DETERMINATION OF BUTYLTIN COMPOUNDS IN SEDIMENTS BY GC MS AFTER THEIRCONVERSION TO METHYL-DERIVATIVES/

A selective and rapid procedure was developed for the determination of trace amounts of butyltin compounds in sediments by capillary gas chr omatography with mass spectrometric detection. Analytes were isolated from the sediment samples by extraction with a methanolic solution of HCl (0.5 mol l(-1)) followed by reextraction into a hexane solution of tropolone (0.1%). The organotin compounds were converted to the nonpo lar methyl derivatives by methylation with a Grignard reagent. The rec overy was determined for each step of the procedure. This efficient se paration method combined with the ion trap based mass detection ensure s a high selectivity even for concentrations approaching the detection limit (0.15 pg for Bu3SnMe) in real sediments. Chemical ionization us ing acetonitrile as the reaction gas, exhibiting a similar sensitivity of determination and reducing the background level, can serve as a co nvenient alternative of detection for sediments heavily contaminated b y organics. The method was applied to a set of real samples and valida ted by analysis of a certified reference material.