Polypyrrole/sol-gel composite as a solid-phase microextraction fiber coating for the determination of organophosphorus pesticides in water and vegetable samples

A novel solid-phase microextraction (SPME) fiber coated with polypyrrole/sol-gel composite was prepared through electrochemical deposition. The composite polymer coating was prepared using a three-electrode electrochemical system and directly deposited on a stainless steel wire by applying a constant potential (1.2 V for 1000 s). The coating has porous surface structure, stable performance in high temperature, and good coating preparation reproducibility. The SPME composite coating was evaluated by analyzing some organophosphorus pesticides (OPPs) in water and vegetable samples followed by gas chromatography and nitrogen phosphorus detection. Different SPME parameters influencing the extraction efficiency such as coating thickness, salt concentration, stirring rate, extraction time and temperature, desorption time and desorption temperature were investigated. Under the optimized conditions, the coating showed better extraction efficiency than polypyrrole and commercial SPME fibers. The detection limits were 1.5-10 ng L-1. Relative standard deviations for intra- and inter-day precision for a single fiber were in the range of 1.1-2.9% and 2.2-4.2%, respectively. Fiber to fiber reproducibility was in the range of 6.0-10.1% (n=3). The calibration curves were linear in the concentration range from 5 to 2000 ng L-1 (r(2) > 0.9953). Finally, the developed method was applied for the analysis of cucumber, lettuce, tap and well water samples and the relative recovery was found to be in the range of 80-109%, at the optimum conditions. (C) 2013 Elsevier B.V. All rights reserved.