Simultaneous determination of amoxycillin and dicloxacillin in capsules by potentiometric titrimetry and high-performance liquid chromatography.

Direct potentiometric titration and two HPLC conditions for the simultaneous determination of amoxycillin and dicloxacillin in their capsules have been developed. One-run titration utilizing 0.05M acet. HClO(4) enables the quantification of both antibiotics. The HPLC-separation could be undertaken on reversed phase, LiChrosorb RP-18 (10 mum), and LiChrospher 100 RP-18 (5 mum), columns by using mobile phases containing acetonitrile + 1% aq, acetic acid, in proportions of 47:53 or 39:61 (v/v), respectively, at a flow rate of 1.5 ml/min with UV-detection at 240 nm. Recoveries of the individual drugs by the application of each described method were found to be fairly satisfactory.

Spectrophotometric quantification of astemizole and its demethylated metabolite in urine after TLC separation.

The coupling of TLC and UV measurement for determination of astemizole and its main metabolite, O-demethylated derivative, in urine has been investigated. The metabolite like the drug absorbs maximally at almost the same wavelengths, which makes their simultaneous UV determination in biological fluids quite inapplicable. TLC separation on silica gel F254 utilizing chloroform/methanol (85:15, v/v) achieved the best fractionation of the two compounds from the matrix-components of urine. Concentration levels of 0.5-140 micrograms/ml (ppm) in worked-up sample could be reached by adopting the spectrophotometric measurements at 286 nm for ethanolic extracts of the silica layers carrying each individual compound against a blank silica. Varying levels of the intact drug and its phenolic primary metabolite could be accurately traced in urine samples following a 10 mg single oral dose (approximately 12.5 micrograms/kg) after different time intervals up to 12 h. Synthetic preparation of the metabolite by demethylating astemizole is mentioned and its physicochemical characterization is briefly discussed.

Spectrophotometric determination of amoxycillin and clavulanic acid in pharmaceutical preparation.

A spectrophotometric procedure for the simultaneous determination of amoxycillin and clavulanic acid in some pharmaceutical preparations has been developed. As the absorption bands of amoxycillin (274 and 227 nm) and clavulanic acid (270 nm) overlap, both Vierordt's method and derivative spectrophotometry have been investigated and evaluated. The first-derivative spectrophotometric method was found to be more accurate, direct and reproducible.