Analysis of Fluorobenzoate Tracers by Ion Chromatography

Abstract

AbstractPentafluorobenzoic acid (PFBA), 2,6‐difluorobenzoic acid (2,6‐DFBA), and orthotrifluoromethylbenzoic acid (o‐TFMBA) are three fluorobenzoates that have recently been used as tracers to monitor soil water and solute movement in soil systems. These fluorobenzoates are typically analyzed by high‐performance liquid chromatography (HPLC) with ultraviolet (UV) detection and have reported retention times ranging between 9 and 12.5 min. Ion chromatography (IC) analysis of these fluorobenzoates using conductivity detection is possible and faster than the currently used HPLC methodology. This study demonstrates the reliability of IC for fluorobenzoate tracer analysis. Mixed and single standard solutions (0.10–25 mg L−1) of PFBA, 2,6‐DFBA, o‐TFMBA and LiBr were prepared and analyzed using IC‐conductivity detection. High resolution among all four tracers was achieved by the methodology presented. However, we found that Cl‐ interferes with o‐TFMBA analysis even at low concentrations (1.0 mg Cl‐ L−1). Retention times of o‐TFMBA, 2,6‐DFBA, and PFBA by IC analysis ranged between 1.79 and 2.62 min with a linear detection response achieved across a 0.25 to 25 mg L−1 concentration range. These results indicate that IC analysis is an accurate and expedient means of determining both single and multiple fluorobenzoate and Br‐ concentrations in soil solutions and natural waters.