Simultaneous quantification of five proteins and seven additives in dairy products with a heart-cutting two-dimensional liquid chromatography method

A heart-cutting two-dimensional high-performance liquid chromatography method was developed to simultaneously quantify five major proteins and seven food additives (maltol, ethyl maltol, vanillin, ethyl vanillin, benzoic acid, sorbic acid, and saccharin sodium) in milk and milk powders. In this two-dimensional system, a Venusil XBP-C4 column was selected in the first dimension for protein separation, and a Hypersil ODS-2 C18 column was employed in the second dimension for additive separation; a two-position, six-port switching valve was used to transfer the targets (additives) from the first dimension to the second dimension. Method validation consisted of selectivity, response function, linearity, precision, sensitivity, and recovery. In addition, a conventional one-dimensional high-performance liquid chromatography method was also tested for comparison. The two-dimensional method resulted in significantly improved recovery of the food additives compared to the conventional method (90.6-105.4% and 65.5-86.5%, respectively). Furthermore, this novel method has a simple one-step sample preparation procedure, which shortens the analysis time, resulting in more efficient analysis and less solvent usage.