Abstract
A highly sensitive method for the determination of trace amounts of manganese(II) with dithizone (H2Dz) was established. This method is based on the complex formation of an adduct, Mn(HDz)2(phen). The extracted complex has an absorption maximum at 507 nm and the absorbance is stable at least for 1 h. The analytical procedure is as follows: Take a sample solution containing less than 5 μg of manganese(II) in a separatory funnel, then add each 2.0 ml of 10% tartrate solution and hydroxylamine hydrochloride solution. Adjust the pH of the solution to about 6.0 by adding hydrochloric acid or ammonia. Extract the coexisting ions preliminarily using 5 ml of 0.02% dithizone solution in chloroform for 30 min. After washing the aqueous phase with a few milliliters of chloroform, extract manganese (II) with 10 ml of 0.001% dithizone and 0.01 M ο-phenanthroline in chloroform by shaking for 1 min. Allow the phases to separate, measure the absorbance of the organic phase at 507 nm against thereagent blank. Under the optimum conditions, a proportionality between the absorbance and manganese (II) concentration was obtained below 5.0μg of manganese(II). The molar absorptivity was obtained to be 4.6×104 dm3 mol-1 cm-1, the sensitivity being 0.0011 μg Mn/cm2. The coefficient of variation of the absorbance measurments for 3.0 μg of manganese(II) was 1.3%. No interference with the determination of 3.0 μg of manganese (II) was found for each 100 μg of copper (II), iron(II), zinc(II), and cadmium(II), and for each 40 μg of cobalt(II), nickel(II), zinc(II), mercury (II) and 10μg of chromium(III). The method was applied to the determination of manganese(II) in carbonate rocks and hot spring waters.
