Analysis of Aromatic Carboxylic Acid-Related Compounds in Whiskey

Significance of the Topic

Accurate profiling of aromatic carboxylic acids and related phenolic compounds is critical for understanding whiskey flavor development, assessing product quality and authenticity, and supporting regulatory compliance. These trace constituents contribute to sensory characteristics such as aroma, mouthfeel and color, and their quantification aids in blending decisions and detection of adulteration.

Objectives and Study Overview

The primary goal of this study was to develop a rapid, robust LC-MS method for simultaneous separation and quantification of ten key aromatic carboxylic acids and phenolic derivatives in whiskey. The targets included caffeic acid, vanillic acid, syringic acid, p-coumaric acid, vanillin, syringaldehyde, scopoletin, coniferyl aldehyde, ellagic acid and sinapaldehyde. Emphasis was placed on high selectivity, sensitivity and minimal sample preparation for routine quality control.

Used Methodology and Instrumentation

A reversed-phase LC-MS approach was optimized using the following configuration:

• Liquid chromatograph: Nexera X3 UHPLC system
• Analytical column: Shim-pack Velox Biphenyl (100 mm × 2.1 mm I.D., 2.7 µm)
• Column temperature: 40 °C; injection volume: 10 µL
• Mobile phase A: 0.1 % formic acid in water; B: 0.1 % formic acid in methanol; flow rate: 0.4 mL/min
• Gradient profile: 5 % B (0–2 min) → 25 % B (2.01–7.5 min) → 100 % B (15–16 min) → 5 % B (16.01–20 min)
• Mass spectrometer: LCMS-2050 with dual ESI/APCI ionization in negative mode
• Gas settings: nebulizing gas 2.0 L/min; drying gas 5.0 L/min; heating gas 7.0 L/min; DL temp 250 °C; desolvation temp 500 °C
• Detection: selected ion monitoring (SIM) for individual analyte m/z values

Main Results and Discussion

The biphenyl stationary phase provided strong π-π interactions, yielding sharp peaks and baseline separation of all ten compounds within a 20-minute run. SIM detection enabled selective monitoring of each compound at its characteristic m/z, minimizing matrix interferences from the complex whiskey background. The method delivered consistent retention times and reproducible peak areas, demonstrating suitability for trace-level quantification.

Benefits and Practical Applications

This LC-MS protocol offers several advantages for industrial and research laboratories:

• Fast throughput with a 20-minute cycle time
• High selectivity through biphenyl column chemistry and SIM
• Minimal sample preparation, reducing analysis time and potential loss
• Versatility for routine quality control, flavor profiling and authenticity testing

Future Trends and Potential Applications

Emerging directions include integration with high-resolution mass spectrometry for non-targeted profiling, coupling with chemometric analysis to classify whiskey origins or maturation processes, and miniaturized LC-MS platforms for online monitoring during distillation or barrel aging. The approach may also extend to other spirits and fermented beverages.

Conclusion

A reversed-phase LC-MS method using the Shim-pack Velox Biphenyl column and LCMS-2050 dual ionization system effectively separates and quantifies key aromatic acids and phenolics in whiskey. The protocol combines speed, sensitivity and robustness, making it an attractive tool for quality assurance and flavor research.

Reference

• Application News 01-00641 (JP), Shimadzu Corporation, First Edition: Sep. 2024