Catalytic determination of trace manganese using initial redox reaction of Malachite Green and periodate

Abstract

Malachite Green of 2.2×10⁻⁵ M and sodium periodate of 3.4×10⁻³ M were reacted at 48 °C and pH 3.3 in a cuvette of a spectrophotometer. The slight color fading at 615 nm was measured with a reference of an absorption plate of about 1.8 A, and was recorded on a strip chart as a function of time. From a tangent of the recorded linear trace, 2 to 200 ng Mn(II) was determined with a standard deviation (S. D.) of 0.5 ng within 10 min. Using the absorbance at the reaction time of 5 min, 5 to 30 ng was determined with a S. D. of 2 ng. Experimental conditions, sensitization and enhanced uncatalyzed reaction are discussed. The color fading of the wide absorbance range is also described for more than 200 ng Mn.