IMPROVED METHOD FOR ELIMINATION OF THE INTERFERENCE FROM NITRATE IONS ON OXALIC ACID IN RP-HPLC BY SOLID-PHASE EXTRACTION WITH NANOSIZED LaPO₄

Abstract

An improved method using nanosized LaPO₄ as solid-phase extractor for avoiding the interference from nitrate ions on oxalic acid in RP-HPLC was developed. Nanosized LaPO₄ possessed lower solubility and higher adsorption ability for oxalic acid than previous adsorbent. Oxalic acid could be adsorbed selectively by nanosized LaPO₄ rather than nitrate, formic acid, malic acid, lactic acid, or citric acid, so the interference from nitrate ions was eliminated, and then the oxalic acid was determined by RP-HPLC at the optimum chromatographic conditions after the solid-phase extraction procedure. The accuracy of the method was confirmed with an average recovery ranging between 97.7% and 107.3%, the relative standard deviations (RSD) were less than 3.0%. This method improved the previous work and was successfully applied to determine the oxalic acid in xylem saps of tomato.

Keywords:

• interference elimination
• nanosized LaPO₄
• oxalic acid
• RP-HPLC
• solid-phase extraction
• xylem sap

ACKNOWLEDGMENT

This work is supported by the National Programs for High Technology Research and Development of China, the Research Fund for the Doctoral Program of Higher Education, SRF for ROCS, SEM, the Foundation for Talent Recommendation Program of Nanjing Normal University, and PAPD (a project funded by the Priority Acadenic Program Development of Jiangsu Higher Education Institutions).