ABSTRACT
An indirect spectrophotometric method has been developed for trace determination of silicate in aqueous samples. The silicate is converted into silicomolybdic acid and extracted into a mixture of 1-butanol and butyl acetate. The silicomolybdic acid is then decomposed with sodium hydroxide and the molybdenum(VI) reduced to molybdenum(III) with a Jones reductor, followed by reoxidation to molybdenum(VI) with iron(III). The resulting iron(II) is complexed with ferrozine, and the absorbance of the complex measured at 562 run. In this manner, submicroamounts of silicate can be determined.
ABSTRACT
The determination of orthophosphate in aqueous media by differential pulse polarography is described. It is based on determination of the molybdenum in 12-phosphomolybdic acid. High sensitivity is achieved by measuring the polarographic wave due to the catalytic reduction of perchlorate or nitrate in the presence of molybdenum(VI). The method is suitable for samples as small as 3.5 ml which contain as little as 9 ng of phosphorus per ml. The average relative deviation is 3.0% at the 0.045 mg/l. phosphorus level and 1.6% at the 1.2 mg/l. level. Results for the analysis of EPA quality-control water and real surface-water samples are reported.
