RAPID, HIGHLY SENSITIVE AND SELECTIVE SPECTROPHOTOMETRIC DETERMINATION OF CADMIUM(II) AS AN ION ASSOCIATE OF TETRAIODOCADMIATE(II) WITH ASTRA PHLOXINE

A very simple, rapid, highly sensitive and selective non-extractive spectrophotometric method for the determination of trace amounts of cadmium(II) has been proposed. It is based on the formation of ion association complex (IA) between iodide complex of cadmium Cd(II) [CdJ(4)(2-)] and polymethine dye Astra Phloxine FF. The color of the solution changes from red to red-purple. The color of the IA develops completely at temperature less than 18 degrees C after 5-10 minutes after mixing of reagents and remains constant for several hours. Opitmal concentrations of HCl, AP and KJ are 0.07-0.13 M, 1.2x10(-5) M and 6x10(-3) M, respectively. The molar absorptivity of the IA is 6.5x10(4) mol(-1) L cm(-1). The calibration graph is linear between 1x10(-7) and 3x10(-6) mol L-1 of cadmium (II). The limit of detection is 5x10(-8) mol L-1 (l = 5 cm, 0.006 mg L-1). A large excess of over 50 cations, anions and some common complexing agents do not interfere with the determination. The method was successfully applied in the determination of cadmium in Wood's alloy and mine water.