3.2.2. Dithizone concentration
As the principle reagent in this work, dithizone was selected to form Cd–dithizone complex. The effect of dithizone concen-tration on the absorption was investigated, which was shown in Fig. 4. It was found that the absorbance increased with the increasing of chelating reagent concentration in the certain range and at higher concentration of dithizone, the absorbance slightly decreased. Therefore, 0.030mmol L−1of dithizone was chosen for further experiments.