Spectrophotometric determination of cadmium with 1-(2-pyridylazo)-2-naphthol and non-ionic surfactants Application to acetic acid extracts of ceramic enamels.

The Cd-PAN system in the presence of non-ionic surfactants (polyoxyethylene nonylphenols), which dissolve the reagent and complex by formation of micelles, has been studied spectrophotometrically. The optimum conditions for Cd determination are pH 9 (Na(2)B(4)O(7)-HClO(4)), 2% of surfactant and measurement at 555 nm. The complex is Cd(PAN)(2) and its conditional formation constant is 3.5 x 10(11). The system obeys the Lambert-Beer law, with an error of 0.9% over the Cd concentration range 0.44-1.74 ppm; the molar absorptivity is 4.94 x 10(4)1.mole(-1).cm(-1) at 555 nm. The relative standard deviation is 0.7% and the limit of detection 0.009 mug ml . The selectivity with respect to species important in the ceramic industry is adequate for application of the method to determination of Cd in acetic acid extracts of ceramic enamels.