Determination of Manganese in Environmental Samples by UV-Vis after Cloud Point Extraction

Cloud point extraction was used with 1-(2-pyridylazo)-2-naphthol (PAN) as a pre-concentration step prior to UV-vis spectrophotometer determination of trace amounts of manganese in water samples. The process is based upon the formation of Mn(II)/PAN complexes soluble in a micellar phase composed by the non-ionic surfactant Triton X-114 (octylphenoxy polyethoxyethanol). Trace Mn(II) /PAN complexes followed by UV-vis spectrophotometer measurement. In this proposed procedure, when above its cloud point temperature, these complexes are then extracted into the surfactant-rich phase. The parameters affecting the extraction efficiency, i.e. pH of aqueous solution, concentration of the PAN, amount of the surfactant, incubation temperature, and incubation time were investigated. The calibration graph was linear in the range 15-500 ng.mL(-1) with a limit of detection (LOD) of 5 ng.ml(-1). The proposed method was successfully applied for the determination of trace manganese in various water and soil samples.