Abstract
A spectrophotometric method utilizing chitosan coprecipitation for the determination of trace iron(II) was examined with 1,10-phenanthroline (phen) and tetrabromophenolphthalein ethyl ester (TBPE). Iron(II) reacted with phen to a stable cheleting complex, [Fe(phen)3]2+. [Fe(phen)3]2+ associated with TBPE− buffered at about pH 6.5 to form the ion associate [Fe(phen)3]2+·(TBPE−)2. A chitosan solution dissolved with acetic acid was added to this solution and chitosan precipitated from the solution immediately. The ion associate [Fe(phen)3]2+·(TBPE−)2 was adsorbed onto the chitosan precipitate. After centrifugation, the supernatant solution was discarded. The chitosan precipitate was dissolved with acetic acid and sodium acetate, and iron(II) could be determined by measuring the absorbance of the solution at 606 nm, that is, the maximum absorption wavelength of TBPE without any pretreatment. The detection limit (S/N = 3) was about 8 ppb. The relative standard deviations (n = 3) for 60 ppb iron(II) was 3.9%. This method is simple for the determination of iron(II) at less than 60 ppb, and there is no use of toxic organic solvents.
