A stop-flow two-dimensional liquid chromatography method for determination of food additives in yogurt
A heart-cutting, two-dimensional (2D) high performance liquid chromatography method was developed in this research to simultaneously quantify five food additives (aspartame, benzoic acid, natamycin, saccharin sodium and sorbic acid) in yogurt drinks. In this 2D system, a Venusil XBP-C4 column was selected in the first dimension as a pre-separation column; a Purospher® STAR RP-18 column was employed in the second dimension as a further analysis column; a two position, six-port switching valve was used to transfer the targets from the first dimension to the second dimension under stop-flow conditions. To investigate the specificity and accuracy of the new system, it was validated in terms of selectivity, response function, linearity, precision, sensitivity and recovery. In addition, a conventional single-dimensional high performance liquid chromatography method was also proposed for comparison. The recovery of food additives obtained with the new method (from 94.5% to 103.9%) was significantly better than that obtained with the conventional method (from 75.1% to 110.4%). Furthermore, this new method benefits from a simplified one-step sample preparation procedure, which contributes to a shorter analysis time, more accurate results and less solvent usage.