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.

Chemiluminescence determination of some fluoroquinolone derivatives in pharmaceutical formulations and biological fluids using [Ru(bipy)(3)(2+)]-Ce(IV) system.

A new chemiluminescence (CL) method using flow injection has been described for the rapid and sensitive determination of three fluoroquinolone derivatives, namely ofloxacin, norfloxacin and ciprofloxacin hydrochloride. The method is based on the CL reaction of the studied fluoroquinolones with tris(2,2'-bipyridyl)ruthenium(II) [Ru(bipy)(3)(2+)] and Ce(IV) in sulfuric acid medium. Under the optimum conditions, the CL intensity is proportional to the concentration of the drugs in solution over the range 0.05-7.0 mug ml(-1) for norfloxacin, 0.05-6.0 mug ml(-1) for ciprofloxacin hydrochloride and 0.003-0.7 mug ml(-1) for ofloxacin. The limits of detection (s/n=3) were 3.1x10(-8) M norfloxacin, 2.6x10(-8) M ciprofloxacin hydrochloride and 5.5x10(-9) M ofloxacin. The method was applied successfully to the determination of these compounds in dosage forms and biological fluids.

Flow-injection chemiluminometric analysis of some benzamides by their sensitizing effect on the cerium-sulphite reaction.

A simple, highly sensitive chemiluminescent method using flow injection is described for the determination of three substituted benzamides, namely: sulpiride, sultopride and tiapride. The method is based on the sensitizing effect of these drugs on the chemiluminometric oxidation of sulphite by cerium(IV). The different experimental parameters affecting the chemiluminescence intensity were carefully studied and incorporated into the procedure. The method permits the determination of 0.05-2.5 mug ml(-1) sulpiride, 0.01-2.5 mug ml(-1) sultopride hydrochloride and 0.01-1.5 mug ml(-1) tiapride hydrochloride with minimum detectability of 0.01 mug ml(-1). The method was applied to the determination of these benzamides in pharmaceutical preparations and biological fluids.

Flow-injection chemiluminometric determination of some thioxanthene derivatives in pharmaceutical formulations and biological fluids using the [Ru(dipy)3(2+)]-Ce(IV) system.

A flow-injection (FI) methodology using tris(2,2'-dipyridyl)ruthenium(II), [Ru(dipy)3(2+)], chemiluminescence (CL) was developed for the rapid and sensitive determination of three thioxanthene derivatives, namely zuclopenthixol hydrochloride, flupentixol hydrochloride and thiothixene. The method is based on the CL reaction of the studied thioxanthenes with [Ru(dipy)3(2+)] and Ce(IV) in a sulfuric acid medium. Under the optimum conditions, calibration graphs were obtained over the concentration ranges 0.002-6 migrograms/ml for zuclopenthixol hydrochloride, 0.5-15 micrograms/ml for flupentixol hydrochloride and 0.05-7.5 micrograms/ml for thiothixene. The limits of detection (s/n = 3) were 4.2 x 10(-9) mol/l zuclopenthixol hydrochloride, 2 x 10(-8) mol/l flupentixol hydrochloride and 4.5 x 10(-8) mol/l thiothixene. The method was successfully applied to the determination of these compounds in dosage forms and biological fluids.

Determination of phenolic sympathomimetic drugs in pharmaceutical samples and biological fluids by flow-injection chemiluminescence.

A rapid and highly sensitive flow-injection chemiluminometric method was developed for determination of 3 sympathomimetic drugs, namely, etilefrine hydrochloride, isoxsuprine hydrochloride, and prenalterol hydrochloride. The method is based on chemiluminescence induced by oxidation of drugs with acidified potassium permanganate in the presence of formic acid as a carrier. The calibration graphs were linear over the concentration ranges 0.2-9, 0.2-12.5, and 0.025-1.25 microg/mL for the 3 compounds, respectively. The method was applied successfully in determining the drugs in dosage forms and in biological fluids. A proposal for the reaction pathway is suggested.

Determination of (S)(-)-cathinone by spectrophotometric detection.

Previous studies on the Khat plant (Catha edulis, Celastraceae) illustrated the importance of using freshly harvested young shoots and leaves such that cathinone, the principle active component and Schedule I controlled drug contained within the plant, could be suitably isolated and identified. The purpose of this work was to develop a quantitative analytical technique for the determination of cathinone. The proposed method is based on treating the reductant cathinone with copper(II)-neocuproine reagent in sodium acetate-buffered medium followed by measuring the absorbance of the copper(I)-neocuproine complex at 455 nm. The calibration plot is linear in the range 0.08-25 micrograms ml-1 with a detection limit of 0.08 microgram ml-1. The precision of the method, expressed as the relative standard deviation, is 1.35% for 10 micrograms ml-1 cathinone. Good recoveries have been obtained in applying the method to the analysis of cathinone in Khat leaves.

Chemiluminescent determination of pyridoxine hydrochloride in pharmaceutical samples using flow injection.

A chemiluminescent method using flow injection is described for the determination of pyridoxine hydrochloride. Its detection limit, linearity and reproducibility were examined. The method is based on the enhancing effect of pyridoxine hydrochloride on the chemiluminescence generated by the oxidation of luminol with hydrogen peroxide in aqueous potassium hydroxide and sodium oxalate. The proposed method is simple and inexpensive. The chemiluminescence intensity is a linear function of pyridoxine hydrochloride concentration over the range 10-250 mug ml(-1) with a detection limit of 6 mug ml(-1). The applicability of the method was demonstrated by the determination of pyridoxine hydrochloride in different tablet formulations and some dietary sources.

Permanganate-based chemiluminescence analysis of cefadroxil monohydrate in pharmaceutical samples and biological fluids using flow injection.

A chemiluminescent method using flow injection is described for the determination of cefadroxil monohydrate. The method is based on the chemiluminescence reaction of cefadroxil with potassium permanganate in sulphuric acid, sensitized by quinine. The proposed procedure allows the determination of cefadroxil over the concentration range 0.1-30 mug ml(-1) with a detection limit of 0.05 mug ml(-1) and a sample measurement frequency of 150 samples h(-1). The method was successfully applied to the determination of cefadroxil in pharmaceutical preparations and biological fluids.

Spectrophotometric determination of methoxamine using cerium(IV) in presence of sodium lauryl sulphate and rhodamine-B.

A sensitive spectrophotometric assay has been developed for the determination of methoxamine in pure dosage form and in its pharmaceutical preparations. The method is based on the acidic oxidation of methoxamine with cerium(IV) in the micellar medium of sodium lauryl sulphate at 96 degrees C. The reaction yields a water-soluble purple product which can be quantified spectrophotometrically at 505 nm. The calibration curve was linear between 1.0 and 20 micrograms ml-1 with a limit of detection 0.5 microgram ml-1. The molar absorptivity at 505 nm is 8.3 X 10(3) iota mol-1 cm-1. The method is simple and rapid since the product is measured directly in solution without extraction.

Colorimetric determination of astemizole in bulk and in its pharmaceutical dosage forms using flow injection.

A continuous flow spectrophotometric method for determining 0.5-100 micrograms ml-1 of astemizole in pure and in dosage forms is suggested. It depends on forming a pinkish orange product which can be quantified spectrophotometrically at 495 nm. The coloured product was due to the action of N-bromosuccinimide on astemizole in alkaline medium and in the presence of a cetyltrimethylammonium bromide micellar medium. The procedure is automated and solutions can be analysed at a rate of 167 h-1 with a relative error of about 1.25%. The limit of detection is 0.5 microgram ml-1 (approximately 1.09 x 10(-6) M). The method is evaluated by a recovery study and by the analysis of commercial formulations.

Chemiluminescence detection of sodium nitroprusside using flow injection analysis.

A simple continuous-flow chemiluminometric method for the determination of 0.05-10 microg/ml of sodium nitroprusside is described. The method is based on the catalyses of luminol oxidation by hydrogen peroxide in alkaline medium. The method is sensitive and requires no sample pre-treatment and solutions can be analysed at a rate of 40 samples/hr with a relative error of about 1.18%. The method was satisfactory for the determination of sodium nitroprusside in a pharmaceutical preparation. The effect of some potential interferents is described.

Kinetic determination of cephalexin in drug formulations.

A kinetic method for the accurate determination of cephalexin has been described. A solution of cephalexin is reacted with 5 x 10(-3)M cobalt(II) nitrate in 1 x 10(-3)M sodium hydroxide at 60 degrees C for a fixed time of 6 min, after which the absorbance of the reaction product is measured at 310 nm. The concentration of cephalexin is calculated by using the corresponding calibration equation for the fixed-time method. The method has been applied to proprietary drugs and the results were compared statistically with those given by the BP method. The determination of cephalexin by the fixed-concentration and rate-constant methods is feasible with the calibration equations obtained but the fixed-time method has been found to be more applicable.

Spectrophotometric determination of cephalexin in dosage forms with imidazole reagent.

A simple spectrophotometric method is proposed for the determination of cephalexin. The method involves acetylation of cephalexin with acetic anhydride in aqueous solution at pH 11.5 to yield alpha-acetamidocephalexin and subsequent measurement at 335 nm of alpha-acetamidocephalexin mercuric mercaptide. The method characterizes a newly developed, sensitive procedure for the determination of cephalexin in different pharmaceutical preparations. The effect of several reaction conditions were investigated. Beer's law was obeyed over the concentration range 30-340 mug/ml. The results compare favourably with those obtained by the official B.P. 1980 method.