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A new, rapid and simple method is described and applied to resolve and quantify mixtures of prednisolone acetate, sulfacetamide and phenylefrine. The determination was accomplished by micellar electrokinetic capillary chromatography (MEKC) using a fused silica capillary (57 cm x 75 microm ID). The separation was carried out at 25 degrees C 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 6.5 min and the limits of quantification were about 0.5 mg l(-1) for every component. Repeatability and reproducibility studies achieved were showing no significant differences at 95% confidence level. Then, multivariate calibration regression spectrophotometric methods (PLS-1, PLS-2 and PCR) were applied providing, especially PLS-1, a clear example of the high resolving power of these techniques. The MEKC method has been applied for quantifying these compounds in different commercial pharmaceuticals products and the method gave good results when it is compared with the spectrophotometric method. The pharmaceutical preparations do not require any separation step by the two described procedures.

Two-component mixtures of cefsulodin and clavulanic acid were analysed by a first-derivative spectrophotometric method using a zero-crossing technique of measurement. The relative ease offered by this derivative technique for the quantification of these drugs, with closely overlapping spectral bands, was clearly demonstrated. As the absorption band of clavulanic acid closely overlaps with that of cefsulodin, both direct and derivative spectrophotometric methods have been investigated and evaluated by an exhaustive statistical analysis of the experimental data. The first-derivative spectrophotometric method was found to be more rapid, accurate and reproducible. The procedure does not require any separation step. The calibration graphs were linear in the range 2.0-56.0 micrograms ml-1 for cefsulodin and 2.0-28.0 micrograms ml-1 for clavulanic acid. The lower detection limits of cefsulodin and clavulinic acid (P 0.05 level) were calculated to be 0.16 and 0.24 microgram ml-1, respectively. Mixtures of cefsulodin and clavulanic acid in ratios of 1:4-7:2 were satisfactorily resolved. Both components were also determined in physiological solutions used to prepare intravenous infusions of these antibiotics.

A reverse phase high performance liquid chromatography (HPLC) method to determine dexamethasone phosphate and trimethoprim is described in this paper. The separation was made in a LichrCART® C18 column using an acetonitrile–NaH 2 PO 4 (10 mM) (70:30, v/v) (pH 3) buffer solution as mobile phase. The mobile-phase flow rate and the sample volume injected were 1 ml/min and 20 μl, respectively. The limits of quantification were about 0.25 mg/l for each compound. The method was applied in synthetic mixtures and in pharmaceutical formulations. Analyses were made by preparing test (from the stock solution) method whose results were compared with those obtained by means of the standard addition method. Both methods showed similar results, and then it was proved that some pharmaceuticals claimed levels were in agreement with the obtained results by using our analytical method.

A new, rapid and economical flow-injection method for determining adrenaline and dopamine is proposed on the basis of the hydrolysis of these compounds in alkaline medium. The method was optimized by using a spectrophotometer operating at lambda = 390 nm as detector. Calibration graphs were linear up to 2 x 10(-4) M with quantification limits of 2.5 x 10(-6) M and 3.3 x 10(-6) M for dopamine and adrenaline respectively. Flow-injection allows the measurement of 130 samples per hour. The method was successfully applied for the determination of catecholamines in pharmaceuticals.

A method for the analysis of two-component mixtures of cephalothin and cefoxitin using zero-crossing first-derivative spectrophotometry is described. This technique permits the quantification of these drugs with closely overlapping spectral bands without any separation step. Linear calibration graphs of first-derivative values at 235.00 and 236.75 nm for cephalothin and cefoxitin, respectively, with negligible intercepts were obtained versus concentration in the range 4.0-32.0 micrograms ml-1 for both antibiotics. This paper presents a systematic examination of the experimental data by applying an exhaustive statistical analysis to demonstrate the validity of the method. The results of the determination of these antibiotics in mixtures of injectable dosage forms are also presented, together with their determinations in physiological serum and glucosed physiological serum.

A fluorimetric method has been developed for the quantitative analysis of cefuroxime, based upon the formation of a fluorescent derivative formed by alkaline hydrolysis with 1.0 M sodium hydroxide and heating at 100 degrees C for 60 min. The fluorescent product gave excitation and emission maxima at 380 and 436 nm, respectively. The method was performed in aqueous solution adjusted to pH 10.5 by addition of phosphate buffer solution. The calibration curve was found to be linear in the range of concentrations 0.050-1.70 micrograms ml-1. The lower limit of detection was 1.0 x 10(-2) micrograms ml-1. The method was applied to authentic pharmaceutical preparations containing cefuroxime sodium or cefuroxime axetil, the 1-(acetyloxy) ethyl ester of the drug, and was found to be satisfactory. Cefuroxime sodium was also determined in physiological solutions used to prepare intravenous infusions of this antibiotic.