Poly (2-methyl-2-oxazoline) coating by thermally induced immobilization for determination of bovine lactoferrin in infant formula with capillary electrophoresis

In this work, a one-step coating procedure by a simple annealing protocol of poly (2-methyl-2-oxazoline)-random-glycidyl methacrylate (PMOXA-r-GMA) copolymer was used to yield covalent and cross-linked PMOXA-based antifouling coating on a fused-silica capillary inner surface, which was used to determine the bovine lactoferrin (Lf) in infant formula by capillary electrophoresis with ultraviolet (CE-UV) detection. The Xray photoelectron spectroscopy (XPS) confirmed that PMOXA-r-GMA could be bonded onto fused-silica capillary inner wall and stable electroosmotic flow (EOF) was obtained in the PMOXA-r-GMA coated capillary at pH 2.2-9.0. The separation of a mixture of four basic proteins indicated that the PMOXA-r-GMA coated capillary exhibited excellent separation efficiency for the basic proteins. Therefore, the PMOXA-r-GMA coated capillary was used to determine the quantity of Lf in infant formula. Under the optimal conditions, the peak area (A) and the concentration of Lf showed a good linear relationship within the range of 10-500 g/mL with a linear correlation coefficient of 0.9995. The limit of detection (LOD) and limit of quantitation (LOQ) for Lf were 5.0 g/mL and 16.7 g/mL, respectively. The recoveries at spiked concentrations of 0.20 and 0.40 mg/mL Lf in infant formula were 97.1 +/- 5.5% - 97.8 +/- 5.1%. The determined values of Lf in infant formula samples with Lf were consistent with the nominal values, indicating that our CE method could be successfully applied to the quantitative analysis of Lf in commercial infant formula.