Advanced analytical methods for mercury determination in slightly contaminated water samples

Abstract

This paper presents a comparative study of mercury determination in water samples at low concentrations by 2 different techniques (cold vapour atomic absorption spectrometry, and flow injection analyses system coupled at ICP-EOS). Mono-, divalent mercury and organo-mercury com- pounds are converted to divalent mercury by oxidation with KBrO3–KBr or mixture of potassium permanganate and potassium peroxodisulphate. The solution is then reduced to the elemental form using tin chloride or natrium borohydride in acid medium. For detection of mercury using FIAS ICP-OES technique were applied 2 different pretreatment steps for calibration standards and water samples: a pre-treatment step using a mixture of acids and oxidants (such as sulphuric acid, nitric acid, potassium permanganate, potassium dichromate and potassium peroxodisulphate), heated in an ultrasonic bath (method A), and a pre-treatment step using only hydrocloric acid and potassium bromide/bromate (method B). For reducing step was used 0.3% of NaBH4 in 0.5% NaOH solution. For cold vapour techique coupled with AAS was used a pre-treatment step with hydrocloric acid and oxidation with potassium bromide/bromate (method C). In this case, reducing agent was 10% tin chloride. The analytical performance of both methods have been investigated (detection limit, quantification limit, working range, precision, recovery). The methods are suitable for determination of low mercury content from drinking and mineral water samples.