Determination of Oxalic Acid in Tea Leaves and Urine by Decolorization Spectrophotometric Method with Zirconium(IV)-ArsenazoIII Complex

A new, simple, rapid and selective method for the determination of the oxalic acid in tea leaves and urine by decolorization spectrophotometry was developed in this paper. The method was based on the reaction between zirconium (Ⅳ) and arsenazo Ⅲ to form blue-green complex with 1∶1 mole ratio in the acidity of～1.3 mol/L and arsenazo Ⅲ in the complex could be replaced quantitatively by oxalic acid,which result in a decrease at 620 nm absobance peak. Good linearity was observed over the range of 5.5×10~(-6)～1.1×10~(-4) mol/L with good reproducibility. Detection limit better than 2.30×10~(-6) mol/L of oxalic acid can be achieved.No interference from the common coexisting ions in the samples was observed.The proposed method has been applied to the determination of oxalic acid in biological samples and the recoveries for the spiked samples were 86%～108%.