Capillary Electrophoretic Separation and Quantitation of Ractopamine Stereoisomers Using Cyclodextrins as Chiral Additives

Abstract

Separation of four stereoisomers of ractopamine was conducted by capillary electrophoresis (CE) using a variety of neutral and charged cyclodextrins (CDs) as chiral selectors added into the running buffer. Among the CDs used in the screening study, only two CDs, sulfated α‐CD (S‐α‐CD) and heptakis‐(2,3‐diacetyl‐6‐sulfato)‐β‐CD (HDAS‐β‐CD), gave the baseline separation of each isomer. The separation conditions such as running buffer pH, concentration of the CD, and separation voltage were further optimized using S‐α‐CD, which provided the favorable migration order for quantitative studies. The method was validated and applied to the determination of the trace amounts of the less bioactive isomers (SR‐, RS‐, and SS‐ractopamine). 0.2∼0.5% (wt.%) of the less bioactive isomers were able to be determined using this method. The method was also able to quantitate ractopamine isomers extracted from the feed premix for swine. The recovery of RR‐ractopamine from the feed premix was 92.6 ± 4.6%.

Keywords:

• Ractopamine
• Capillary electrophoresis
• Cyclodextrins
• Multiple chiral centers

Acknowledgments

The authors thank Drs. Robin Readnour and Michael Turberg for their useful discussions and valuable support.