Organic and total lead in selected fresh and canned seafood products

Various fresh and canned seafood products were examined for ionic alkyl lead, tetraalkyl lead and total lead. Dimethyl lead, diethyl lead, trimethyl lead and triethyl lead were extracted with diphenylthiocarbazone (dithizone) at pH 8 and 9 from enzymically hydrolysed samples. Butyl derivatives were formed by Grignard reaction prior to analysis by gas chromatography-atomic absorption spectrometry (GC-AAS). Tetraalkyl lead was extracted from the hydrolysates with hexane. Total lead was determined by reductive coprecipitation with palladium in the presence of ascorbic acid after nitric-perchloric digestion. Many of the samples contained low (less than 0.09-0.7 ng g-1) levels of trimethyl- and dimethyl lead. Triethyl lead was found at similar levels in several samples. Total lead levels were higher with values ranging from less than 5 ng g-1 to 2.9 micrograms g-1. Detection limits for the organolead and total lead methods were 0.07-0.2 and 3-19 ng Pb g-1 respectively.