Analytical Sciences

High-Performance Liquid Chromatographic Determination of Oxalic Acid in Tea Using Tris(1,10-phenanthroline)- ruthenium(II) Chemiluminescence

Fengwu WU, Zhike HE * , Qingyao LUO and Yun'e ZENG

Department of Chemistry, Wuhan University, Wuhan 430072, P. R. China

The chemiluminescence (CL) of Ru(phen)₃²⁺ was applied to HPLC determination of oxalic acid, which was separated by a C₁₈ reverse-phase column with a mobile phase of 0.02 mol/l NH₄Ac, mixed with 0.25 mol/l Ru(phen)₃²⁺ and 2.0 mmol/l Ce(SO₄)₂ (0.08 mol/l H₂SO₄), and then passed through a homemade CL detector. The reaction of Ce(IV) oxidized Ru(phen)₃²⁺ and the oxalic acid emitted light. The detection limit was 6.2x10^-6 mol/l for oxalic acid at a S/N ratio of 3, the relative standard deviation for 5 replicate injections of 1x10^-3 mol/l oxalic acid standard was calculated as 5.6%, and the linear calibration range was 1x10^-5 to 4x10^-3 mol/l. The method was successfully applied to determination of oxalic acid in tea. (Keywords: Oxalic acid, chemiluminescence, Ru(phen)₃²⁺, high-performance liquid chromatography, tea)

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