Determination of dexamethasone and two excipients (creatinine and propylparaben) in injections by using UV-spectroscopy and multivariate calibrations.

The use of multivariate spectrophotometric calibration for the simultaneous determination of dexamethasone and two typical excipients (creatinine and propylparaben) in injections is presented. The resolution of the three-component mixture in a matrix of excipients has been accomplished by using partial least-squares (PLS-1). Notwithstanding the elevated degree of spectral overlap, they have been rapidly and simultaneously determined with high accuracy and precision (comparable to the HPLC pharmacopeial method), with no interference, and without resorting to extraction procedures using non-aqueous solvents. A simple and fast method for wavelength selection in the calibration step is used, based on the minimisation of the predicted error sum of squares (PRESS) calculated as a function of a moving spectral window.

Simultaneous determination of naphazoline, diphenhydramine and phenylephrine in nasal solutions by capillary electrophoresis.

A capillary zone electrophoresis (CZE) method has been developed to separate and quantitate naphazoline (NAPH), dyphenhydramine (DIP) and phenylephrine (PHE) in nasal solutions. Samples were diluted 1:25 in ultrapure water and injected at the anodic end. A central composite design has been used to optimise the experimental conditions for a complete and fast separation of the active ingredients studied. Critical parameters such as voltage, pH and buffer concentration have been studied to evaluate how they affect responses such as resolution and migration times. Separation was performed on a silica capillary with 75 microm I.D. and 70 cm total length at an applied voltage of 17.7 kV with a phosphate run buffer of pH 3.72 and 0.063 mol l(-1). Calibration curves were prepared for NAPH, DIP and PHE. For each analyte, the correlation coefficients were >0.999 (n=15). The RSD% of six replicate injections for each analyte were reasonably good. The method was applied to the quantitation of the three components in a commercial dosage form. The proposed method has the advantage of needing a very simple sample pretreatment and being faster than a typical HPLC chromatographic method.

Simultaneous spectrophotometric-multivariate calibration determination of several components of ophthalmic solutions: phenylephrine, chloramphenicol, antipyrine, methylparaben and thimerosal.

The use of multivariate spectrophotometric calibration for the simultaneous determination of several active components and excipients in ophthalmic solutions is presented. The resolution of five-component mixtures of phenylephrine, chloramphenicol, antipyrine, methylparaben and thimerosal has been accomplished by using partial least-squares (PLS-1) and a variant of the so-called hybrid linear analysis (HLA). Notwithstanding the presence of a large number of components and their high degree of spectral overlap, they have been determined simultaneously with high accuracy and precision, with no interference, rapidly and without resorting to extraction procedures using non aqueous solvents. A simple and fast method for wavelength selection in the calibration step is presented, based on the minimisation of the predicted error sum of squares (PRESS) calculated as a function of a moving spectral window.