R.A. Vasantha

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, Beers 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.

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.

Spectrophotometric determination of folic acid in pharmaceutical preparations by coupling reactions with iminodibenzyl or 3-aminophenol or sodium molybdate-pyrocatechol

Novel coupling reagents are used for the simple and sensitive spectrophotometric determination of folic acid either in pure form or in its pharmaceutical preparations. The methods are based on the probable diazotization of the p-aminobenzoylglutamic acid obtained after reductive clevage of folic acid, followed by either coupling with iminodibenzyl to give a violet product with lambda(max) of 580nm or coupling with 3-aminophenol to produce an orange yellow-colored product with lambda(max) of 460nm. Sodium molybdate and pyrocatechol are used in the third method and the pale red-colored product formed has a lambda(max) of 490nm. The methods are highly reproducible and have been applied to the determination of folic acid in tablets and the results compare favorably with the official method. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods.

Iminodibenzyl as a novel coupling agent for the spectrophotometric determination of sulfonamide derivatives.

A rapid, selective and simple spectrophotometric method for the determination of sulfa-drugs is described. The method is based on the formation of violet colored azo product by the diazotization of sulfonamides, viz. sulfathiazole (SFT), sulfadiazine (SFD), sulfacetamide (SFA), sulfamethoxazole (SFMx), sulfamerazine (SFMr), sulfaguanidine (SFG) and sulfadimidine (SFDd) followed by a coupling reaction with iminodibenzyl in alcohol medium. Absorbance of the resulting violet azo product is measured at 570-580 nm and is stable for 24 h at 27 degrees C. Beers law is obeyed in the concentration range of 0.05-6.0 microg ml(-1) 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. The method offers the advantages of simplicity, rapidity and sensitivity without the need for extraction or heating. A reaction mechanism is proposed for the formation of the violet azo product.

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.

Novel reagents for the sensitive spectrophotometric determination of flutamide, an anticancer drug in pharmaceutical preparations

Simple and sensitive spectrophotometric methods for the determination of flutamide (FLA) in either pure form or in its pharmaceutical preparations are described. The first method is based on the diazotisation of reduced FLA, followed by coupling with alcoholic iminodibenzyl (IDB) in acid medium to give a purple coloured product having a lambda(max) of 570 nm. In the second method, the diazotisation of reduced FLA followed by coupling with 4-amino-5-hydroxy-2,7-naphthalenedisulphonic acid monosodium salt (AHND) in a buffer medium of pH 12, gives a red coloured product having a lambda(max) of 520 nm. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods. 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.

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.

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. Beers 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.

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 Beers 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 Beers 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.

Highly sensitive reaction of tryptophan with p-phenylenediamine

A simple and sensitive spectrophotometric method for the determination of tryptophan (TRP) is described. The method is based on the coupling reaction of tryptophan with diazotized p-phenylenediamine dihydrochloride (PPDD) in sulfuric acid medium to give the colored product having an absorption maximum at 520 nm. The coupled product was stable for 2h. Beers law is obeyed in the tryptophan concentration range of 0.25-11 microg/ml. The method is applied for the analysis of pharmaceutical preparations of tryptophan and also in protein samples for tryptophan. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed method and the significant feature of the method is that most of the amino acids do not interfere in the determination of tryptophan.