An ionic liquid doped electrochemical copolymer coating of indole and 3-methylthiophene for the solid-phase microextraction of polycyclic aromatic hydrocarbons

A novel poly(indole-co-3-methylthiophene)–ionic liquid (i.e., 1-allyl-3-vinylimidazolium bis((trifluoromethyl)sulfonyl)imide) (P(In–3-MeT)/IL) composite film was electrodeposited on a stainless steel wire for headspace solid phase microextraction. The obtained P(In–3-MeT)/IL coating was rough and showed a cauliflower-shape. It had high thermal stability (up to 450 °C) and mechanical stability and could be used for at least 180 times in solid phase microextraction (SPME) without a decrease in extraction performance. The coating exhibited high extraction capacity for some polycyclic aromatic hydrocarbons (e.g. naphthalene, 1-methylnaphthalene, acenaphthene, biphenyl, fluorene and phenanthrene) due to the strong hydrophobic and π–π interactions between the analytes and P(In–3-MeT)/IL. Through coupling with GC, good linearity (correlation coefficients higher than 0.9994), wide linear ranges (0.05–50 μg L−1) and low limits of detection (6.25–25.2 ng L−1) were achieved for these analytes. The reproducibility (defined as RSD) was 3.5–5.5% and 4.5–7.2% for single fiber (n = 5) and fiber-to-fiber (n = 5), respectively. The SPME-GC method was successfully applied for the determination of three real samples, and the recoveries for standards added were 86.8–105% for mosquito-repellent incense, 89.9–110% for cigarettes and 82.3–103% for industrial lubricant.