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A new, rapid, and simple method is described and used to resolve and quantify mixtures of prednisolone, naphazoline, and phenylephrine. The determination was accomplished by micellar electrokinetic chromatography (MEKC) using a fused-silica capillary (57 cm675 lm ID). The separation was carried out at 258C and 30 kV, using a 5 mM phosphate-5 mM borate buffer adjusted to pH = 8.2, 40 mM sodium dodecylsulfate (SDS) as background electrolyte. Under these conditions, the run time was 6.6 min and the limits of quantification were about 0.4 mg/L for every component. Repeatability and reproducibility studies showed no significant differences at 95% confidence level. Application of multivariate calibration regression spectrophotometric methods (PLS-1, PLS-2, and PCR) clearly demonstrated, especially in the case of PLS-1, the high resolving powder of these techniques if all possible interferences are suppressed. MEKC has been used for quantifying these compounds in different pharmaceutical products and the method gave good results compared with spectrophotometry. The pharmaceutical preparations do not require any separation steps when analysed by the two procedures described.

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SummaryA new, simple, and accurate micellar electrokinetic chromatographic (MEKC) method is clescribed for quantification of hydrocortisone, hydrocortisone hemisuccinate, hydrocortisone acetate, nystatin, oxytetracychne, Zn-bacitracin, polymyxin B, and hdocaine in ocular and cutaneous pharmaceutical products. The separation was performed at 25 ~ and 25 kV, with 15 mM phosphate + 15 mM borate buffer, pH 8.2, and 60 mM sodium dodecylsulfate (SDS) in 10:1 (%, v/v) methanol-water as background electrolyte. Under these conditions the analysis time is approximately 23 min. The method has been used for quantification of these compounds in different commercial pharmaceutical products and gave good results when compared with reference spectrophotometric and HPLC methods.

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A reverse-phase high-performance liquid chromatographic (HPLC) method to determine hydrocortisone acetate, hydrocortisone hemisuccinate and lidocaine is described in this paper. The separation was made in a LichrCART C(18) column using a methanol-NaH(2)PO(4)/Na(2)HPO(4) (0.1 mol L(-1)) (pH=4.5) buffer solution as a mobile phase in isocratic mode (60:40 (v/v)). The mobile phase flow rate and the sample volume injected were 1 mL min(-1) and 20 micro L, respectively. The detection was made with a diode-array detector measuring at the maximum for each compound. Quantification limits ranging from 0.18 to 0.84 micro g L(-1) were obtained when the peak area was measured. The method was applied in pharmaceutical formulations that were compared with those obtained by through multivariate regression spectrophotometry and micellar capillary electrophoresis (MEKC). HPLC results are in accordance with the results obtained by MEKC. The spectrophotometric method was suitable only for synthetic samples.

A new, simple and accurate micellar electrokinetic chromatography (MEKC) method is established for quantification of hydrocortisone, polymyxin B and Zn-bacitracin in local pharmaceutical preparations. The separation was carried out at 25 degrees C and 25 kV, using a 15 mmol L(-1) phosphate-15 mmol L(-1) borate buffer (pH 8.2), 60 mmol L(-1) sodium dodecylsulfate (SDS), and 10% methanol-water (v/v) as background electrolyte. Under these conditions the analysis takes about 23 min. The method has been applied for quantifying these compounds in two different commercial pharmaceutical products and the method gave good results when compared with a reference spectrophotometric multivariate calibration method.

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