Purification of d-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) by a temperature-modulated silica gel column chromatography: Use of Taguchi method to optimize purification conditions

The demand for high purity d-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) is increasing with the exploitation of TPGS-related products. Previously, we synthesized a TPGS mixture by esterifying vitamin E succinate with polyethyleneglycol 1000. In this study, a temperature-modulated silica gel chromatographic column was used to purify the synthesized TPGS. Taguchi method was used to optimize purification conditions associated with column temperature, loading amount, feedstock concentration and flow rate of mobile phases. Purification efficacy under the Taguchi optimized conditions was predicted theoretically and the predicted results were verified experimentally. High-performance liquid chromatography was used to quantify the unpurified and purified TPGS. The Taguchi-based analysis separately produced an optimum combination of purification conditions for TPGS purity and recovery. Under the optimized conditions, both the theoretical prediction and the confirmatory experiment yielded TPGS purity and recovery approximating to 98% each. Impressively, the study also found that column temperature had a considerable effect on purification efficacy, in particular on TPGS purity, although it was a less influential factor compared to loading amount and feedstock concentration.