Large‐volume sample stacking combined with separation by 2‐hydroxypropyl‐β‐cyclodextrin for analysis of isoxyzolylpenicillins by capillary electrophoresis

Abstract

A simple, quick and sensitive capillary electrophoretic technique has been developed for the pharmaceutical analysis of isoxazolylpenicillins (oxacillin, cloxacillin and dicloxacillin) at trace levels for the first time. This method comprises large-volume sample stacking using the electroosmotic flow (EOF) pump (LVSEP), separation using 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as selective complex-forming background electrolyte additive, and direct UV detection. A complete resolution was achieved in the optimal background electrolyte containing 5.2 mM HP-beta-CD. LVSEP was successfully applied in their determinations to improve the sensitivity, where the EOF in the buffer zone was suppressed by using an acidic buffer with pH 3.6. The detection limits of the current technique were found to be 2.0 microg/L for each of the isoxazolylpenicillins based on the signal-to-noise ratio of 3. The curves of peak response versus concentration were linear from 5.0 to 400.0 microg/L with regression coefficients of 0.9982, 0.9986 and 0.9976, respectively. The interaction of isoxazolylpenicillins with HP-beta-CD was discussed. The association constants for complexes of HP-beta-CD with isoxazolylpenicillins were determined by electrophoretic method. The obtained association constants were 27.3, 34.9, and 48.5 M(-1), respectively, being proportional to their hydrophobic properties and steric hindrances. A simple and easy-manipulative sample preparation method was developed and validated by analyzing commercially available milk samples. It was found that with current sample preparation process and instrumentation system, 0.1 mL of milk sample is enough for the analysis of isoxazolylpenicillins to meet European Union (EU) guideline of 30 microg/kg.

On-line Sample Preconcentration by Large-volume Sample Stacking with an Electroosmotic Flow Pump (LVSEP) in Microscale Electrophoresis

“…In the first coupling of LVSEP with the CD-based separation mode, Zhu et al analyzed "achiral" isoxazolylpenicillins by LVSEP-CDCZE using an acidic BGS and 2-hydroxypropyl-β-CD (HP-β-CD) as the EOF suppressor and selective complexforming BGS additive, respectively. 44 The addition of HP-β-CD into the BGS could improve the separation of isoxazolylpenicillins. LVSEP was also successfully applied to improve the sensitivity, where the detection limits were found to be 2.0 μg/L.…”

Contemporary sample stacking in CE: A sophisticated tool based on simple principles

“…A detection limit of 40 ng/mL was reached for each analyte. Zhu et al [74] described a method for analysis of isoxyzolylpenicillins using phosphate buffer containing 2-hydroxypropyl-b-CD as the selective complex-forming agent. The method was applied to the determination of isoxyzolylpenicillins in milk and linearity was obtained in the range between 5.0 and 400.0 mg/L (European Union guideline -30 mg/kg).…”

Cloud point preconcentration prior to capillary zone electrophoresis: Simultaneous determination of platinum and palladium at trace levels

“…In other cases, the low concentration levels, especially in environmental or clinical samples, are not compatible with the detection limits of these techniques. Consequently, preconcentration techniques in conjunction with CE represent a promising tool especially in the area of simultaneous determination of metals at subtrace levels [26][27][28]. Indeed, there is a continuing need for the development of alternative extraction/enrichment procedures which are safe, rapid, convenient, and accurate.…”