Determination of Caprolactam Monomer and Oligomer Residues in Salvianolic Acid Extracts

Objective:To establish a method for detecting the residues of caprolactam and oligomer in the salvianolic acid extracts.Method: Acid hydrolysis of polyamide resin was optimized.Salvianolic acid extract was hydrolyzed under this optimized condition,which was further enriched and purified using SPE solid extraction column.HPLC was employed to detect caprolactam and aminocaproic acid,the hydrolyzed oligomer.Chromatographic column was AtlantisRRT3(4.6 mm×250 mm,5 μm).Mobile phase was methanol-water with step gradient elution;Column temperature was at 30 ℃.Flow rate was 0.5 mL·min-1.Detection wavelength was at 209 nm.Result: Linear relationship was good in the range of 7.012 6-0.004 5 g·L-1 with a regression coefficient of 0.999 5.Recovery of aminocaproic acid was 96.25%,RSD 1.17%.Recovery of polyamide resin was 101.27%,RSD 4.33%.Conclusion: The method is simple and accurate for determination of caprolactam and oligomer in the salvianolic acid extract.