Visible spectrophotometric determination of cephalosporins and penicillins by indophenol derivatization with and without alkaline degradation to ammonia

Chromatographic analysis of penicillins in pharmaceutical formulations and biological fluids

Natural penicillin (benzylpenicillin) is the oldest antibiotic observed by Alexander Fleming in 1928. To broaden its spectrum of activity, natural penicillin was modified, giving rise to a group of antibiotics under the name 'penicillins'. Although an increasing number of bacteria appear to be resistant to them, penicillins are used to treat a variety of bacterial infections including Gram-positive, Gram-negative aerobic and anaerobic bacteria. Consequently, they are widely used in human and veterinary medicine to prevent and treat diseases. This review covers the analytical methodologies, mainly chromatographic, employed to the penicillins determination in pharmaceutical formulations, biological fluids and in production-scale fermentations reported in the literature. Results of published assays are comparatively presented focusing on sample preparation regarding isolation and purification, chromatographic conditions and method validation. Information on chemical structure, spectrum of activity and action mechanism of common penicillins has also been given.

Spectroscopic analytical study for the charge-transfer complexation of certain cephalosporins with chloranilic acid

Studies were carried out to develop a simple, rapid and accurate spectrophotometric method for the analysis of fifteen cephalosporins. The method depends on the charge-transfer complexation reaction between any of these drugs as an n-electron donor and p-chloranilic acid (p-CA) as a pi-acceptor to form a violet chromogen measured at 520 nm. Different variables affecting the reaction were studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9986-0.9996) were found between the absorbances and the concentrations of the studied drugs in the range of 4-1,200 microg ml(-1). The limits of assay detection ranged from 2.54 to 42.83 microg ml(-1). The accuracy and precision of the method were satisfactory. The method was successfully applied to an analysis of the studied drugs in their pharmaceutical formulations; the recovery percentages ranged from 96.76 +/- 0.87% to 100.50 +/- 1.30%. The interaction sites were confirmed by UV/VIS, IR, 1H-NMR techniques. Molecular modeling for the interaction was used for deriving an equation for calculating the epsilon value for a particular drug. This equation gave a perfect prediction for the degree of interaction of the investigated drugs with the p-CA reagent.

Indirect polarographic and cathodic stripping voltammetric determination of cefaclor as an alkaline degradation product

Cefaclor is not reducible at a mercury electrode, but it can be determined polarographically and by cathodic stripping voltammetry as its initial alkaline degradation product which is obtained in high yield by hydrolysis of cefaclor in Britton-Robinson (B-R) buffer pH 10 at 50 degrees C for 30 min (reduction peak at pH 10, -0.70 V). Differential pulse polarographic calibration graphs are linear up to at least 1 x 10(-4) mol/l(-1). Recoveries of 93% of the cefaclor (n = 3) were obtained from urine spiked with 38.6 microg/ml(-1) using this polarographic method with 1 ml urine made up to 10 ml with pH 10 buffer. Using cathodic stripping voltammetry and accumulating at a hanging mercury drop electrode at - 0.2 V for 30 s, linear calibration graphs were obtained from 0.35 to 40 microg/ml(-1) cefaclor in B-R buffer pH 10. A relative standard deviation of 4.2% (eta = 5) was obtained, and the limit of detection was calculated to be 2.9 ng/ml(-1). Direct determination of cefaclor in human urine (1 ml of urine was made up to 10 ml with pH 10 buffer) spiked to 0.39 microg/ml(-1) was made (recovery 98.6%).

Penicillins and cephalosporins. Physicochemical properties and analysis in pharmaceutical and biological matrices

Penicillins and cephalosporins belong to the most prescribed antibiotics. Despite the relatively extended knowledge of these drugs, the qualitative and quantitative analysis of the compounds still gives rise to many problems. These difficulties are due to the chemical instability of the common beta-lactam nucleus, the minor differences in chemical structures between the analogues, and the complex and relatively fast degradation of the compounds in aqueous solutions. In this review a compilation of the physicochemical properties, the degradation routes and methods for analysis of these substances in biological and other matrices is presented.