Spectrophotometric determination of cadmium (II) with 5-(2 '-carbomethoxyphenyl)azo-8-quinolinol in presence of sodium dodecylsulphate as surfactant

The reaction between cadmium (II) and 5-(2 ' -carbomethoxyphenyl) azo-8-qui nolinol in aqueous medium at pH 4.0-4.8 results in an insoluble complex. Ad dition of sodium dodecylsulphate gives a vermillion red coloured solution w hich is stable for at least 8 h. Beer's law is obeyed in the range 0.04-0.8 8 ppm of cadmium (II) at 503 nm. The molar absorptivity and Sandell's sensi tivity at 503 nm are 1.05 x 10(5) 1 mol(-1) cm(-1) and 1.0 ng cm(-2), respe ctively. Alkali metals, alkaline earths, manganese (II) and chromium (VI) d o not interfere. The interference of Cu(II), Pb(II), Ni(II), Fe(III), Co(II ) and Mo(VI) is removed by extracting their complexes formed with the reage nt at pH 5.5-6.5 in to methyl isobutyl ketone. However, Zn(II) and Hg(II) i nterfere. The method has been applied for the determination of cadmium (II) in borewell, tap and river and nallah (with suspected discharge of industr ial waste) water samples. The results agree closely with the values obtaine d by atomic absorption spectrophotometry.