Simultaneous determination of loading capacity and selectivity in preparative off-line two-dimensional separation: An application for purification of corilagin from Pomegranate flower extracts.

This work describes the development of capacity orthogonal chromatography (COC), a new technique for simultaneously determining the loading capacity and orthogonality during the construction of two-dimensional (2D) separations. Three steps were required for the construction of a COC based on the correlation between the selectivity factor (α) and both orthogonality and loading capacity. (1) α values of the impurities-target compound were used to normalize the retention of the impurities around the target compound. (2) α values were input into four quadrants of a coordinate system to identify correlations between orthogonality and loading capacity. α values of the impurities must be greater in the first dimension than the second dimension, with iterated analyses performed until an αmax is obtained for the two purification methods. (3) Touch-peak separation using the first-dimensional αmax was performed and the target compound was collected. The co-eluted impurities are further separated in the second dimension. To test the efficiency of this technique, a COC using two methods on a standard C18 column was developed to purify corilagin from pomegranate flower extract. Despite its low abundance, 288 mg of corilagin was obtained by COC and further purified by LH-20 gel chromatography to obtain the compound with an 80.0% recovery and 98.4% purity. Compared to COC, the purity of corilagin independently obtained using the same purification methods and identical loading capacity was poor (60.1% and 61.6%). These results indicate that COC is a useful tool for extending loading capacity in the development of preparative 2D separations.