1994 Volume 43 Issue 5 Pages 395-401
A new method, which is similar to a liquid membrane method, was investigated for simultaneous extraction and back-extraction using two vessels with Teflon phase separators. The absorbance of metal complexes extracted was measured by a spectrophotometer with a flow cell. PAN [1-(2-pyridylazo)-2-naphthol] was used as a ionophore because of its high sensitivity. The conditions for the separation and the determination of iron(III), cobalt(II) and nickel(II) were examined under high speed stirring (2500rpm). After extraction of iron and cobalt complexes to the chloroform phase, iron complex was back-extracted with 6 M HNO3 solution immediately. The cobalt complex remained in the organic phase. Nickel-PAN complex was partially extracted at pH 4 after 40 min by a conventional extraction-procedure, which used a separatory funnel, in spite of the slow complex formation reaction. By the present method, the excess reagent (PAN) with iron complex was back-extracted into 6 M HNO3 solution. The extraction rate for the nickel-PAN complex decreased with the extraction time. Consequently, the nickel-complex was not extracted at pH 4 into the chloroform by the present method. The nickel, iron and cobalt were separated in three phases. The cobalt complex in the chloroform was determined directly in the range of 125μg by measurement of the absorbance at 570nm. The nickel remaining in the extraction vessel and the iron in the back-extraction vessel were determined with PAN after pH adjustment.
