Optimization of a sample preparation procedure for the speciation of organotin compounds in sediment samples using GC-AED

Results of a comprehensive study of all analytical steps involved in the sa mple preparation procedure for the speciation of butyl- and phenyltin compo unds in sediments are presented. The proposed method is based on acid leach ing (using aqueous acetic acid) and simultaneous extraction of the ionic sp ecies into an organic solvent (n-hexane/ethyl acetate) with the addition of a complexing agent (diethyl dithiocarbamic acid). After evaporation to dry ness, the residue is derivatized with sodium tetraethylborate in an aqueous buffer solution (acetate buffer, 0.1 M, pH 5) and extracted into n-hexane. Cleanup is performed over basic alumina and the ethylated organotin specie s are analyzed with a gas chromatograph coupled to a microwave-induced heli um plasma atomic emission detector (GC-AED). The optimized method was valid ated within an interlaboratory study for the certification of tributyltin, triphenyltin and their degradation products in a freshwater sediment, the B CR candidate reference material. 646.