A Spectrophotometric method for manganese determination in water samples based on ion pair formation and dispersive liquid-liquid microextraction

Abstract

A simple, inexpensive, and highly sensitive spectrophotometric method for the determination of manganese in water samples was suggested. The method is based on the formation and dispersive liquid-liquid microextraction of a violet-coloured ion pair of Mn(II) with 1,3,3-trimethyl-2-[3-(3-methyl-3H-benzothiazol-2-ylidene)-propenyl]-3Hindolium (BTIC) in the presence of 1-nitroso-2-naphtol (HL) as ligand, and subsequent UV-VIS spectrophotometric detection. The appropriate experimental conditions for DLLME procedure were found to be: a pH of 9.5; 0.12 mmol L-1 of BTIC; extraction solvent – toluene containing 1.75 mmol L-1 of HL; disperser solvent – methanol; auxiliary solvent – tetrachloromethane. Beer’s law is obeyed in the range 0.055-0.88 mg L-1 of Mn(II). The limit of detection (LOD), calculated based on three times of the standard deviation of the blank test (n=10), was found to be 0.004 mg L-1 of Mn(II).