A high-throughput method for the screening and quantitation of 54 pesticide residues in fresh milk was developed by quick, easy, cheap, effective, rugged, safe (QuEChERS) extraction followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The study optimized the composition of mobile phase, extraction solvent, extraction solvent volume, extraction salt packet formulation, and purification packet formulation. Furthermore, the matrix effect was evaluated and methodological evaluation were carried out. The results showed that the linear range was 5.0–100.0 μg/L for all 54 pesticides, with correlation coefficients (r) higher than 0.999. The limit of quantification (LOQ) was 10.0 μg/kg for all target analytes, and the average recoveries from spiked samples were 67.78%–119.38%, with relative standard deviations (RSDs) (n = 6) lower than 9%. The method is simple, rapid, sensitive, and accurate. It can meet the requirements of the simultaneous detection and analysis of 54 pesticide residues in fresh milk.

Lactulose, also known as isomerized lactose, is a reducing disaccharide made from the dairy industry by-product lactose. Its concentrate is an important over-the-counter (OTC) drug that has a significant therapeutic effect on acute or chronic constipation and hepatic encephalopathy. The methods that have been developed to produce lactulose include the chemical method, β-galactosidase method and epimerase method. In recent years, the epimerase method has aroused extensive attention due to the high conversion rate it yields, which makes it a promising candidate for lactulose preparation although currently there exist some bottlenecks like the high proportion of epilactose as a by-product and the rather low enzyme activity. This article reviews the history and current status of research on the methods for lactulose production, in the hope of providing reference for basic theoretical research and industrialization in this field.