A method for determining vitamin C (VC) in dairy products by high performance liquid chromatography (HPLC) is described. Samples were added with metaphosphoric acid to precipitate proteins, filtered through filter paper, separated on a C18 chromatographic column with 0.25% metaphosphoric acid solution as mobile phase, detected with a UV detector, and quantified by an external standard method. The method proved simple and rapid with good accuracy and precision. The recovery of VC ranged between 93.6 % and 103.9% with relative standard deviation of 2.56% to 4.05%. The detection limit was 1 mg/kg.

A method for determining parabens and natamycin in dairy products by HPLC is described. Samples were extracted with methanol and separated on a C18 column with methanol-acetic acid solution as mobile phase. UV detection was performed at 256 nm and 305 nm. Complete separation of pimaricin and four parabens, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate and butyl 4-hydroxybenzoate was achieved within 35 min. Under optimized conditions, the linear ranges for the food antiseptics was 1–100 mg/kg with a correlation coefficient greater than 0.9990, and their average recovery rates from blank real samples spiked at three different levels was between 83.7% and 103%. This method was simple, rapid and accurate.