Layer-by-layer fabrication of g-C₃N₄ coating for headspace solid-phase microextraction of food additives followed by gas chromatography-flame ionization detection

This work demonstrates a simple layer-by-layer approach for producing graphitic carbon nitride (g-C₃N₄) coated fibers for solid-phase microextraction (SPME) with sol-SiO₂ as the binder. With the prepared g-C₃N₄ coated SPME fiber, a headspace SPME coupled with GC (HS-SPME-GC) method was developed for the analysis of food additives. Detection limits of 0.2-4.0 ng mL^-1 were obtained for the analysis of five food additives including methyl cinnamate, ethyl cinnamate, benzyl cinnamate, isobutyl cinnamate, and butylated hydroxytoluene by the developed HS-SPME-GC method with flame ionization detection. The method exhibited good linearity in the range of 0.5-1000.0 ng mL^-1 with the coefficient of determination (R²) not lower than 0.9930. The repeatability of the prepared coating was 2.2-5.4% (n = 3) for the same fiber, and the reproducibility was in the range of 5.3-12.4% for three different fibers. The recovery of the developed method was in the range of 73.3-109.8%. Based on the as-prepared g-C₃N₄ coating, the developed HS-SPME-GC method was successfully applied to the analysis of real samples including biscuits and milk tea beverages.