Separation of Organic Acids on an Agilent Polaris C18-A Column

Significance of the Topic

Analysis of organic acids such as tartaric and malic acid in food and beverages is crucial for quality control and nutritional profiling. These highly polar compounds often challenge reversed phase retention and require robust methods to ensure reliable separation.

Objectives and Study Overview

This study aimed to develop and optimize an isocratic HPLC method using a polar embedded C18 column to separate six organic acids. Two column formats were evaluated: a standard 4.6×250 mm, 5 µm column and a shorter 3.0×150 mm, 3 µm version to assess analysis time and solvent usage.

Methodology

The method employed a highly aqueous mobile phase containing 0.1 percent phosphoric acid with methanol or pure water. Key parameters included flow rates of 1.0 mL/min for the 5 µm column and 0.425 mL/min for the 3 µm column, injection volumes of 20 µL and 5 µL, column temperature at 40 C, and detection at 210 nm.

Used Instrumentation

• Agilent 1260 Infinity II LC system
• Quaternary pump, vial sampler, multicolumn thermostat with quick change valve head
• Diode array detector set at 210 nm, data acquisition at 10 Hz and 20 Hz

Results and Discussion

Both column formats achieved baseline separation of tartaric, malic, lactic, citric, succinic and fumaric acids under isocratic conditions. A beverage sample analysis confirmed citric acid presence. Ten successive injections on the 5 µm column demonstrated excellent reproducibility without retention loss. Transitioning to the 3 µm column reduced run time by 40 percent and solvent consumption by 74.5 percent while maintaining resolution.

Benefits and Practical Applications

The polar embedded C18 phase resists phase collapse in 100 percent aqueous conditions, ensuring stable retention of polar analytes. The shorter column format delivers faster turnaround and lower solvent costs, making it suitable for high throughput food testing and quality assurance laboratories.

Future Trends and Potential Applications

Emerging needs in food safety and metabolomics will drive further development of polar embedded stationary phases. Miniaturized formats and UHPLC adaptations are expected to enhance speed and sensitivity. Integration with mass spectrometry can expand applicability to complex matrices.

Conclusion

The Agilent Polaris C18-A column provides reliable, reproducible separation of key organic acids in food samples using a simple isocratic method. Upgrading to a smaller particle size column can significantly improve efficiency without compromising chromatographic performance.

Reference

1. Bidlingmeyer BA, Broske AD. The role of pore size and stationary phase composition in preventing aqueous induced retention time loss in reversed phase HPLC. Journal of Chromatographic Science. 2004;42.
2. National Standards of Food Safety GB5009.157-2016. Determination of organic acids in food.