Optimization of the separation of beta-agonists by capillary electrophoresis on untreated and C18 bonded silica capillaries

Chemometric optimization of cation-selective exhaustive injection sweeping micellar electrokinetic chromatography for quantification of ractopamine in porcine meat

An online stacking capillary electrophoresis (CE) method, cation-selective exhaustive injection sweeping micellar electrokinetic chromatography (CSEI-sweep-MEKC), is developed and optimized for analysis of ractopamine (RP) and its homologue dehydroxyractopamine (DRP) in porcine meat. Chemometric experimental design was used to achieve the best possible optimization and reduce the number of trials and errors. The CSEI-sweep-MEKC method enables nanogram per gram level analysis, with limits of detection (LODs) in meat of 5 ng/g for RP and 3 ng/g for DRP (S/N = 3). A higher conductivity buffer (HCB) zone was injected into the capillary, allowing for the analytes to be electrokinetically injected at a voltage of 9 kV for 12 min. Using 125 mM sodium dodecyl sulfate and 15% methanol in the sweeping buffer, RP and DRP were well-separated. The method was validated with a linear calibration curve of 10-300 ng/g (r > 0.994). In comparison to the normal capillary zone electrophoresis method (1 psi for 10 s), this stacking strategy resulted in 900 times sensitivity enhancement. This technique was further applied for analyzing seven kinds of commercial meats, and the residual RP was detected in one (5.76 ng/g of RP). The data were corresponding to the data analyzed by the commercial testing kit and mass spectrometry spectra. This method was successfully used on real samples and is considered feasible for serving as a tool for routine examination in markets.