Hydroxyamidines as new extracting reagents for spectrophotometric determination of cadmium with 4-(2-pyridylazo)naphthol in industrial effluents, coal, and fly ash.

A simple, sensitive, and selective extractive spectrophotometric method for the determination of cadmium in trace quantities with N1-hydroxy-N1,N2-diphenylbenzamidine (HDPBA) and 4-(2-pyridylazo)naphthol (PAN) is described. The method is based on the extraction of cadmium with HDPBA into chloroform at pH 9.0 +/- 0.2 and simultaneous spectrophotometric determination with PAN. The binary Cd(II)-HDPBA complex extracted into chloroform has a molar absorptivity of 1.96 x 10(4) L/mol/cm at lambda max 400 nm. The sensitivity of the yellow Cd(II)-HDPBA complex was increased remarkably by the addition of PAN to the binary complex. With 6 different hydroxyamidines tested, the red-orange complex in chloroform exhibited maximum absorbance at 530-550 nm, with molar absorptivity values of 3.2-5.6 x 10(4) L/mol/cm. The method adheres to Beer's law up to 1.5 micrograms cadmium/mL organic phase. The detection limit of the method is 0.02 micrograms Cd/mL. Investigations of the effect of foreign ions revealed that the present method is free from matrix interference of most of the common ions (e.g., Fe(III), Ni(II), Cu(II), Mn(II), V(V), Co(II), Al(III), Cu(II), Mg(II), and Mo(VI)). The relative standard deviation for 10 repetitive analyses of the metal was 1.4%. The validity of the method was tested successfully with various environmental samples.