Improved Titrimetric Analysis of Formate/Formic Acid and Comparison with Ion Chromatography and Nuclear Magnetic Resonance Spectroscopy

Abstract

The advancements in renewable energy technologies brought about a significant interest in developing formic acid based chemical and electrochemical processes. These include the electroreduction of carbon dioxide to produce formic acid or direct electrooxidation of formic acid to generate electricity in a fuel cell. Considering the neutral to alkaline nature of electrolytes used in many of these processes, formic acid usually exists as a formate species. Unlike oxalate salt, the direct titration to quantify formate molarity using potassium permanganate (KMnO₄) is difficult due to the formation of a suspended colored complex, which poses challenges in identifying the endpoint. Herein, we report two simple and efficient methods for formate and formic acid analysis, by back titration (FBT) using oxalate and iodine, respectively. These methods were shown to have an accuracy of more than 97% at a reduced cost when benchmarked against either nuclear magnetic resonance (NMR) spectroscopy or ion chromatography (IC). The effect of the analyte medium and optimization of the analytical procedure were also investigated. The formate quantification was found to vary insignificantly when different media, such as water, potassium hydroxide, potassium bicarbonate, or potassium sulfate, were used. This signifies the robustness and broader applicability of the FBT methods. Regarding the analytical steps, selecting the appropriate temperature, time, and molar ratio of participating species allowed the quantification of formate or formic acid with accuracy and precision. The analytical methods thus developed can provide alternative, cost-effective solutions for determining formate concentration for the research and development sector and for on-site analysis in industrial settings, where maintaining NMR and IC equipment may not be feasible.

Keywords:

• Back-titration
• formate analysis
• formic acid analysis
• titrimetry

Acknowledgments

The authors gratefully acknowledge funding support from Mitacs and Agora Energy Technologies, Canada.

Authors contributions

Shahid M. Bashir: Conceptualization, Investigation, Methodology and data acquisition, Formal analysis, and Writing-original draft. Muhammad Norhadif: Data acquisition. Zhicheng Xia: NMR methodology and testing. Linda Qian: IC methodology and analysis. Elod L. Gyenge: Conceptualization, Review and editing, Funding acquisition, and Supervision.

Disclosure statement

Prof. Elod Gyenge is a co-founder of Agora Energy Technologies, Vancouver, Canada.

Additional information

Funding

Agora Energy Technologies provided partial funding for this work through Mitacs Canada.