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.