Separation of related opiate compounds using capillary electrochromatography

Capillary electrophoretic separations have been investigated for six contro lled narcotic analgesic compounds having related structures. Owing to the s imilar charge-to-mass ratios of these compounds, capillary zone electrophor esis failed to provide a satisfactory separation, whereas a baseline-resolv ed separation was achieved in 10 min using micellar electrokinetic chromato graphy. Column efficiencies of 40 000-150 000 plates/m were obtained with a 50 cm long, 50 mu m inner diameter (ID) capillary using 50 mM sodium dodec yl sulfate (SDS) in a 50 mM berate solution containing 12% isopropanol. In contrast, separation of this mixture by capillary electrochromatography pro ved to be significantly superior. The capillary was 15 cm long, with an ID of 75 mu m, and was packed with 1.5 mu m nonporous octadecyl silica (ODS) p articles. The mobile phase consisted of 80% 10 mM tris(hydroxymethyl)aminom ethane (Tris) and 20% acetonitrile, and contained 5 mM SDS. A complete sepa ration was obtained in 2.5 min with an efficiency of 250 000-500 000 plates /m.