Slurry sampling combined with ultrasonic pretreatment for total mercury determination in samples containing inorganic and methylmercury by flow injection-cold vapor-atomic absorption spectrometry

Abstract

A method for the determination of total mercury in solid biological and environmental samples by slurry sampling combined with flow injection-cold vapor-atomic absorption spectrometry (FI-CV-AAS) was developed. The slurries were prepared in 15% m/m nitric acid (mussel tissue, aquatic plant) or a (9 + 1) 15% m/m nitric acid–15% m/m hydrochloric acid mixture (river sediment, sewage sludge) containing 0.02% v/v Triton X-100 as dispersing agent, and subjected to ultrasonic pretreatment before being injected into the FI manifold. Ultrasonic pretreatment of slurries was proved to be necessary in order to improve the low mercury recoveries obtained. The effect of several FI parameters on the effectiveness of cold vapor generation for total mercury determination in slurries of mussel tissue was investigated. Mercury concentrations obtained by the proposed method were compared with those obtained after microwave-assisted digestion of mussel tissue samples. The method was validated against CRM BCR 278 mussel tissue, CRM BCR 60 aquatic plant, CRM BCR 320 river sediment and CRM BCR 145R sewage sludge. LODs were 3, 26, 28 and 8 ng g–1 for mussel tissue, river sediment, sewage sludge and aquatic plant, respectively. The precision, expressed as relative standard deviation [RSD (%)], ranged from 4 to 7% for three replicates of each sample analysed by the standard additions method.