A polypyrrole film with dual counter ions as a highly efficient medium for headspace solid-phase extraction of chloro-organic compounds

Abstract

A polypyrrole (PPy) film containing dodecyl sulfonate (SDS) as an organic counter ion and primary phosphate as an inorganic counter ion was electrodeposited on a stainless steel wire. The process was carried out under a constant deposition potential of 1.5 V that was applied to an aqueous solution containing pyrrole monomer, SDS and phosphate ions in varying concentrations. Films (with thicknesses 66 μm) were synthesized in the presence and absence of phosphate ions, and their surfaces were characterized by scanning electron microscopy. The surface structure of the PPy–SDS–H2PO4− film compared to films made from PPy-SDS only or PPy-phosphate only, are more porous and less smooth. The effects of counter ions and their weight ratios, of applied voltage and time for electrodeposition were optimized. The applicability of this unbreakable coating is demonstrated by headspace solid-phase micro extraction of selected chlorobenzenes from aqueous samples. Extraction temperature and time, ionic strength, desorption conditions and stirring rates were also optimized. Under optimum conditions and by a gas chromatography–mass spectrometry for separation and detection, the relative standard deviations for the determination of chlorobenzenes in distilled water spiked at a level of 30 ng L−1 were 3–8 % (for n = 3), the limits of detection are between 0.5 and 1 ng L−1, and the calibration plots cover the 2.5 to 1,000 ng L−1 range. The method was applied to the analysis of (spiked) water samples, and relative recoveries were found to range from 95 to 103 %.