Preconcentration and Determination of a Trace Amount of Manganese as Its Thenoyltrifluoroacetone Complex with Dibenzo-18-crown-6 by Means of Synergistic Extraction and Atomic Absorption Spectrometry

Abstract

A new method for the preconcentration and determination of trace amounts of manganese at the ppb-sub ppb level in natural water is described. The method is based on the formation of the thenoyltrifluoroacetone (TTA) complex with dibenzo-18-crown-6 (DB18C6) by means of synergistic extraction and back extraction combined with atomic absorption spectrometry. The effect of various factors (pH, shaking time, preconcentration factor and foreign ions etc.) on the extraction and back extraction of manganese has been investigated. The manganese TTA chelate in o-dichlorobenzene forms stable adducts with DB18C6 [Mn(TTA)₂•nDB18C6, n=1-2]; the stability constants (β_n) of the adducts were determined by a curve-fitting method as log β₁=4.43 and log β₂=6.85. The amount of manganese in Sai river (Kanazawa City) and Asano river (Kanazawa City) was found to be 2.4±0.3 and 12.2±0.8ng/ml, respectively.