Analysis of Additives in Milk Powders with SPE-HPLC or 2D-HPLC Method

Abstract

Dairy products are beneficial to human health, especially for formula-fed newborns. According to the regulation of FDA and China national food safety standard, food additives such as benzoic acid, sorbic acid, natamycin, lysozyme, saccharin sodium, and aspartame are not permitted to be added to milk powder. So, the establishment of accurate and convenient methods for the analysis of these food additives in milk powder is critical to people's health. For the reason of the complex matrix of infant milk powders, we compared six sample pretreatment methods (liquid-liquid extraction, organic precipitation, heavy precipitation, and three different solid-phase extraction (SPE) methods (C18, HLB, MAX)) from recovery, easy operation, time cost, and organic solvent usage aspects. Finally, Poly-Sery HLB cartridge was confirmed as the most appropriate material for its high recovery and time cost merits. We are also introducing two-dimensional liquid chromatography (2DLC) method for the simultaneous determination of five major proteins and seven food additives in milk powders. Optimization of switching mode, choice of columns, mobile phase, and flow speed was discussed. We also compared limit of detection (LOD), recovery, and sample treatment with the results of high-performance liquid chromatography (HPLC). Results show that 2DLC is simpler, faster, and more accurate than the HPLC method.