Sequential injection: a new concept for chemical sensors, process analysis and laboratory assays

Analyses of isoniazid using 2-methyl-3-nitropyridine-6-carboxaldehyde

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Ion selective electrodes, potentiometry, and potentiometric titrations.

A rapid and precise continuous-flow method is described for the determination of isoniazid (0050–200 µg ml–1) based on the chemiluminescence produced during its reaction with N-bromosuccinimide in alkaline medium The emission intensity is greatly enhanced by the presence of ammonia The procedure is automated and samples can be analysed at a rate of 112 solutions per hour with a relative error of about 2% When applied to tablets, the method is relatively free from interferences from common excipients and co-existing compounds The results obtained for the assay of commercial preparations compared well with those obtained by an official chemical method and demonstrated good accuracy and precision

Continuous-flow chemiluminescence determination of isoniazid by oxidation with N-bromosuccinimide

Flow injection determination of isoniazid using N-bromosuccinimide- and N-chlorosuccinimide-luminol chemiluminescence systems.

A potentiometric procedure for the assay of isonicotinic acid hydrazide (isoniazid) with vanadium(V) at room temperature is described. The reduction of vanadium(V) to vanadium(IV) by isoniazid in an acidic medium is catalysed by osmium tetroxide, and the application of this method to the assay of isoniazid in pharmaceutical preparations is considered. Oxalic acid interferes in the determination, although commonly used excipients such as starch, dextrin, sucrose, glucose, lactose and gum acacia do not interfere.

A potentiometric procedure for the assay of isonicotinic acid hydrazide (isoniazid)

Determination of isonicotinic acid hydrazide in pharmaceutical preparations

1.

A procedure has been developed for the determination of hydrazine in sulphuric acid solution by direct electrometric titration with cerium(IV) sulphate at 50–55° C using manganese(II) or chromium(III) sulphate as catalyst. The average CeIV-hydrazine ratio has been found to be 1.016. If the titre values are multiplied by the average correction factor of 0.985, one gets a correct assay of the hydrazine taken with an error of ±0.2%. The method now proposed has two advantages namely (1) that it is a direct procedure not involving the intermediate use of ferricyanide and (2) that the consumption of ceric sulphate is about a quarter of what is required in the existing methods involving the intermediate use of ferricyanide. Even in the direct bromate titration, the consumption of oxidant is four times of what it is in the procedure now recommended.




2.

Other catalysts like iodine monochloride (in hydrochloric acid medium) osmic acid, silver sulphate, ferric sulphate and molybdic acid in sulphuric acid medium have been tried without success.




3.

Titrations are not possible with a visual indication of the end point by the use of ferroin, n-phenyl anthranilic acid or triphenyl methane dyes as internal indicators.

Electrometric titration of hydrazine with cerium (IV) sulphate

The orange yellow colour of the vanadium(V)-isoniazid complex measured at 420 nm (Filter No. 42) is utilized as the basis for the colorimetric determination of isoniazid in the pH range 1.8 to 2.2. Beer's law is obeyed in the range 0.67–13.6 ppm. The influence of the substrates that are commonly employed as excipients in pharmaceutical preparations has been studied. The reliability of the method was tested by applying to the determination of isoniazid in “Isokin” tablets. Results are in good agreement with those obtained by the official B. P. method.

Colorimetric determination of microgram quantities of isonicotinic acid hydrazide (isoniazid).

A method has been developed for the titration of cerium(IV) sulphate with sodium oxalate at the room temperature, using ferroin as internal indicator. A new principle has been utilised for facilitating the indicator action at the equivalence point. This involves the use of a photochemical reaction between the oxalate and iron(III) which is deliberately added to the mixture containing cerium(IV) sulphate and ferriin. When the mixture is titrated with the sodium oxalate solution under exposure to the light from a Philips „Repro lamp“, the addition of a very slight excess of sodium oxalate solution, after all the cerium(IV) sulphate has reacted, produces a vivid red colour. The slight excess of sodium oxalate added reacts with the iron(III) salt photochemically producing a trace of iron(II) salt which reduces the ferriin to the red ferroin. In titrations with 0.1 and 0.05 N solutions of sodium oxalate, the error is negligible. In titrations with sodium oxalate solution of lower strengths, the error amounts to 0.02 ml of 0.01 N oxalate which has to be subtracted from the titre.

P. V. Krishna Rao

Papers

A potentiometric procedure for the assay of isonicotinic acid hydrazide (isoniazid)

Determination of isonicotinic acid hydrazide in pharmaceutical preparations

Electrometric titration of hydrazine with cerium (IV) sulphate

Colorimetric determination of microgram quantities of isonicotinic acid hydrazide (isoniazid).

Titration of cerium (IV) sulphate with sodium oxalate at the room temperature using ferroin as internal indicator