Analytical Sciences

Abstract − Analytical Sciences, 27(5), 471 (2011).

On-site Catalytic Determination of Trace Manganese in Fresh Water Using Oxidation of Malachite Green with Periodate
Junpei SHINDO,*,** Junji KOJIMA,* Yasutada SUZUKI,*** and Susumu KAWAKUBO*
*Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Takeda, Kofu 400-8511, Japan
**Environmental Technology Center Co., Ltd., 1-8 Kanda-Ogawamachi, Chiyoda, Tokyo 101-0052, Japan
***Center of Instrumental Analysis, University of Yamanashi, Takeda, Kofu 400-8511, Japan
An on-site determination method for trace manganese has been developed using the manganese-catalyzed oxidation of Malachite Green (MG) with potassium periodate. Absorbance measurement of MG was carried out using a laboratory-made palm-top size colorimeter with a red-green-blue light-emitting diode. The reciprocal value (1/τ) of the reaction time at a fixed absorbance value for red light was chosen as a kinetic parameter for simple on-site analyses. The value of 1/τ was proportional to the concentration of manganese in the range of 2 – 20 μg L−1. At a reaction temperature (T) of 20°C or more, manganese was determined within a reaction time of 25 min. The calibration equation was approximated by 1/τ = (aT + b)[Mn] + (cT + d), where a to d were constants in a range of 10 – 40°C. The two equations for 30°C (for the laboratory-preparation of the calibration equation) and T give the value of 1/τ at 30°C as 1/τf = (30a + b)(1/τ – cTd)/(aT + b) + 30c + d. Without any temperature control, 1/τf can be calculated by this equation and measurements of 1/τ and T. The calculation introduced analytical errors of within 1 μg L−1. The proposed method was successfully applied to tap-, river- and lake-water samples.