Preparation of polypyrrole composite solid-phase microextraction fiber coatings by sol–gel technique for the trace analysis of polar biological volatile organic compounds

Two novel polypyrrole (PPy) composite solid-phase microextraction (SPME) fiber coatings involving polypyrrole β-naphthalenesulfonic acid (PPy/β-NSA) and polypyrrole graphene (PPy/GR) composite SPME fiber coatings were prepared by a simple sol–gel technique for selectively sampling relatively polar biological volatile organic compounds (VOCs). Crucial preparation conditions of the PPy composite SPME fiber coatings were optimized and are discussed in detail. Physical tests suggested that the PPy composite SPME fiber coatings possessed a porous surface morphology, stable chemical and thermal properties. Due to the inducing polar functional groups in the PPy molecule, the PPy composite SPME fiber coatings achieved a higher extraction capacity and special selectivity for the polar biological VOCs with conjugate structures, compared with commercial SPME fiber coatings. Enrichment factors of most of the VOCs by the PPy/β-NSA and PPy/GR SPME fibers were much higher than those achieved by common commercially available SPME fiber coatings. Finally, the PPy/β-NSA and PPy/GR SPME fiber coatings were applied for the trace analysis of typical polar VOCs from ant and coriander samples coupled with gas chromatography/mass spectrometry (GC/MS) detection, respectively. It was satisfactory that the average contents of 4-heptanone, 4-heptanol, 4-nonanone and methyl 5-methylsalicylate from ant samples were actually found to be 28.0, 58.7, 3.0 and 0.6 μg g−1, and the average contents of nonane, decanal, undecanal and dodecanal from coriander samples were actually found to be 0.79, 0.13, 0.06 and 0.21 μg g−1. The results suggested that PPy composite SPME coatings will be a potentially excellent sampling technique for the trace analysis of polar biological VOCs.