CATALYTIC SPECTROPHOTOMETRIC DETERMINATIO N OF TRACE MOLYBDENUM IN NATURAL-WATER AND TAP-WATER SAMPLES

A sensitive and simple catalytic spectrophotometric method for the det ermination of molybdenum has been developed using the molybdenum-catal yzed oxidation of L-ascorbic acid with hydrogen peroxide in the presen ce of o-phenylenediamine to produce quinoxaline derivatives. The absor bance of the solution was measured at 340 nm for the determination of molybdenum after reacting for 5 min at pH 3.2 and 25 degrees C and rea djusting the pH of the solution to 1 with hydrochloric acid to stop th e reaction. The calibration graph was linear up to 4 ng/ml of molybden um. The detection limit was 0.03 ng/ml (0.2 ng). The proposed method w as successfully applied to river-, rain- and tap-water samples.