Flow-injection spectrophotometric determination of certain cephalosporins based on the formation of dyes.

A flow-injection spectrophotometric method is described for the determination of cefadroxil (I) and cefotaxime (II). The method is based on the hydrolysis of the cephalosporin with sodium hydroxide whereby the sulfide ion is produced. The latter is allowed to react with N,N-diethyl-p-phenylenediamine sulfate (N,N-DPPD) and Fe (III), and the blue color produced is measured at 670 nm (method A). Linear calibration graphs are obtained in the range 36.34-109.2 and 95.48-477.4 microgml(-1) for I and II, respectively. The experimental limits of detection (three times the noise signal) are 0.036 and 0.048 microgml(-1) for I and II, respectively. The total flow-rate is 5.3 ml min(-1) for both drugs. Alternately, the sulfide ion produced is allowed to react with p-phenylenediamine dihydrochloride (PPDD) and Fe (III), and the violet color produced is measured at 597 nm (method B). Linear calibration graphs are obtained in the range 0.5-400 and 0.5-450 microg ml(-1) for I and II, respectively. The limits of detection are 0.4 and 0.2 microg ml(-1) for I and II, respectively. The total flow-rate is 3 ml min(-1) for both drugs. The methods have been successfully applied to the analysis of some pharmaceutical formulations, particularly of the injection and capsule types. The relative standard deviation (RSD) (n = 10) at the 50 and 100 microg ml(-1) levels of I and II were 0.83-0.77 and 0.9-0.8% with N,N-DPPD and PPDD as reagents, respectively. Recoveries were quantitative; the results obtained agreed with those obtained by other reported methods.

Kinetic spectrophotometric methods for the quantitation of triprolidine in bulk and in drug formulations.

A kinetic method for the accurate and sensitive determination of triprolidine has been described. The method is based on the alkaline oxidation of triprolidine with KMnO(4). At a fixed time of 20 min, the formed manganate ion is spectrophotometrically measured at 612 nm. The concentration of triprolidine is calculated using the calibration equation for the fixed time method. Beer's law was obeyed from 6 to 40 microg ml(-1) and the R.S.D. (n=10) was 0.97%. Recovery was 99.80%. The method is suitable for quantitative determination of triprolidine in the presence of co-formulated drugs, since pseudoephedrine hydrochloride, which is frequently co-formulated with triprolidine did not interfere with this assay. The intra- and inter-day R.S.D. values indicated the ruggedness of the method. The method has been applied successfully to commercial tablet dosage form. The results obtained agreed with those obtained by the BP method. The determination of triprolidine by the fixed-concentration and rate constant methods is feasible with the calibration equations obtained, but the fixed time method proves to be more applicable.