Polyphosphate-doped polypyrrole coated on steel fiber for the solid-phase microextraction of organochlorine pesticides in water

A solid-phase microextraction technique using steel fiber coated with 20 mu m polypyrrole (Ppy) doped with polyphosphate was developed for the CC determination of a group of organochlorine pesticides (OCRs) in water. The coating was prepared using a three-electrode electrochemical system from a 10% aqueous sodium polyphosphate solution containing 0.05 M pyrrole by applying a constant potential of 1.2V for 30 min. In order to obtain an adherent, smooth and stable film of polypyrrole, experimental parameters related to the coating process consisting of the type of dopant or counter-ion, deposition potential, concentration of the monomer, concentration of the counter-ion, and deposition time were optimized. The effects of various parameters on the efficiency of SPME process such as extraction time, extraction temperature. ionic strength, desorption time, and desorption temperature were also studied. The coating was highly stable and extremely adherent to the surface of the steel fiber. The method was linear for at least three orders of magnitude with correlation coefficients varying from 0.9818 to 0.9977. The accuracies found through spiking blank samples showed high recoveries between 82 and 110%. Intra- and inter-day precisions of the method were determined from mixed aqueous solutions containing 1.0 ng ml(-1) of each OCR The intra-day precisions varied from 4.7% for heptachlor to 11.4% for methoxychlor, while the inter-day precisions varied from 6.8% for endosulfan 1 to 13.0% for p,p'-DDD and o,p-DDD. Limits of detection based on S/N = 3 were in the range 0.015-0.66 pg ml(-1). The proposed method was applied to monitor organochlorine pesticides in some well water samples. (C) 2009 Elsevier B.V. All rights reserved.