Fading spectrophotometric determination of trace mercury with Hg~(2+)-iodide-acridine orange-polyvinyl alcohol association system

In NaAc-HAc buffer solution at pH 3.6 and in the presence of polyvinyl alcohol,Hg2+ reacts with excess I-and acridine orange(AO) forming a stable ion-association complex 2,which makes AO fade.Accordingly,a new fading spectrophotometric method is developed for determining trace mercury.The maximum fading wavelength is at 490 nm.The fading grade is linear with the concentration of Hg2+ in the range of 0-0.8 μg/mL with the apparent molar Absorption coefficient of 9.17×104 L·mol-1·cm-1 and the detection limit of 20.7 μg/L.The method has been applied to determine mercury in river samples after enrichment and separation with thiol cotton fiber.The relative standard deviation is 1.4%-2.7 %(n=5) and recoveries are from 98 % to 101 %.