1 ng ml–1 have been achieved. The relative standard deviation of the method is 2.5% at a lead concentration of 10 ng ml–1. Up to 50 samples can be analysed in 1 d.

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