INTERFERENCES GENERATED BY ORGANIC AND INORGANIC-COMPOUNDS DURING ORGANOTIN SPECIATION USING HYDRIDE GENERATION COUPLED WITH CRYOGENIC TRAPPING, GAS-CHROMATOGRAPHIC SEPARATION AND DETECTION BY ATOMIC-ABSORPTION SPECTROMETRY

Hydride generation reactions are frequently used for the speciation an alysis of organotin compounds in a wide variety of matrices. However, the organotin determination procedure may be altered by different inte rferences mechanisms. This work evaluates the interferences likely to occur in the determination of tributyltin in a harbour sediment candid ate reference material for the EEC Community Bureau of Reference with the method of hydride generation combined on-line with cryogenic trapp ing, gas chromatographic separation and detection by atomic absorption spectrometry. First, a full geochemical characterization of the sedim ent and of its acetic acid leachate was achieved to evaluate interferi ng compounds that may inhibit the determination of TBT by hydride gene ration in this sediment. Second, interference studies on various organ ic and inorganic compounds likely to alter the overall organotin deter mination were carried out with simple model solutions. These model sol utions were spiked successively with different possible interfering co mpounds mixed with the organotins under study, i.e., monomethyltin (MM T), monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in a mi xed solution at concentrations of 5 ng as Sn of each compound in 50 ml of water. Organic interferents studied were organic pollutants (organ ic solvents, polychlorinated biphenyls, pesticides, n-alkanes), humic substances and a complexing agent, EDTA. The inorganic interferents we re represented by a mixture of fourteen inorganic metals. The addition of organic compounds to the hydride generation reaction had little ef fect on the signal suppression for all organotin species. Reproducibil ity wassignificantly affected only by the presence of humic substances in solution. Signal suppression was observed only for the monoalkylti ns (MMT and MBT) in the presence of EDTA. Solutions of mixed inorganic metals were found to be highly efficient in inducing severe signal su ppression for all organotin compounds at a level of 100 mu g of each e lement. Interference mechanisms during the speciation determination st ep are outlined and discussed.