Offline Selective Extraction Combined with Online Enrichment for Sensitive Analysis of Chondroitin Sulfate by Capillary Electrophoresis

Abstract A capillary electrophoresis (CE) method combined with online and offline enrichment for improving the detection sensitivity of chondroitin sulfate (CS) is established. The online enrichment method is based on the field-amplified sample stacking and large volume electrokinetic injection, and offline enrichment is based on the association between cetyltrimethylammonium chloride and CS. Experimental parameters affecting CE method such as the type and pH of background electrolyte, the injection mode and time and the steps of offline enrichment were optimized. Under optimum conditions, the calibration plot between CS concentration and peak area was linear in the range of 1 ~ 100 μg/mL. The enrichment factor was 130 times and the limit of detection was 50 ng/mL. The average recovery was 103.5% and the relative standard deviation of peak area was <2.0%. The method was successfully applied to the quantitative analysis of CS in drugs.