Preparation of chitosan‐modified silica nanoparticles and their applications in the separation of auxins by capillary electrophoresis

In recent years, nanoparticles have gained more attention when used in separation science. In this study, chitosan‐modified silica nanoparticles were successfully synthesized and characterized by transmission electron microscopy, elemental analysis and zeta potential measurements, etc. When added into the running buffer solution as pseudo‐stationary phase in capillary electrophoresis, the separation of four representative auxins, i.e., indole‐3‐acetic acid, indole butyric acid, 2,4‐dichlorophenoxyacetic acid, 1‐naphthaleneacetic acid, was carried out. Some important factors, such as the nanoparticles concentration, the pH and concentration of the running buffer solution, were also investigated on the separation. Under optimized experimental conditions, all the auxins investigated can be baseline separated within 5 min with higher column performance. The method established can also be used for quantitative analysis. The relative standard deviations obtained for indole‐3‐acetic acid, indole butyric acid, 2,4‐dichlorophenoxyacetic acid, 1‐naphthaleneacetic acid were in the range of 1.6–5.7% for peak area and 0.53–1.60% for migration time. The calibration curves obtained from the peaks areas for auxins were linear in the range of 0.1–80 mg/L with the correlation coefficients of 0.994–0.999. The limit of detection (S/N = 3) was 11–75 μg/L. The developed method was also successfully used for the determination of auxins in fruits and vegetables samples with good recoveries.