Determination of butyltin species in sewage and sludge by gas chromatography-atomic absorption spectrometry.

A method for the extraction and determination of butyltin compounds in sewage and sludge is reported. Sewage and sludge samples are acidified and shaken for 2 h. The various butyltin species are extracted quantitatively by tropolone (cycloheptatrienone) in toluene, followed by ethylation to their tetraalkyl-substituted forms, BuSnEt3, Bu2SnEt2, Bu3SnEt and Et4Sn, all of which can be separated and determined by a gas chromatographic-atomic absorption spectrometric technique. The non-pesticidal octyltin species and acid-leachable SnIV species can also be determined by this method. Detection limits expressed as Sn are 40 ng dm-3 and 2 ng g-1 dry mass for sewage and sludge, respectively. Analyses of some samples from Canadian treatment plants are given.