FLOW-INJECTION SPECTROPHOTOMETRIC DETERMINATION OF PHOSPHATE USING CRYSTAL VIOLET

Phosphate can be determined spectrophotometrically at 560 nm based on the reaction of 12-molybdophosphate and Crystal Violet using flow-injection analysis. The carrier stream was 0.5% (w/v) poly(vinyl alcohol) solution and the reagent streams were 0.1 M sodium molybdate, 5 x 10(-4) M Crystal Violet and 12.5% (v/v) nitric acid. The injection rate was 60 h-1. The calibration graph was linear up to 5.0-mu-g ml-1 phosphate and the relative standard deviation for the determination of 1.0-mu-g ml-1 of phosphate was 0.69% (n = 10). The detection limit was 0.02-mu-g ml-1 phosphate, based on an injection volume of 250-mu-l. The system was applied to the determination of phosphate in fertilizer and waste water samples.