DETERMINATION OF CADMIUM BY ION CHROMATOGRAPHY USING 10-(2-PYRIDYLAZO)-9-PHENANTHROL AS A POSTCOLUMN DERIVATIZATION REAGENT

An ion-chromatography method was established for the determination of cadmium using postcolumn derivatization with 10-(2-pyridylazo)-9-phena nthrol (PAP) in a nonionic surfactant solution of Brij 35. The optimum conditions for determining cadmium were: An eluent containing, 0.25 m ol dm-3 lactic acid (pH 3.30) with a flow rate of l ml/min; for the po stcolumn derivatization, a 2 X 10(-4) mol dm-3 PAP solution containing 5% (v/v) dioxane, 4% (w/v) Brij 35, 0.0198% (w/v) sodium borate and 0 .0214% (w/v) sodium hydroxide, at a flow rate of 0.3 ml/min; pH at dra in, 10.3+/-0.1; analytical column, Shim pack IC-Cl (5.0 mm i.d. X 150 mm); oven temperature, 40-degrees-C; injection volume, 20 mul; detecti on at 545 nm. A linear relationship was observed between the peak heig ht and the amount of cadmium within a range of 40 to 200 ppb. The rela tive standard deviation was 1.29% (n=6) for a cadmium concentration of 80 ppb. The detection limit of cadmium was 14.5 ppb (SIN=3). The pres ent method was successfully applied to the determination of cadmium in the Oyster Tissue (NIST 1556a).