Determination of bovine lactoferrin in infant formula by capillary electrophoresis with ultraviolet detection

A new and simple method for the quantitative determination of bovine lactoferrin (Lf) in infant formula by capillary electrophoresis with ultraviolet (CE-UV) detection was established. Effective sample pre-treatment and the addition of buffer additive to the running buffer played key roles in the accurate assay of the Lf in infant formula. In the method, the infant formula samples were pretreated with 50 mmol/L acetic acid without pH adjustment, which is beneficial for high sample throughput. The separation was carried out in an uncoated capillary with 50 μm i.d. and total length of 27 cm (20 cm to the detector). The running buffer consisted of 40 mmol/L NaH₂PO₄, 40 mmol/L H₃PO₄ and 5 mmol/L polyethylene glycol dodecylether (Brij 35). The addition of the non-ionic surfactant Brij 35 to the running buffer served to suppress the Lf adsorption to the capillary wall, and also allowed for high-efficiency separation of Lf from adjacent unknown proteins. The intra- and inter-day precision of the method were 2.4% and 4.6% (n=7), respectively. The corrected peak area (A(c)) and the concentration of Lf showed a strong linear relationship within the range of 10-400 mg/L with a linear correlation coefficient (r) of 0.9999. The limit of detection (LOD) and limit of quantitation (LOQ) were 3mg/L (S/N=3) and 10mg/L (S/N=10), respectively. The method was successfully used to quantitate the Lf in infant formula with satisfactory results.