Multianion analysis, miscellaneous methods - Determination of Anions in Natural and Treated Waters - page 717

14.2 Spectrophotometric methods
14.2.1 Non saline waters
14.2.1.1 Phosphate, nitrate and nitrite
Skjemstad and Reeve [7] have reported three automated procedures for the simultaneous
determination of phosphate, ammonia and nitrate plus nitrite at µg L −1 levels in non
saline waters. Phosphate is estimated by reaction with molybdate and reduction to
molybdenum blue with ferrous ammonium sulphate. Ammonia is determined by the
salicylate/ dichloroisocyanurate reaction in the presence of nitroprusside after in-line
distillation. Nitrate plus nitrite is estimated by using an in-line copperised cadmium
reductor, diazotising the nitrite with sulphanilamide and coupling with N -1-
naphthylethylenediamine. Mercuric chloride used as a preservative does not interfere in
these procedures.
14.2.2 Potable water
14.2.2.1 Phosphate and arsenate
Matsubara et al. [8] determined trace amounts of phosphate and arsenate in potable water
by Spectrophotometric detection at 627nm of their heteropoly acid-malachite green
aggregates following preconcentration by nitrocellulase membrane filtration.
14.2.3 Waste waters
14.2.3.1 Chlorite, nitrite and nitrate
Canelli [9] has described an autoanalyser-based procedure for the simul-taneous
determination of chlorite (and nitrite and nitrate) in waste water.
14.2.3.2 Thiocyanate, cyanate and cyanide
Luthy et al. [10] have described a spectrophotometric method for the determination of
thiocyanate and cyanide in coal gasification waste waters. They showed that the copper
pyridine method with pre-extraction was applicable but that high concentrations of
carbonate and sulphide must first be removed from the sample.
Botto et al. [11] used p-phenylenediamine as the chromogenic reagent in the
spectrophotometric determination of thiocyanate and uncomplexed cyanide in waste
water.