Development of a fiber coating based on molecular sol–gel imprinting technology for selective solid-phase micro extraction of caffeine from human serum and determination by gas chromatography/mass spectrometry Original Research Article

In this work, a molecular sol–gel imprinting approach has been introduced to produce a fiber coating for selective direct immersion solid-phase microextraction (SPME) of caffeine. The polymerization mixture was composed of vinyl trimethoxysilane and methacrylic acid as vinyl sol–gel precursor and functional monomer, respectively. Caffeine was used as template molecule during polymerization process. The prepared fibers could be coupled directly to gas chromatography/mass spectrometry (GC/MS) and used for trace analysis of caffeine in a complex sample such as human serum. The parameters influencing SPME such as time, temperature and stirring speed were optimized. The prepared coating showed good selectivity towards caffeine in the presence of some structurally related compounds. Also, it offered high imprinting capability in comparison to bare fiber and non-imprinted coating. Linear range for caffeine detection was 1–80 μg mL−1 and the limit of detection was 0.1 μg mL−1. The intra-day and inter-day precisions of the peak areas for five replicates were 10 and 16%, respectively.