Dispersive liquid-liquid microextraction applied to the simultaneous derivatization and concentration of triclosan and methyltriclosan in water samples

Abstract

A fast and novel sample preparation procedure for the determination of triclosan (TCS) and methyltriclosan (MTCS) in water samples is presented. Dispersive liquid-liquid microextraction, using a ternary mixture consisting of a disperser, an extractant and N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) as derivatization reagent, was used for the simultaneous derivatization, case of TCS, and concentration of both species in different water samples. Analytes were determined by gas chromatography with tandem mass spectrometry (GC-MS/MS). Influence of different factors on the performance of the sample preparation process is thoroughly discussed. Under final working conditions, a mixture of 1 mL of methanol, 40 L of 1,1,1-trichloroethane and the same volume of MTBSTFA was added to 10 mL of water in a conical bottom glass tube. After centrifugation, the settled phase was injected directly in the chromatographic system. TCS was quantitatively extracted and converted into the corresponding tert-butyldimethylsilyl derivative, whereas for MTCS an extraction yield around 90% was attained. Limits of quantification between 2 and 5 ng L-1 and reproducibility values below 10% were achieved; moreover, the performance of the extraction process was scarcely affected by the type of water sample. Globally, these values are comparable, or even better, to those reported for other approaches applied to the determination of same compounds, with the advantage of a shorter sample preparation step. Analysis of surface and wastewater samples confirmed the ubiquitous presence of TCS in the aquatic environment at levels from 20 to 700 ng L-1.