Solid-phase microextraction of phthalate esters from aqueous media by electrochemically deposited carbon nanotube/polypyrrole composite on a stainless steel fiber

A novel direct immersion solid-phase microextraction (DI-SPME) method using a stainless steel wire electrochemically coated with oxidized multiwalled carbon nanotubes–polypyrrole composite (MWCNTs–PPy) was used in the gas chromatographic (GC) determination of phthalate esters in aqueous samples. The composite coating did not swell in organic solvents nor did it strip off from the substrate. It was also highly stable and extremely adherent to the surface of the steel fiber. 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 studied. Under optimized conditions, the detection limits for the phthalate esters varied between 0.05 and 0.1 ng mL−1, the inter-day and intra-day relative standard deviations for various phthalates at 1.0 ng mL−1 concentration level (N = 7) using a single fiber were 6.2–10.2% and 7.7–10.5, respectively. The fiber-to fiber RSD% (N = 3) was 9.3–12.1% at 10 ng mL−1. The linear ranges varied between 0.5 and 300 ng mL−1. The method was successfully applied to the analysis of mineral water samples with the recoveries from 90 to 113%.