Selective reduction method for separate determination of inorganic and total mercury in mussel tissue by flow-injection cold vapor technique.

A flow-injection cold vapor atomic absorption spectrometry (FI-CV-AAS) method was developed to determine inorganic mercury and total mercury in mussel samples obtained from the Galicia coasts. The mussel samples were digested in a microwave oven using an HNO3/H2O2 mixture and then total mercury was determined using sodium borohydride as reducing agent. In a separate subsample, following ultrasonic extraction in hydrochloric acid medium, inorganic mercury was determined by selective reduction using stannous chloride in acid medium as reducing agent. The accuracy of the digestion method was checked by analyzing BCR Reference Material No. 278 Mussel Tissue (Mytilus edulis). There were no significant differences between the certified and found concentration values. As a certified reference material of mussel tissue containing both methylmercury and inorganic mercury was not available, recovery studies on mussel tissue samples spiked with inorganic mercury and methylmercury were done to check the reliability of the method. The results revealed that the mercury contained in mussel samples was methylmercury.