Various Analysis Techniques for Organic Acids and Examples of Their Application

Significance of the Topic

Organic acids are central to diverse fields including pharmaceutical development, food and beverage quality, environmental monitoring and the emerging bio‐energy sector. Their roles as metabolites, counter‐ions, flavor contributors or process indicators make reliable quantification and profiling of organic acids essential for research, quality control and industrial applications.

Objectives and Study Overview

This review outlines advanced separation and detection strategies for organic acids, comparing high‐performance liquid chromatography (HPLC) modes, ion chromatography, mass spectrometric approaches (LC–MS/MS, GC–MS/MS) and sampling techniques. Practical applications in pharmaceuticals, life science, energy, environment and food analysis are illustrated through case studies.

Methodology

Key analytical approaches:

• Reversed‐phase HPLC with UV detection exploiting carboxyl UV absorbance (~210 nm).
• Ion exclusion chromatography coupled to post‐column pH buffering and conductivity detection.
• Ion exchange chromatography (ion chromatography) in suppressor and non‐suppressor modes for anion analysis.
• LC–MS/MS: direct negative‐mode detection on weak‐acid columns and pre‐column derivatization (3-NPH) for short‐chain fatty acids.
• GC–MS/MS: TMS and DMT-MM derivatization schemes for volatile and semi‐volatile organic acids.
• High-throughput metabolomics combining GC–MS/MS and dual‐mode LC–MS/MS for hundreds of primary metabolites.

Used Instrumentation

Typical platforms and components:

• Shimadzu Nexera HPLC with Shim-pack GIST C18-AQ, Fast-OA and SCR-102H columns.
• UV absorbance and electrical conductivity detectors; ICDS-40A suppressor for ion chromatography (HIC-ESP systems).
• LCMS-8060 triple quadrupole MS for primary metabolites; Shim-pack SPR-H sulfonate columns.
• GCMS-TQ8040 NX and Nexis GC-2030 with barrier discharge ionization detector and thermal desorption autosampler.
• Dual injection autosampler for simultaneous organic acid and sugar profiling.
• Software packages and smart databases for automated metabolite identification and quantification.

Main Results and Discussion

• HPLC: Aqueous reversed‐phase columns enable high‐speed separation of soft drink and wine organic acids; novel stationary phases (C18-AQ) maintain retention stability under prolonged aqueous use.
• Post‐column pH buffering in ion exclusion mode enhances conductivity sensitivity by shifting organic acids to their ionic form.
• Ion chromatography suppressor mode achieves low background conductivity; non‐suppressor mode allows rapid screening of dicarboxylic acids and inorganic anions.
• LC–MS/MS direct negative‐ion detection profiles up to 21 organic acids; 3-NPH derivatization extends coverage to highly volatile short‐chain fatty acids in complex matrices (feces, culture media).
• GC–MS/MS with TMS or DMT-MM derivatization detects both volatile biofuel degradation products and key fermentation byproducts (furans, hydroxy acids).
• Application examples demonstrate counter‐ion determination in APIs, metabolic profiling of intestinal flora, screening of biomass conversion products and odor‐complaint investigations by thermal desorption GC–MS.
• Multiplatform metabolomics analyses quantify 100+ metabolites including organic acids, sugars, amino acids and nucleotides, and correlate metabolite patterns with sensory attributes (e.g., coffee bitterness).

Benefits and Practical Applications

• Tailored sensitivity and selectivity for target organic acids in diverse matrices (drugs, biofluids, wastewater, foods).
• Simultaneous multi‐compound quantification reduces analysis time and sample consumption.
• Enhanced process control in fermentation, artificial photosynthesis research and biofuel production.
• Robust quality assurance in pharmaceutical counter‐ion and impurity profiling.
• Food industry applications: flavor profiling, nutritional metabolomics, odor source identification.
• Environmental monitoring of organic acid contaminants in effluents and soil extracts.

Future Trends and Potential Applications

Advances likely to shape organic acid analysis include:

• Ultra‐high performance and multidimensional chromatography for deeper resolution of complex samples.
• Real‐time on‐line monitoring with miniaturized sensors and microfluidic platforms.
• Integrated data processing with machine learning for automated compound identification and pattern recognition.
• Expansion of non‐derivatization LC–MS methods and novel ionization techniques to widen metabolite coverage.
• Imaging metabolomics localizing organic acids in tissues and biofilms.
• Development of environmentally benign derivatization reagents and green analytical protocols.

Conclusion

Comprehensive organic acid analysis requires matching separation modes, detection methods and sample preparation to specific application needs. HPLC, ion chromatography, LC–MS and GC–MS each offer distinct advantages in sensitivity, selectivity and throughput. Emerging instrument innovations and data analytics will further enhance our ability to profile organic acids in research, industrial and regulatory environments.

References

• Hirao Y, Nakashima M, et al. Various Analysis Techniques for Organic Acids and Examples of Their Application. Shimadzu Application Note No. 61, 2020.
• Shimadzu Application News L442A. Effect of Column Temperature on Organic Acid Separation, 2019.
• Shimadzu Technical Report C190-0489. High-Speed Analysis of Organic Acids by Shim-pack Fast-OA and pH-Buffered Conductivity Detection, 2018.
• Application News C168. Analysis of Short-Chain Fatty Acids/Organic Acids (3-NPH Derivatives) in Fecal Specimens, 2019.
• Application Data Sheet 59. Analysis of Metabolites in Rat Urine Using GC–MS/MS, 2018.
• Shimadzu Application Note 48. Comprehensive Measurement of Metabolites Using GC–MS/MS and LC–MS/MS, 2020.
• Technical Report C146-0356. Application for Plant Metabolome Analysis Using the GC/MS/MS Smart Metabolites Database, 2019.