Determination of 4 Kinds of Frequently-used Spices in Dairy Products by High Performance Liquid Chromatography-Tandem Mass Spectrometry

An analytical method based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed for detecting 4 kinds of frequently-used spices (maltol, ethyl-maltol, vanillin and ethyl-vanillin) in dairy products. The samples were extracted by water and tert butyl methyl ether, the supernatants were extracted by 0.2 mol/L sodium hydroxide solution alkali solution (the volume ratio of alkali solution to MTBE was 1:5) for purification and enrichment of target composes to the aqueous phase. The separation of these 4 compounds was carried out by a HSS T3 column and the mobile phase performed on 0.05% formic acid aqueous solution-methanol by gradient elution, electrospray ionization source (ESI) was applied and operated in the positive mode. Multiple reaction monitoring (MRM) mode was used to monitor ions. The results showed that the method had a good linearity range between 2.0~100.0 ng/mL (R²>0.995) and the detection limits were as low as 8.0 μg/kg. The matrix effects of 4 kinds of spices in different dairy products showed week matrix suppression effects and ranged from 80%~100%, suggesting the matrix effects advisably being ignored in routine testing. The average recoveries of the targeted compounds range from 67.7% to 104.8% at spiked levels of 10, 25 and 100 μg /kg, and relative standard deviations range from 2.5% to 11.9% (n=6). The method is simple, sensitive, accurate and reliable.