Simultaneous determination of bifonazole and tinctures of calendula flower in pharmaceutical creams by reversed-phase liquid chromatography.

The aim of this research was to develop and validate a sensitive, rapid, easy, and precise reversed-phase liquid chromatography (LC) method for stability studies of bifonazole (I) formulated with tinctures of calendula flower (II). The method was especially developed for the analysis and quantitative determination of I and II in pure and combined forms in cream pharmaceutical formulations without using gradient elution and at room temperature. The influence on the stability of compound I of temperature, artificial radiation, and drug II used for the new pharmaceutical design was evaluated. The LC separation was carried out using a Supelcosil LC-18 column (25 cm x 4.6 mm id, 5 microm particle size); the mobile phase was composed of methanol-0.1 M ammonium acetate buffer (85 + 15, v/v) pumped isocratically at a flow rate of 1 mL/min; and ultraviolet detection was at 254 nm. The analysis time was less than 10 min. Calibration graphs were found to be linear in the 0.125-0.375 mg/mL (rI = 0.9991) and 0.639-1.916 mg/mL (rII = 0.9995) ranges for I and II, respectively. The linearity, precision, recovery, and limits of detection and quantification were satisfactory for I and II. The results obtained suggested that the developed LC method is selective and specific for the analysis of I and II in pharmaceutical products, and that it can be applied to stability studies.

Simultaneous spectrophotometric determination of phenilpropanolamine HCL, caffeine and diazepam in tablets.

A rapid, reliable and specific UV spectrophotometric method was developed to determine Phenilpropanolamine Hydrochloride (I), Caffeine (II) and Diazepam (III) formulated in tablets. This method was validated and compared with a liquid chromatography (LC) procedure used for the simultaneous quantitative analysis of the drugs. The established linearity ranges by both methods for compounds I, II and III were 0.36-0.88, 0.012-0.028 and 0.036-0.084 mg/ml, respectively. The correlation coefficients by HPLC were r(I)(2)=0.997, r(II)(2)=0.999, r(III)(2)=0.999 and by the UV spectrophotometric method were r(I)(2)=0.998, r(II)(2)=0.996, r(III)(2)=0.999. LC and UV methods showed excellent precision and accuracy. As regards precision, LC showed CV values range of 0.2-0.9 and UV 0.15-0.72. On the other hand, accuracy was obtained with CV values range of 0.1-1.8 and 0.32-1.11 for LC and UV, respectively. The recoveries of I, II and III were >98.04% for both methods over the linear range. The UV and HPLC methods have been successfully used to determine the I, II and III content in tablets of different origin.

Qualitative and quantitative reversed-phase liquid chromatography of a new bisisoxazolylnaphthoquinone.

The main objective of this study was to develop and test the applicability of a sensitive, accurate, and precise liquid chromatographic (LC) method for evaluating the stability characteristics of a new bisisoxazolylnaphthoquinone, 2-(3,5-dimethyl-4-isoxazolylamino)-N-(3,5-dimethyl-4-isoxazolyl)-1,4-naphthoquinone-4-imine compound 1. The method was shown to be selective and stability-indicating. Isocratic elution with a mobile phase of methanol-water (75 + 25, v/v) on a reversed-phase column with UV detection at ambient temperature completely resolved compound 1 from its degradation products. The LC system was calibrated by plotting peak responses versus known concentrations of a reference standard by using an internal standardization procedure. Complete elution occurred after 12 min with a peak symmetry factor of 0.95 for the drug peak. The kinetic degradation of compound 1 was studied over a pH range of 0.88-14.00 to determine the kinetic parameters involved in its decomposition path in aqueous solution.