This report describes an ion chromatography method for determining thiocyanate in dairy products. Milk samples were deproteinized by adding acetonitrile followed by centrifugation, microporous filtration and chromatography on LC-C18 SPE column. The analyte was monitored by ion chromatography. The optimized mobile phase consisted of 1.7 mmol/L sodium bicarbonate, 1.8 mmol/L sodium carbonate and 10% aqueous acetone solution. The suppressor was activated and regenerated with 0.2% sulfuric acid as an inhibitor. The detection limit for thiocyanate was 2.0 mg/kg, and the standard curve exhibited a correlation coefficient above 0.99 in the linear range of 0.1–20 mg/kg (mg/L). Recovery rates for spiked samples ranged from 93% to 97%, and repeatability expressed as relative standard deviation varied between 0.8% and 1.34% (n = 5). The detection accuracy for milk powder standard was 98%. The presented method was characteristic of easy operation, accurate and repeatable results and low detection limit, and was useful for the determination of thiocyanate in dairy products.

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.

This paper is about the detection the four serotypes A, B, E and F of Clostridium botulinum from milk powder and whey powder by using real-time fluorescent quantitative PCR method (RT-PCR). The standard curves for blends of serotypes A and B as well as of E and F were established using the original positive control from a commercial RT-PCR kit and its 10, 102, 103 and 104-fold dilutions. The cycle threshold (Ct) values exhibited excellent specificity, repeatability and accuracy. By using the method, none of these four serotypes was detected in 82 samples milk power and whey power with suspected strains as confirmed by the Chinese national standard and the industry standard of entry-exit inspection and quarantine.

A method was developed for the determination of 20 phthatic acid esters in milk and dairy products by gas chromatography-mass spectrometry (GC-MS). Samples were extracted with n-hexane and separated on a DB-5MS capillary column (30 m × 0.25 mm, 0.25 μm). The injector temperature was 280 ℃,the interface temperature was 280 ℃, and the ion source temperature was 230 ℃. Under optimized conditions, the linear range was 0-10 μg/mL with a correlation coefficient greater than 0.9990. The average spike recovery rates were in the range of 80%-109%. The detection limits were respectively 1.0 and 0.5 mg/kg for DINP and DIDP and 0.05 mg/kg for 18 others. This method proved to be simple, rapid, sensitive, specific and accurate.

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.