A spectrophotometric assay method for vanadium in biological and environmental samples using 2,4-dinitrophenylhydrazine with imipramine hydrochloride.

A simple, rapid, and sensitive method involving the interaction of 2,4-dinitrophenylhydrazine with imipramine hydrochloride in presence of vanadium (V) in sulfuric acid medium has been proposed for the determination of vanadium. The purple-colored product developed showed an absorption maximum at 560 nm and was stable for 24 h. The working curve was linear over the concentration range of 0.1-2.8 µg ml( - 1), with sensitivity of detection of 0.0124 µg ml( - 1). Molar absorptivity and Sandell's sensitivity were found to be 2.6 × 10(4) l/mol cm and 0.0039 µg cm( - 1), respectively. The accuracy of the proposed method was assessed by Student's t test and variance ratio F test, and the results were on par with the reported method. The method was successfully used in the determination of V in water, human urine, soil, and plant samples, and it was free from interference by various concomitant ions.

3-Aminophenol as a novel coupling agent for the spectrophotometric determination of sulfonamide derivatives.

A rapid, simple and sensitive spectrophotometric method for the determination of some sulfa drugs is described. The method is based on the formation of orange yellow colored azo product by the diazotization of sulfonamides, viz., dapsone (DAP), sulfathiazole (SFT), sulfadiazine (SFD), sulfacetamide (SFA), sulfamethoxazole (SFMx), sulfamerazine (SFMr), sulfaguanidine (SFG) and sulfadimidine (SFDd) followed by a coupling reaction with 3-aminophenol in aqueous medium. Absorbance of the resulting orange yellow product is measured at 460 nm and is stable for 6 days at 27 degrees C. Beer's law is obeyed in the concentration range of 0.05-8.0 microg/ml at the wavelength of maximum absorption. The method is successfully employed for the determination of sulfonamides in various pharmaceutical preparations and common excipients used as additives in pharmaceuticals do not interfere in the proposed method. Plausible reaction mechanism is proposed for the formation of the azo product.

Sensitive spectrophotometric method for the determination of indomethacin in capsules.

A simple, sensitive and selective spectrophotometric method for the determination of indomethacin (INM) either in pure form or in capsules is described. The method is based on the coupling reaction of hydrolyzed INM with diazotized p-phenylenediamine dihydrochloride (PPDD) in sulphuric acid medium to give a red coloured product having the absorption maximum at 510 nm. The product is stable for 20 h. Beer's law is obeyed in the concentration range of 0.2-10 microg/ml. Results of the proposed method compare favourably with those of the official methods and offer the merits of sensitivity and stability. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed method.

Novel coupling reagents for the sensitive spectrophotometric determination of nimesulide in pharmaceutical preparations.

Novel coupling reagents are used for the sensitive spectrophotometric determination of nimesulide (NIME) in either pure form or in its pharmaceutical preparations. The methods are based on the diazotisation of reduced NIME, followed by either coupling with alcoholic iminodibenzyl (IDB) in acid medium to give a deep blue coloured product (lambda(max) of 600 nm) or coupling with 3-aminophenol (AP) in acid medium to produce an orange red coloured product (lambda(max) of 470 nm). Both the methods are highly reproducible and have been applied to a wide variety of pharmaceutical preparations and the results compare favourably with the reported method. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods.

Spectrophotometric determination of metronidazole and tinidazole in pharmaceutical preparations.

Sensitive and simple spectrophotometric methods for the determination of metronidazole (MNZ) and tinidazole (TNZ) in either pure form or in its pharmaceutical formulations are described. The first method is based on the interaction of 3-methylbenzothiazolin-2-one hydrazone (MBTH) with MNZ/TNZ (reduced drug) in presence of copper sulphate and pyridine in acidic medium. The resulting yellowish orange products have lambda(max) of 500 and 490 nm, respectively, for MNZ and TNZ and are stable for about 4 h. The second method describes the reaction between reduced diazotised drugs with N-(1-naphthyl)ethylenediamine dihydrochloride (NEDA) in neutral medium to yield pink products which have lambda(max) of 520 and 505 nm, respectively, for MNZ and TNZ, respectively. The products are stable for more than 24 h. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed method. Both the methods are highly reproducible and have been applied to a wide variety of pharmaceutical preparations and the results compare favourably with those of official methods.

Spectrophotometric methods for the rapid determination of menadione and menadione sodium bisulphite and their application in pharmaceutical preparations.

Two simple, rapid and sensitive spectrophotometric determination of menadione and its sodium bisulphite derivative (MSB) have been carried out. The first method involves the reaction of menadione and its sodium bisulphite derivative with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) is sodium hydroxide medium to give blue coloured product having maximum absorption at 625 nm and the coloured species is stable for more than 1 h. The Beer's law is obeyed in the range 0.4-16 microg ml(-1). The second method proposes the reaction of menadione and its sodium bisulphite derivative with resorcinol in concentrated sulphuric acid medium to give red coloured product having maximum absorption at 520 nm and is stable for 3 h. The Beer's law was obeyed in the range of 1-24 microg ml(-1). Molar absorptivity for the above two methods were found to be 7.6 x 10(3) and 4.5 x 10(3) l mol(-1) cm(-1), respectively. All the measurements were carried out at room temperature. These two methods have been successfully applied for menadione and its sodium bisulphite derivatives in injections and tablets of pharmaceutical formulations. The results compare favourably with official method.

A new sensitive and selective spectrophotometric method for the determination of catechol derivatives and its pharmaceutical preparations.

A sensitive and simple spectrophotometric method for the estimation of certain catechol derivatives like pyrocatechol (PCL), dopamine hydrochloride (DPH), levodopa (LDP), methyl dopa (MDP) and adrenaline (ADH) in either pure form or in its pharmaceutical formulation is described. The method is based on the interaction of diazotised p-nitro aniline (DPNA) with catechol derivatives in presence of molybdate ions in acidic medium. Absorbance of the resulting red complex is measured at 500-510 nm, respectively, and is stable for 2-10 h. The method is highly reproducible and specific for these selected catechol derivatives. The common excipients used as additives in pharmaceuticals and phenol, hydroquinone, resorcinol, pyrogallol and phloroglucinol do not interfere in the proposed method. Analytical data for determination of the pure compound is presented together with the application of the proposed method to the analysis of some pharmaceutical formulations. The results compare favourably with those of official and reported methods.

A sensitive and selective spectrophotometric estimation of catechol derivatives in pharmaceutical preparations.

A sensitive and simple spectrophotometric method for the estimation of catechol and its derivatives like dopamine hydrochloride (DPH), levodopa (LDP), methyldopa (MDP) and adrenaline hydrochloride (ADH) in both pure form and in pharmaceutical formulation, is described. The method is based on the interaction of diazotised sulphanilamide (DSA) with catechol derivatives in the presence of molybdate ions in acidic medium. Absorbance of the resulting red coloured product is measured at 490 nm for pyrocatechol (PCL) and at 500 nm for other catechol derivatives. The colour reaction is stable for 24-30 h. Under optimal conditions, Beer's Law range for pyrocatechol was found to be between 0.04 and 2.4 (R.S.D.=0.78%), for DPH was 0.02-2.8 (R.S.D.=0.98%) for LDP was 0.1-2.8 (R.S.D.=1.21%) for MDP was 0.5-7 (R.S.D.=1.41%) and for ADH was 0.5-7 (R.S.D.=1.58%). The method is highly reproducible and specific for these selected catechol derivatives. The common excipients used as additives do not interfere in the proposed method. Analytical data for the determination of the pure compound is presented together with the application of the proposed method to the analysis of some pharmaceutical formulations. The results compare favourably with those of official and reported methods.