Determining Total Mercury in Samples from the Persian Gulf and the Caspian Sea: Comparison of Dry Ash and Wet Extraction Mothods

Monitoring of mercury in environmental samples, with its proven toxicity on the food chain, requires sensitive and accurate analytical techniques. In this study, two methods for identification and quantification of total mercury in biological and sediment samples are compared: i) dry ash preparation and subsequent established procedures for Combustion Atomic Absorption Spectrometry, (AMA 254) and ii) wet extraction consisted of classical and microwave oven digestion methods combined with cold vapor Atomic Absorption (CV AAS) analyzing method. In order to compare the accuracy of the methods for total mercury determination, biological and sediment certified Reference Materials and environmental samples were analyzed. The precision and accuracy of the applied analytical methods were compared on eight Certified Reference Materials, Dorm2, Dolt 2 and Tort 2, trace metals in dog fish muscle, liver and Lobster (provided by the national research council of Canada); NIST 1556a, NISTt-2976, IAEA 142 trace metals and mercury in oyster, mussels and fish, respectively; IAEA 086 and IAEA405 trace elements in hair and in polluted estuary sediment (provided by international Atomic Energy), respectively. Ten environmental (fish and sediment) samples and one inter-comparison sample (BCR 710, Total and methylmercury in oyster tissue) as well as certified samples were analyzed in six replications. The detection limits (DLs) in the combustion AAS (AMA), CEM (MDS 2000) microwave oven CVAAS, CEM (Mars 5) microwave oven CV AAS and in normal oven CV AAS for biological and sediment were compared. The AMA 254 with lower detection and quantification limits was more sensitive analyzing method in comparing with the other methods.