Analytical applications of photochemical reduction of Azur B by EDTA-iodide determination.
A kinetic study of the photochemical reaction of Azur B and EDTA (in the absence of oxygen) has been made in connection with development of a new kinetic method for iodide. The reaction is first-order with respect to the dye, EDTA and absorbed light-intensity. The rate of photoreduction is strongly pH-dependent, and maximal at about pH 6.8. The photoreduction involves a long-lived excited state of the dye and is dramatically retarded by small amounts of iodide. A tentative mechanism is proposed, and the experimental conditions have been optimized. The variable time method appear to be the most suitable. A detection limit of 1.0 mug/ml and a coefficient of variation of about 3% can be achieved. Chloride and bromide do not interfere at levels below 100-fold mole ratio to iodide. Metal ions do not interfere if enough excess of EDTA is used. Coloured species may interfere at high concentration (filter effect).
Perez-Ruiz
T
T
Department of Analytical Chemistry, C.S.I.C. University of Murcia, Spain.
Martinez-Lozano
C
C
Ochotorena
J
J