Determination of inorganic and total mercury by vapor generation atomic absorption spectrometry using different temperatures of the measurement cell

Abstract

A simple and inexpensive laboratory-built flow injection vapor generation system coupled to atomic absorption spectrometry (FI-VG AAS) for inorganic and total mercury determination has been developed. It is based on the vapor generation of total mercury and a selective detection of Hg 2 + or total mercury by varying the temperature of the measurement cell. Only the inorganic mercury is measured when the quartz cell is at room temperature, and when the cell is heated to 650 °C or higher the total Hg concentration is measured. The organic Hg concentration in the sample is calculated from the difference between the total Hg and Hg 2 + concentrations. Parameters such as the type of acid (HCl or HNO 3) and its concentration, reductant (NaBH 4) concentration, carrier solution (HCl) flow rate, carrier gas flow rate, sample volume and quartz cell temperature, which influence FI-VG AAS system performance, were systematically investigated. The optimized conditions for Hg 2 + and total Hg determinations were: 1.0 mol l − 1 HCl as carrier solution, carrier flow rate of 3.5 ml min − 1 , 0.1% (m/v) NaBH 4, reductant flow rate of 1.0 ml min − 1 and carrier gas flow rate of 200 ml min − 1 . The relative standard deviation (RSD) is lower than 5.0% for a 1.0 μg l − 1 Hg solution and the limit of quantification (LOQ, 10 s) is 55 ng g − 1 . Certified samples of dogfish muscle (DORM-1 and DORM-2) and non-certified fish samples were analyzed, using a 6.0 mol l − 1 HCl solution for analyte extraction. The Hg 2 + and CH 3Hg + concentrations found were in agreement with certified ones.