Electrochemical preparation of polyaniline–polypyrrole solid-phase microextraction coating and its application in the GC determination of several esters

A novel polyaniline–polypyrrole (PANI–PPY) composite film coated stainless steel wire was prepared by cyclic voltammetry. Firstly, PANI was electrodeposited on a stainless steel wire from a solution containing 0.1 M aniline and 1 M HNO3, after the PANI coating was dried in air PPY was electrodeposited on it from a solution containing 0.1 M pyrrole and 0.1 M p-methylbenzene sulfonic acid. The resulting PANI–PPY fiber showed reticulate structure and had large specific surface area. When it was used for the headspace solid-phase microextraction of several esters (i.e. methyl anthranilate, ethyl-o-aminobenzoate, dimethyl phthalate, methyl laurate, and diethyl phthalate), followed by gas chromatographic determination, it presented higher extraction capability in comparison with PPY and PANI coatings. Under the optimized conditions, the linear ranges were 0.07−300 μg L−1 and the detection limits were 0.05−0.38 μg L−1 for different esters. The PANI–PPY fiber also showed high durability, after being used for about 160 times its extraction capacity only changed a little. The proposed method was successfully applied to the determination of these esters in real samples and the recoveries were 90–102%.