Simple and high-sensitivity colorimetric analysis of cadmium using homogeneous liquid-liquid extraction.

Colorimetric determination with dithizone (diphenylthiocarbazone) is a simple method that has been applied to analyze cadmium (Cd) ions in water. However, determining concentrations close to the environmental standard value (3 μgL-1) using this method is difficult because of its low sensitivity. Herein, we exploited the phase separation phenomenon to generate a small amount of the extraction phase by adding a mixture of 2-propanol and a small amount of chloroform to a water sample, as a pre-concentration method for the Cd(II) ions. The obtained Cd(II)-dithizone complex was successfully extracted into this phase. We then constructed a simple and highly sensitive colorimetric analysis method for the ppb level of Cd(II) using this phase separation technique.