IC Determination of Chromium(Ⅵ) in Natural Water with VIS-Photometric Detection

Ion chromatography was applied to the determination of Cr(Ⅵ) in natural water.Testing installation and flow diagram for the analysis was given.Water sample was filtered with 0.22 μm filtering membrane and an aliquot of 500 μL was introduced into the instrument.The protective column (IonPac AG7) and separation column (IonPac AS7) were used for separation.A mixture of 300 mmol·L-1 (NH4)2SO4 solution and 120 mmol·L-1 aq.ammonia was used as eluant passing through the columns at the flow-rate 0.25 mL·min-1 to elute Cr(Ⅵ) from the column.The eluate was mixed with the color reagent (diphenylcarbazide) solution which was introduced at the flow-rate of 0.15 mL·min-1,at the mixing cell,reacted in the reaction coil to form the colored complex and measured photometrically at the wavelength of 540 nm.Linearity range was found between 0.02-50 μg·L-1,and detection limit (3S/N) was found to be 0.010 μg·L-1.Precision was tested by analyzing a water sample for 12 determinations,value of RSD found was 1.22%.