A simple, low cost GC/MS method for the sub-nanogram per litre measurement of organotins in coastal water

Tributyltin (TBT) is a legacy pollutant in the aquatic environment, predominantly from its use in anti-foulant paints and is listed as a priority hazardous substance in the European Union’s Water Framework Directive (WFD). Measuring low concentrations of TBT and other organotins (e.g. monobutyltin (MBT), dibutyltin (DBT), diphenyltin (DPhT) and triphenyltin (TPhT)) at sub ng/L concentrations in coastal waters using standard laboratory instrumentation is very challenging. Conventional, low injection volume gas chromatography/mass spectrometry (GC/MS) combined with liquid-liquid extraction typically achieves limits of detection for TBT ∼10 ng L−1. We describe a simple, programmed temperature vaporisation-large injection volume (50 μL), GC/MS selected ion monitoring method for measuring DBT, TBT, DPhT and TPhT in coastal waters at lower concentrations. Quantification of MBT was not possible using these injection volumes but was achieved using a 10 μL injection volume together with a reduced injection speed.This new approach offers:
• When using a 50 μL injection, limits of detection = 0.70 ng L−1 and limits of quantification = 2.1 ng L−1 for TBT were achieved in derivatised standards.
• Recoveries of TBT and TPhT from coastal water >97%.
• Time consuming, off-line sample pre-concentration methods are unnecessary.

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