FLOW-INJECTION CHEMILUMINESCENCE DETERMINATION OF COBALT(II) AND MANGANESE(II)

Flow-injection analysis (FIA) was applied to the determination of Co(II) and Mn(II). The method is based on the measurement of metal-catalysed light emission from luminol oxidation by potassium periodate. The apparatus consists of a flow-injection analysis system with a flow cell formed by a spiral of transparent tubing suitable for chemiluminescence measurement. Potassium periodate, unlike hydrogen peroxide, which is the oxidant normally used in luminol chemiluminescence systems, is very stable, gives a low baseline and does not generate bubbles in the tubes of the FIA system. The typical signal is a narrow peak, in which the height is proportional to the light emitted and hence to the concentration of metal ions. The detection limit of Co(II) is 0.01 ng ml-1 and the linear range extends up to 12 ng ml-1; for Mn(II) these limits are 0.02 and 9 ng ml-1, respectively. The optimum concentrations for the reagents are 10(-3) M luminol in Na2CO3-KOH buffer (pH 12.9) and 10(-4) M KIO4 in water. The optimum flow-rates are water 11.1 ml min-1, luminol 2.5 ml min-1 and KIO4 solution 2.1 ml min-1. Interferences by several metal ions were examined.