U. Muralikrishna

Analytical uses of charge-transfer complexes: determination of pure and dosage forms of piperazine

The charge-transfer interaction of piperazine with benzoquinone and its halo derivatives was used for the simple spectrophotometric determination of piperazine in chloroform medium. The sensitivity of the method and the time stability of the charge-transfer complexes were found to depend on the electron affinity of the quinones. The drug-base in different dosage forms was extracted into chloroform after alkali treatment and the piperazine was assayed. The method is sensitive and rapid and the base tolerates a wide variation of reagent concentration. The results compare well with the official BP method.

Spectrophotometric determination of ascorbic acid in pharmaceutical preparations and fruit juices

Conditions were established for the determination of ascorbic acid using phsophovanadotungstic acid as reagent. The method was applied to the determination of ascorbic acid in pure form, pharmaceutical preparations and fruit juices. The method is sensitive (2-24 micrograms ml-1 of ascorbic acid) and rapid and tolerates the presence of common ingredients usually found in fruit juices. The results obtained with the proposed method showed good agreement with those given by the standard method.

A simple spectrophotometric determination of some chlorobenzoquinones with morpholine, thiomorpholine and piperazine.

A spectrophotometric method for the determination of 2,5-dichloro-, 2,6-dichloro- and 2,3,5,6-tetrachloro-1,4-benzoquinones is based on the yellow products of their reaction with morpholine, thiomorpholine and piperazine in chloroform.

A new oxidimetric reagent—potassium dichromate in a strong phosphoric acid medium—VIII: Potentiometric titration of molybdenum(VI) and vanadium(V)

A new titrimetric method is described for the determination of molybdenum(VI) involving prior reduction to Mo(V) with an excess of Fe(II) in a concentrated phosphoric acid solution, followed by titration with dichromate. The titration can be done at room temperature and without protective atmosphere. Uranium interferes, but vanadium may be determined simultaneously.

Titrimetric determination of uric acid with manganese(IV) sulfate

Abstract A simple indirect titrimetric determination of uric acid with manganese(IV) sulfate has been proposed. The method is stoichiometric and accurate and can be conveniently adapted for the assay of urinary uric acid.

Some observations concerning the direct titration of nitrite with cerium(IV)

Direct titration of nitrite with cerium (IV), with ferroin as indicator, is shown to give satisfactory results if the acidity is kept between 0.033 and 0.055M at the end-point. Loss of nitrous acid owing to volatilization and decomposition is discussed. From 10 to 60 mg of sodium nitrite can be estimated with a standard deviation of 5 mug and an average error of 0.2%.

Use of tetravalent manganese in solutions of sulfuric acid as an oxidant for the direct titration of nitrite

Abstract Conditions have been worked out for the direct titration of nitrite with manganese(IV) sulfate using ferroin as indicator. The method is suitable for the estimation of 8–60 mg of sodium nitrite with a standard deviation of 0.04, in an acidity range of 0.3 to 0.6 M. The special feature of this method lies in the reagents association with acid and its relatively higher redox potential.

Analytical uses of charge transfer complexes—Determination of piperidines

Abstract A simple spectrophotometric determination of piperidine and some methyl-substituted piperidines has been proposed. The method is based on the blue-colored charge transfer complex formation of the nitrogen bases with tetrachloro-1,2-benzoquinone in chloroform. The method is rapid and sensitive to 5.5 μg ml−1 piperidine and has the applicability for the assay of piperidine hydrochloride.

PMR Spectra of Piperidine Involved in the Formation of Charge Transfer Complexes with 1,4-Benzoquinones

Abstract The proton magnetic resonance spectra of piperidine involved in the formation of charge transfer complexes with 1,4-benzoquinones, in chloroform, have been presented and discussed.

Some observations on the sodium arsenate assisted oxidation of ascorbic acid by phosphomolybdic acid

Abstract A simple and direct spectrophotometric method for the estimation of ascorbic acid, at the microgram level, based on its reducing action on phosphomolybdic acid in combination with sodium arsenate, has been developed. In the pH range of 1.5 to 3.5, the determination of ascorbic acid in its pure form down to 1 μg/ml is possible. The time of reaction is 20 min and the wavelength of measurement is 710 nm. The method tolerates the presence of common ingredients usually encountered in marketed fruit juices. The method is found to be applicable to the determination of ascorbic acid in pharmaceutical preparations and marketed fruit juices. The results compare well with the standard method.