Determination of salicylic acid using a magnetic iron oxide nanoparticle-based solid-phase extraction procedure followed by an online concentration technique through micellar electrokinetic capillary chromatography

In this study, a magnetic iron oxide nanoparticle-based solid-phase extraction procedure combined with the online concentration and separation of salicylic acid (SA) through micellar electrokinetic chromatography–UV detection (MEKC–UV) was developed. Under optimal experimental conditions, a good linearity in the range of 0.01–100 μmol L⁻¹ was obtained with a coefficient of correlation of 0.9999. The detection sensitivity of the proposed method exhibited an approximately 1026-fold improvement compared with a single MEKC method without online concentration, and the detection limit (S/N = 3) was 3.80 nmol L⁻¹. The repeatability of the method was evaluated using intraday and interday RSDs (11.5% and 17.0%, respectively). The method was used to determine SA concentrations in tobacco leaves (Nicotiana tabacum L. cv. Samsun) from the NN genotype, nn genotype, and Nt-NahG mutant strains, as well as in shampoo and ointment samples. Rapid extraction and separation ( < 50 min), acceptable repeatability (RSD < 17.0%), and high spiked recoveries (95.8%–102.4%) were observed for plants, detergents, and pharmaceuticals.