Spectrophotometric determination of manganese with 1-(2-pyridylazo)-2-naphthol and a non-ionic surfactant.

A spectrophotometric method for the determination of trace amounts of manganese with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the manganese-PAN chelate solubilized with a non-ionic surfactant, Triton X-100. No extraction procedure is required in the method proposed. High concentrations of calcium, aluminium and magnesium do not interfere. The presence of up to 10 ppm of lead can be tolerated. Iron, cadmium, zinc, cobalt and nickel can be effectively masked with potassium cyanide. Beer's law is obeyed up to 2 ppm of manganese. The molar absorptivity of the manganese-PAN chelate found was 4.4 x 10(4) l. mole (-1). cm(-1) at 562 nm. The overall stability constant of Mn(PAN)(2) in 0.4% Triton X-100 medium is 10(16.8).