DETERMINATION OF ETHYLENETHIOUREA IN WATER BY SINGLE-STEP EXTRACTIVE DERIVATIZATION AND GAS CHROMATOGRAPHY-NEGATIVE ION CHEMICAL-IONIZATION MASS-SPECTROMETRY

A method for the determination of ethylenethiourea (ETU) in water samples is described that involves a single-step derivatization and extraction by means of phase transfer-catalysed reaction with 3,5-bis(tri-fluoromethyl)benzyl bromide followed by gas chromatography-electron-capture negative ion mass spectrometric separation and detection. The reaction resulted in three ETU derivatives, identified by CC-Fourier transform spectrometry as the mono-N-substituted form and two forms substituted at the N,N'- and the N,S-positions. Quantification in the multiple-ion detection mode was performed on the abundant [M-227](-) ions of the N,N'-isomer in low-level (<5 mu g/l) and at the N,S-isomer in high-level samples (>5 mu g/l). The limit of determination in surface water samples was 0.05 mu g/l with recoveries ranging between 60 and 110%. The method was applied for confirmation purposes for the presence of ETU as analysed by HPLC with UV detection. In general, a good correlation was found between the results from both methods.