Oxidized Multi-Walled Carbon Nanotubes as SPE Sorbent for Determination of Mefenacet and Its Degradation Products Residues in Water Samples by RRLC-UV-ESI-MS

A new method was developed for the analysis of herbicide mefenacet (MN) and its three photolysis degradation products namely hydroxylbenzothiazole (HBT), N-methylaniline (N-MA) and 2-benzothiazoloxyacetic acid (2-BAA) in water samples by rapid resolution liquid chromatography coupled with UV detection and electrospray ionization mass spectrometry. In the SPE pre-concentration step, the adsorptive potential of oxidized multi-walled carbon nanotubes for the extraction of these four target analytes was investigated for the first time. Parameters influencing the extraction efficiency, such as sample flow-rate, eluent volume and sample volume, were examined. The mean recoveries were between 85.6 and 101.4% and relative standard deviations were between 3.0 and 9.2%. The limits of detection obtained were 0.02 mu g L-1 for MN and 2-BAA and 0.04 mu g L-1 for HBT and N-MA. The proposed method was applied to monitor the residual concentrations of these four target analytes in 39 real water samples collected from April to July of 2009.