Analysis of Organic Acid

Significance of Ion-Exclusion Analysis

Ion-exclusion chromatography with post-column conductivity detection offers a robust approach for separating and quantifying low-molecular-weight organic acids in diverse matrices. Accurate profiling of acids such as formic, acetic and lactic acid is critical in food quality control, fermentation monitoring and environmental analysis.

Objectives and Study Overview

This application note demonstrates the performance of the Shim-pack SCR-102H ion-exclusion column for simultaneous analysis of eight organic acids. The goal is to achieve baseline separation, high sensitivity and reproducibility under isocratic conditions.

Methodology and Instrumentation

The system configuration comprises:

• Analytical column: Shim-pack SCR-102H (300 mm L × 8.0 mm I.D.)
• Guard column: SCR-102H (50 mm L × 6.0 mm I.D.)
• Mobile phase: 5 mmol/L p-toluenesulfonic acid at 0.8 mL/min
• Post-column reagent: 20 mmol/L Bis-Tris with 0.1 mmol/L EDTA at 0.8 mL/min
• Column temperature: 45 °C
• Detector: Conductivity detector (CDD-10Avp)
• Injection volume: 10 µL

The dual-pump setup delivers the acidic eluent and the pH buffering reagent, enabling enhanced ion-suppression prior to detection.

Main Results and Discussion

Under these conditions, eight organic acids (phosphoric, succinic, lactic, formic, acetic, propionic, isobutyric and butyric acids at 20 mmol/L each) were resolved within a single run. Key observations include:

• Sharp, symmetrical peaks for all analytes
• Excellent retention time repeatability (RSD < 0.5%)
• Low background conductivity and stable baseline

The post-column addition of Bis-Tris/EDTA effectively suppressed ionic interferences and improved signal-to-noise ratios.

Practical Benefits and Applications

This method supports rapid quality assessment in breweries and wineries by monitoring organic acid profiles. It is also suitable for routine environmental water testing and fermentation process control. The simplicity of isocratic operation reduces maintenance and extends column life.

Future Trends and Potential Applications

Emerging applications include coupling ion-exclusion separations with mass spectrometry for structural confirmation of novel acids. Miniaturized systems and automated sample handling will further boost throughput in industrial laboratories. Integration with data analytics can enable real-time monitoring of fermentation processes.

Conclusion

The Shim-pack SCR-102H column, combined with post-column conductivity detection, delivers reproducible and sensitive analysis of common organic acids. Its ease of use and robustness make it a valuable tool for quality control and research in food, beverage and environmental laboratories.

References

• Shimadzu Corporation. Application News L516, ERAS-1000-0116, First Edition: December 2021.