Fast Analysis of Carbohydrates in Chocolate Using Ligand-Exchange Chromatography with ELSD

Significance of the topic

Accurate analysis of carbohydrates in chocolate is critical for quality control, nutritional labeling, and process optimization in the food industry. Traditional detectors struggle with sugars due to their lack of chromophores, leading to limited sensitivity or complex sample preparation. The combination of ligand-exchange chromatography and evaporative light scattering detection (ELSD) offers a robust, sensitive method suitable for routine analysis.

Objectives and overview of the study

This application note demonstrates a fast, isocratic HPLC method for the separation and quantification of mono-, di-, and oligosaccharides in chocolate. The focus lies on determining sucrose and lactose content in four commercial chocolate samples (plain, two milk chocolates, and white chocolate) using Agilent Hi-Plex ligand-exchange columns coupled with ELSD.

Methodology and instrumentation

Sample preparation involves dissolving ground chocolate at 100 mg/mL in water and injecting 2 μL volumes. Water serves as the mobile phase, eliminating the need for buffers or organic modifiers. Separation is achieved on an Agilent Hi-Plex Pb column (7.7 × 300 mm, 8 μm particle size) at elevated temperature. The Agilent ELSD operates by nebulizing the eluent, evaporating the solvent to produce solute particles, and detecting scattered light from these particles. Key instrumentation details:

• Column: Agilent Hi-Plex Pb, 7.7 × 300 mm, 8 μm
• Detector: Agilent evaporative light scattering detector (ELSD)

Main results and discussion

Quantitative analysis reveals:

• Plain chocolate contains the highest sucrose level at approximately 69% by weight; lactose is not detected.
• Milk chocolate samples show both sucrose (30–41%) and lactose (7–17%), reflecting their milk solids content.
• White chocolate exhibits about 42% sucrose and 9% lactose.
• Chromatograms display well-resolved peaks for sugars within a short runtime, normalized to the sucrose peak for comparison.

Benefits and practical applications

The described method offers several advantages:

• High sensitivity and uniform response without the need for chromophores or high-pH environments.
• Use of water as mobile phase avoids toxic organic solvents and reduces cost and disposal issues.
• Agilent Hi-Plex columns maintain activity in sugar matrices and deliver long lifetimes compared to amino silica columns.
• Fast dissolution and isocratic operation enable high throughput in QC and research laboratories.

Future trends and possibilities for use

This approach can be extended to a broader range of food matrices, including syrups, dairy products, and confectionery. Ongoing developments may integrate sugar alcohol and organic acid analysis by selecting appropriate Hi-Plex resin forms. Coupling with automated sample handling and data processing will further enhance throughput and reliability in industrial settings.

Conclusion

The combination of ligand-exchange chromatography on Agilent Hi-Plex columns with ELSD provides a fast, sensitive, and eco-friendly method for the determination of sucrose and lactose in chocolate. Its simplicity, robustness, and low operating costs make it ideal for routine quality control and research applications.

Reference

Agilent Technologies, Inc. Fast Analysis of Carbohydrates in Chocolate Using Ligand-Exchange Chromatography with ELSD. Application Note, 2008.