Evaluation of drying conditions of fish tissues for inorganic mercury and methylmercury speciation analysis

Abstract

The influence of drying conditions on the behavior of Hg species (Hg2+ and CH3Hg+) present in fish tissues was evaluated. Drying conditions were evaluated for six fish species using air circulation drying oven in different temperatures (50 to 175°C) and lyophilization (0.25mm Hg, −2°C). Evaluation of drying step was based on losses and conversions of original Hg species after each drying condition. The extraction efficiency was determined by comparing the concentration of total Hg in digested samples (wet digestion in closed system using HNO3) with extracted Hg using l-cysteine solution. Chemical vapor generation-inductively coupled plasma mass spectrometry (CVG-ICP-MS) and liquid chromatography-chemical vapor generation-inductively coupled plasma mass spectrometry (LC-CVG-ICP-MS) were used for the determination of total Hg and Hg species, respectively. The accuracy was evaluated using certified reference materials and an agreement better than 97% with certified values was obtained for CH3Hg+ and total Hg. The relative standard deviation of the proposed method was below 5.5%. Limit of detection of 1.7 and 2.3ngg−1 as Hg was obtained for Hg2+ and CH3Hg+, respectively. Results showed that with drying temperatures above 100°C losses and conversions of CH3Hg+ to Hg2+ can occur for some fish species.