Spectrophotometric determination of nitrate and nitrite in natural water and sea-water.

Nitrate and nitrite in natural waters are determined spectrophotometrically by passage through an amalgamated zinc reductor at pH 3.4 into iron(III)-Ferrozine solution. Interference by high levels of nitrite is eliminated by treatment with azide. Levels as low as 0.2 mug ml (expressed as nitrogen) can be determined with a precision of +/- 3%.

Indirect spectrophotometric determination of micro-amounts of Tin(II) in the presence of Tin(IV) and in dental gels.

A method for determining microgram amounts of tin(II) in synthetic samples containing tin(IV) and in dental gels has been developed. The procedure involves the oxidation of tin(II) with iron(III) in hydrochloric acid and spectrophotometric determination of the resulting iron(II) as a FerroZine complex.