In this paper, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed to determine the contents of α-lactalbumin, β-lactoglobulin and lactoferrin in milk and infant formula. The sample was dissolved with ultrapure water, and reacted with dithiothreitol and iodoacetamide to open disulfide bonds and simultaneously protect sulfhydryl groups before being hydrolyzed with trypsin. After completion of the reaction, aqueous acetonitrile was used for making up to a constant volume, and then centrifugation was carried out to take the supernatant for quantification by external standard method. The results showed that the calibration curves for all analytes were linear in the range of 0–100 μg/mL, with correlation coefficient (r) greater than 0.995. The average recoveries of the analytes from spiked raw milk were 93.5%–117.1%, with relative standard deviation (RSD) ranging from 1.4% to 6.7%. In conclusion, the method was simple, rapid and sensitive, and could be used for the determination of α-lactalbumin, β-lactoglobulin and lactoferrin in milk and milk powder samples.

This study established a method for the simultaneous detection of 19 β-agonist veterinary drug residues in milk samples. The samples were extracted with acidified acetonitrile solution, and the phospholipids were removed by using an Oasis PRiME HLB solid-phase extraction cartridge. The analytes were detected by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Under optimized pretreatment and instrumental conditions, all analytes showed a good linear relationship in the concentration range of 0 to 10 ng/mL (R2 ≥ 0.995). The average recovery rates for milk samples spiked at levels of 0.2 to 1.0 μg/kg were between 70% and 110%, and the precision relative standard deviation (RSD) was less than 15%. The method had the advantages of simple and fast pretreatment, and high sensitivity and stability, and therefore could be used for the rapid detection of β-agonist veterinary drug residues in milk.

This paper describes a method for determination of vitamin K2 (menaquinone-7, MK-7) in milk powder using high performance liquid chromatography (HPLC). The sample was hydrolyzed with lipase (250 mg/g) for 2 h, saponified with potassium carbonate (500 mg/g), extracted with n-hexane, concentrated by rotary evaporation, reconstituted with methanol/isopropanol (4:1), and post-derivatized with C18 column and reduced column before being analyzed by HPLC with a fluorescence detector. The analyte was quantified by external standard method. The results showed that the peak of MK-7 appeared at about 19.47 min, and the calibration curve for it showed a good linear relationship in the range of 0.0–1.5 μg/mL (R2 = 0.999 95). The recoveries for blank samples spiked at 5, 10 and 25 μg/100 g were between 87.9% and 94.3%, with relative standard deviations of 0.9%–6.4%. When 2 g of sample was taken and the volume was made up to 1 mL, the detection limit was 0.15 μg/100 g and the quantification limit was 0.5 μg/100 g. The method was simple with high accuracy, sensitivity and stability, and could be used for the detection of vitamin K2 (MK-7) content in milk powder.