TRACE ANALYSIS OF TRIBUTYLTIN AND TRIPHENYLTIN COMPOUNDS IN SEA-WATERBY GAS CHROMATOGRAPHY-NEGATIVE ION CHEMICAL-IONIZATION MASS-SPECTROMETRY

An analytical gas chromatography-mass spectrometry (GC-MS) method usin g negative ion chemical ionization (NICI) has been investigated for th e determination of trace tributyltin (TBT) and triphenyltin (TPhT) com pounds in sea water. TBT and TFhT were extracted from samples as chlor ide under;he acidic condition of HCl. Doping of the GC system with a d ilute HBr-methanolic solution resulted in direct detection of the chlo rides of TBT, TPhT and tripentyltin (TPenT, internal standard). As the result of HBr doping, a sharp peal, of the respective organotin bromi des appeared: during GC analysis, halogen exchange from the chloride t o the bromide occurred. NICI-MS was highly selective and sensitive for the detection of TBT, TPhT and TPenT bromides. In the selected ion mo nitoring mode of NICI-MS, the minimum detectable amounts defined as th e signal equal to three times the standard deviation (3 sigma) of the baseline noise were 20 and 25 pg ml(-1) for TBT and TPhT, respectively . These amounts are approximately 250-400 rimes better than those in e lectron impact mode. The combination of GC using an apolar capillary c olumn doped with a dilute HBr-methanolic solution and NICI-MS made it possible to determine TBT and TPhT at less than the ng l(-1) level in sea water. (C) 1998 Elsevier Science B.V.