Determination of organophosphorus pesticides in spiked river water samples using solid phase microextraction coupled to gas chromatography with EI-MS and ICP-MS detection

Solid-phase microextraction (SPME) has been developed for the gas chromatographic (GC) analysis of a wide range of organophosphorus pesticides (OPPs) in river water samples. Experimental conditions, such as type of fiber, extraction mode, extraction time, extraction temperature, salt additives and pH, were optimised. The optimized SPME procedure was evaluated by means of two different detection systems: GC-MS (using electron impact as ionization source) and GC on-line coupled to an inductively coupled plasma mass spectrometer (ICP-MS). The addition of small percentages of nitrogen in the argon carrier gas flow proved to be very suitable for sensitivity enhancement of the element specific detection by ICP-MS. The analytical figures of merit of the two systems have been compared for the detection of OPPs making use, in the case of GC-ICP-MS, of the selective monitoring of phosphorus and other heteroelements (S, Cl, Br) present in the selected pesticides. Precision, linearity range, detection limits and accuracy of the SPME-GC-ICP-MS method were evaluated and compared with those obtained by SPME-GC-MS. Detection limits ranging from 0.8 ng L-1 to 504 ng L-1 and 0.09 ng L-1 to 143 ng L-1 were obtained with SPME-GC-MS and SPME-GC-ICP-MS, respectively. Both methodologies were applied to the analysis of spiked river water samples.