Determination of total mercury in seafood by cold vapor-atomic absorption spectroscopy (CVAAS) after microwave decomposition

A method was developed for determination of total Hg in seafood using 10% w/v SnCl2 · 2H2O and continuous flow CVAAS after microwave decomposition in closed vessels. Seafoods were decomposed with 5 mL HNO3 and 1 mL 1% w/v NaCl at 200 °C, transferred to polypropylene tubes containing 3.5 mL HCl, and diluted to 50 mL with H2O. Standards were prepared in diluent containing 10% v/v HNO3, 7% v/v HCl, and 0.02% w/v NaCl. Potential interference by 22 elements was evaluated. Interference by Se and Au was observed. Stability of standard solutions in HNO3, HCl and NaCl was evaluated. Stabilizing effect of chloride was demonstrated. Results for six reference materials containing 0.0371-1.59 mg/kg Hg were 86-106% of certificate values. Concentrations in 11 varieties of seafood were 0.015-1.78 mg/kg. Average recoveries of inorganic and organic Hg added to seafood were 102% and 99%, respectively; average recoveries from fortified method blanks were 100% and 97%, respectively. The limits of quantitation were 0.0022 and 0.011 mg/kg in seafoods and reference materials, respectively.