Various Analysis Techniques for Organic Acids and Examples of Their Application

Significance of the topic

Organic acids are key small molecules in metabolic pathways, pharmaceutical formulations, environmental systems, energy research and food and beverage flavor. Reliable analysis of organic acids underpins sustainable technologies, drug development, quality control and microbiome studies.

Objectives and Overview

This summary reviews advanced analytical strategies for organic acid determination, covering:

• Comparison of HPLC, LC-MS and GC(-MS) platforms
• Separation modes: reversed-phase, ion exclusion, ion exchange
• Detection approaches: UV, conductivity, MS, derivatization
• Applications in pharmaceuticals, life sciences, energy, environment and food
• Emerging workflows in comprehensive metabolomics

Methodology and Instrumentation

Analytical approaches include:

• HPLC with UV at 210 nm or electroconductivity: reversed-phase columns (Shim-pack GIST C18-AQ), ion exclusion (Fast-OA, SCR-102H) and ion exchange (IC-A3) with post-column pH buffering or suppressor modules.
• LC-MS/MS methods: direct negative ESI on SPR-H columns for ~20 acids; pre-column 3-NPH derivatization to detect short-chain fatty and keto acids with high sensitivity.
• GC-MS/MS techniques: TMS derivatization for broad TCA and sugar profiling; DMT-MM condensation for volatile C2–C6 acids; barrier discharge ionization for direct formic acid quantification.

Used Instrumentation

• UHPLC systems: Shimadzu Nexera with Shim-pack GIST, Fast-OA, SCR-102H, IC-A3, SPR-H columns
• Mass spectrometry: LCMS-8060 triple quadrupole; GCMS-TQ8040 NX
• Gas chromatography: Nexis GC-2030 with thermal desorption and BID
• Conductivity detection: suppressor (ICDS-40A) and non-suppressor modes

Main Results and Discussion

Key findings:

• Reversed-phase HPLC with UV is suitable for simple matrices but prone to co-elution at 210 nm.
• Ion exclusion with post-column pH buffering greatly enhances conductivity detection of weak acids.
• Ion exchange chromatography in suppressor and non-suppressor modes balances background conductivity and sensitivity.
• LC-MS direct negative ESI resolves common organic acids; 3-NPH derivatization extends coverage in complex biological samples.
• GC-MS/MS with TMS and DMT-MM derivatization enables high-throughput profiling of >60 metabolites including volatile organic acids.
• Application examples: pharmaceutical counter-ions, bioprocess culture medium monitoring, intestinal short-chain fatty acids, biomass conversion analytics, wastewater odor profiling, wine and coffee quality, dual-injection HPLC for sugars and acids, and metabolomic surveys detecting hundreds of compounds.

Benefits and Practical Applications

• Custom selection of separation and detection enhances selectivity, throughput and sensitivity.
• Post-column buffer and suppressors overcome high-background conductivity challenges.
• Derivatization chemistries expand analyte range and stabilize volatile acids.
• Comprehensive metabolomics platforms support system-level research and routine QA/QC.
• Dual-channel autosamplers and UHPLC columns accelerate parallel analyses in industrial labs.

Future Trends and Possibilities

Emerging directions include real-time microfluidic sensors for continuous monitoring, imaging metabolomics with ambient MS, AI-driven data mining of large metabolite sets, greener reagents and sustainable consumables, and portable field analyzers for on-site organic acid measurement.

Conclusion

Optimal organic acid analysis requires matching sample type and analytical goals to the right chromatographic mode and detection strategy. Advances in UHPLC, ion chromatography, LC-MS/MS and GC-MS/MS, combined with innovative derivatization, buffering and dual-injection workflows, enable high-performance assays across diverse fields. Continued integration of novel technologies will streamline workflows and deepen biochemical insight.

References

1. Hirao Y, Nakashima M, Takemori Y, et al. Diverse Organic Acid Analysis Techniques and Examples of Their Application. Shimadzu Application Note No. 61, 2020.
2. Shimadzu. High-Speed Analysis of Organic Acids by Shim-pack Fast-OA and pH-Buffered Conductivity Detection. Technical Report C190-0489.
3. Shimadzu. Analysis of Short-Chain Fatty Acids/Organic Acids (3-NPH Derivatives) in Fecal Specimens. Application News No. C168.
4. Shimadzu. Application for Plant Metabolome Analysis Using the GC/MS/MS Smart Metabolites Database. Technical Report C146-0356.
5. Shimadzu. Analysis of Metabolites in Rat Urine Using MRM via GC-MS/MS. Application Data Sheet No. 59.