Comprehensive Two-dimensional Liquid Chromatography for Determination of Polyphenols in Red Wines

Significance of the Topic

Polyphenols in red wine contribute to the organoleptic and health-related properties of wine but present a complex mixture requiring high-resolution analytical methods. Comprehensive two-dimensional liquid chromatography offers enhanced separation power for detailed profiling of such complex natural samples.

Objectives and Overview of the Study

This study aimed to develop and apply an LC×LC-PDA-MS/MS method combining a micro cyano column in the first dimension and a partially porous C18 column in the second dimension to quantify polyphenols in red wine without sample pretreatment. A key goal was to compare conventional full-in-fraction and shifted second-dimension gradient strategies to maximize peak capacity and separation space coverage.

Methodology

Sample Preparation and Reagents
Filtered red wine samples were directly injected after 0.45 μm nylon filtration. LC-MS grade solvents (water, acetonitrile) and acetic acid were used.
Chromatographic Conditions

• First dimension: Ascentis Cyano column (250 mm × 1 mm, 5 μm); flow 20 μL/min; gradient from 2% to 100% acetonitrile with 0.1% acetic acid over 100 min.
• Second dimension: Ascentis Express C18 column (30 mm × 4.6 mm, 2.7 μm); flow 2.5 mL/min; two gradient modes: full-in-fraction and shifted gradient with continuously varying organic range.
• Modulation time: 1 min.

Mass Spectrometry Conditions
Negative electrospray ionization, m/z 100–800, flow split to ~0.4 mL/min into Shimadzu LCMS-8030, with standard nebulizing, drying gas, and temperature settings.

Used Instrumentation

• Shimadzu CBM-20A system controller
• Shimadzu LC-30AD dual pumps and DGU-20A5R/DGU-20A3R degassers for both dimensions
• Shimadzu CTO-20AC column oven and SIL-30AC autosampler
• Shimadzu SPD-M30A photodiode array detector
• Shimadzu LCMS-8030 mass spectrometer
• LCxLC-Assist and ChromSquare software

Main Results and Discussion

The conventional full-in-fraction gradient yielded a practical peak capacity of 75 with peaks concentrated along the diagonal of the 2D plot. Implementation of a shifted second-dimension gradient expanded the covered separation space, reducing correlation between dimensions and increasing practical peak capacity to 216. Extracted ion chromatograms and mass spectra confirmed the identification of key polyphenols such as gallic acid, procyanidins B1 and B2, catechin, epicatechin, and quercetin.

Benefits and Practical Applications of the Method

• High resolution separation without sample pretreatment
• Enhanced peak capacity for complex matrices
• Simultaneous targeted and untargeted polyphenol profiling
• Potential for QA/QC in wine and food industry applications

Future Trends and Potential Applications

Integration of novel stationary phases and advanced mass analyzers could further improve resolution and sensitivity. Automation of gradient optimization and data processing software will facilitate broader adoption in food, pharmaceutical, and environmental analysis. Combining LC×LC with high-resolution MS and ion mobility may enable deeper metabolomic profiling.

Conclusion

A comprehensive LC×LC-PDA-MS/MS method employing a shifted second-dimension gradient significantly enhanced separation performance for red wine polyphenols. The approach offers robust, high-capacity analysis of complex natural samples.

References

No references were provided in the original document.