Modified liquid junction interface for nonaqueous capillary electrophoresis-mass spectrometry.

Electrospray ionization (ESI) is the most widely used ionization method in on-line coupling of capillary electrophoresis-mass spectrometry (CE-MS). The conventional coaxial sheath flow electrospray interface is currently being replaced by the more sensitive nanoelectrospray technique. The usual limitation of nanoelectrospray CE-MS interface has been its short lifetime caused by deterioration of the metal coating on the CE capillary terminus. This article describes an easy way to construct a more durable and sensitive nanospray interface for nonaqueous CE-MS. In this approach a very thin glass spray capillary (ca. 30 microm outer diameter) is partly inserted inside the CE capillary, the junction being surrounded by the electrolyte medium, which is in contact with the platinum electrode. The interface was tested with five pharmaceuticals: methadone, pentazocine, levorphanol, dihydrocodeine, and morphine. Detection limits ranged from 12 to 540 fmol. Separation efficiency and reproducibility were also studied. The CE current was found to be stable and the migration times were highly reproducible. All the CE separations were carried out in a nonaqueous background electrolyte solution.

Chiral separation and quantitation of pentazocine enantiomers in pharmaceuticals by capillary zone electrophoresis using maltodextrins.

The chiral separation of pentazocine was achieved by capillary electrophoresis using oligosaccharides. Enantiomers were separated on 100 mM Tris/H3PO4 buffer (pH 2.5) with 5% maltodextrin as a chiral selector, and migration behavior was monitored at 200 nm. Under these conditions, (-)- and (+)-pentazocine and dextromethorphan (internal standard) migrated within 9 min, and the resolution of pentazocine enantiomers was 2.54. Linear calibration curves were obtained in the range 5-50 microg/ml(-1) for each enantiomer. The detection limit of pentazocine enantiomers was 29 pg, and the recoveries of(-)- and (+)-pentazocine were 98.9 (R.S.D., 3.4%) and 101.4% (R.S.D., 4.3%) with 10 microg/ml(-1), respectively.

HPLC separation of pentazocine enantiomers in serum using an ovomucoid chiral stationary phase.

A stereospecific HPLC method was developed for the analysis of (-) and (+) pentazocine in human serum. Each enantiomer and the internal standard nalophine were isolated from serum using a liquid-liquid extraction procedure. Recoveries of 99.05 +/- 5.37 and 97.42 +/- 2.78% were obtained for (-) and (+) pentazocine, respectively. Resolution of the enantiomers was obtained by using an ovomucoid chiral stationary phase with a mobile phase of methanol:acetonitrile: 10 mM phosphate buffer, pH 5.8 (20:5.3:74.7 v/v/v). A resolution (Rs) value of 1.80 was obtained for the pentazocine enantiomers. Linear calibration curves were obtained in the 10-100 ng/mL range for each enantiomer in serum. The detection limit based on a signal-to-noise ratio of 3 was 5 ng/mL for each enantiomer in serum using fluorescence detection with excitation at 275 nm and emission set at 335 nm. The lowest quantifiable level was found to be 10 ng for each enantiomer. Precision and accuracy of the method were in the 3.8-4.8% and 1.3-4.2% ranges, respectively.