Arsenazo III-spectrophotometry for the determination of thorium content

ABSTRACT

The complexation interaction between arsenazo III chromogenic agent and tetravalent thorium ion (Th⁴⁺) is the theoretical basis for the determination of thorium by spectrophotometry. In this paper, the effects of the acidity, temperature, interfering ions and Th⁴⁺ concentration on the absorbance and stability of arsenazo III-Th⁴⁺ solution by spectrophotometry were systematically studied. The results showed that the solutions to be tested had high absorbance values and stability only when the concentration of hydrochloric acid was greater than 6 mol·L⁻¹. The absorbance decreased only 0.02 when the temperature was changed from 15°C to 40°C. The absorbance of arsenazo III-Th⁴⁺ solution at 662 nm showed a good linear relationship with the concentration of Th⁴⁺ under the same experimental environment (R² = 0.9986), and the apparent molar absorption coefficient was 9.95 × 10⁴ L·mol⁻¹·cm⁻¹, showing that thorium can be accurately quantitatively measured according to the Lambert-Beer law under these conditions.

KEYWORDS:

• Thorium
• Arsenazo III
• spectrophotometry
• absorbance

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [12005095]; the Natural Science Foundation of Hunan Province, China [2022JJ30487 and 2021JJ40447]; the Research and Innovative Experiment Program for College Students in Hunan Province, China (S202210555140, S202310555260 and S202310555170); the Project of Young Backbone Teacher of Hunan Province, China [221RQG004]; the Graduate Research Innovation Project of Hunan Province, China [CX20230975]; the State Foundation for Studying Abroad [202108430096].