Analysis of low-molecular-weight water-soluble dietary fiber

Analysis of low-molecular-weight water-soluble dietary fiber using Shim-pack SUR-Na (SEC / Ligand Exchange mode)

Significance of the topic

Low-molecular-weight water-soluble dietary fibers (SDFS and related oligosaccharides and sugars) are important analytes in food composition, nutritional labeling and quality control. Reliable separation and quantification of these compounds informs product formulation, regulatory compliance and process control in the food industry. Methods that avoid derivatization and use simple mobile phases are particularly valuable for routine laboratory workflows.

Objectives and overview of the study

This application describes a chromatographic procedure for separating and characterizing low-molecular-weight water-soluble dietary fiber components using SEC / ligand exchange mode on Shim-pack SUR-Na stationary phase. The primary goals are to resolve common low-MW components (maltodextrins, maltose, glucose, glycerol) and demonstrate operational conditions suitable for routine analysis with a refractive index detector (RID). Key performance indicators are separation selectivity, repeatability and practical sample handling for food analysis.

Methodology

• Chromatographic principle: Size-exclusion chromatography combined with ligand exchange on a sodium-form resin (SUR-Na) to separate oligosaccharides and small sugars based on size and ionic interactions.
• Mobile phase: Ultrapure water (no organic modifier), which simplifies sample preparation and eliminates reagent contamination concerns for sugar analysis.
• Operating conditions: Elevated column temperature (80 °C) to reduce viscosity, improve mass transfer and sharpen peaks for small carbohydrates.
• Detection: Refractive index detector (RID), chosen for universal response to non-UV-absorbing sugars and sugar polymers.
• Sample requirements: Typical injection volume 50 µL; deionization of mobile phase using cation/anion deionization cartridges to minimize background conductivity and improve baseline stability for RID.

Used instrumentation

• LC System: Shimadzu LC-2070.
• Columns: Two Shim-pack SUR-Na columns connected in series (250 mm × 7.8 mm I.D., 8 µm each) with a Shim-pack SUR-Na(G) guard column (50 mm × 7.8 mm I.D., 8 µm).
• Deionization: Bio-Rad Micro-Guard De-Ashing Refill Cartridges for cation and anion removal.
• Vials and consumables: Shim-vial-H glass vials.
• Detector: Refractive index detector (RID).
• Operating parameters summary: Flow rate 0.5 mL/min; column temperature 80 °C; injection volume 50 µL; mobile phase water.

Main results and discussion

• Resolved peaks: The method separated four principal components assigned as (1) maltodextrins (higher MW oligomers), (2) maltose, (3) glucose, and (4) glycerol. Maltodextrins elute earliest (largest hydrodynamic volume), followed by disaccharide and monosaccharide peaks; glycerol elutes last as the smallest analyte.
• Resolution strategy: Using two SUR-Na columns in series increased effective column length and improved resolution between closely eluting sugars, while the ligand-exchange component of the stationary phase provided additional selectivity for saccharide structures.
• Baseline considerations: Deionization cartridges and high-temperature operation minimized baseline noise on the RID and reduced retention time variability associated with ionic contaminants.
• Practical performance: The water-only mobile phase simplifies method robustness and reduces chemical costs; however, RID detection imposes limitations on sensitivity and is sensitive to temperature and mobile-phase composition fluctuations.

Benefits and practical applications

• Non-derivatizing workflow: Direct injection with water mobile phase allows straightforward sample preparation for routine QC and compositional analysis of food products.
• Target use cases: Determination of low-molecular-weight soluble dietary fiber (SDFS), profiling of sugar and oligosaccharide content in syrups, beverages and processed foods, process monitoring during hydrolysis or saccharification steps, and verification of label claims.
• Scalability: The approach is compatible with conventional HPLC systems and laboratory environments where RID is standard; column configurations can be adapted (number of columns, particle size) to tune resolution vs. analysis time.

Limitations and considerations

• Detection limits: RID provides robust universal response but lower sensitivity compared with evaporative light-scattering detectors or mass spectrometry; volatile mobile phases are required for MS coupling, so direct MS detection would need method modification.
• Temperature control: RID baseline and retention reproducibility depend on strict temperature control; 80 °C operation requires appropriate column hardware and thermal equilibration.
• Column lifetime: High-temperature water and complex matrices may accelerate column fouling; guard columns and regular cartridge replacement are recommended.

Future trends and potential applications

• Detector upgrades: Coupling SUR-Na separations to more sensitive detectors (CAD, MS with appropriate mobile-phase modification) to improve sensitivity and structural confirmation of oligosaccharides.
• Method miniaturization and UHPLC: Development of shorter, smaller-particle versions of SUR-Na phases for faster analyses while retaining selectivity.
• Online sample cleanup: Integration of inline desalting or SPE to reduce matrix effects and extend column life for complex food samples.
• Standardization and validation: Wider adoption will drive development of validated protocols for regulatory reporting of SDFS content and inter-laboratory reproducibility studies.
• Data analytics: Use of chemometric tools to deconvolute overlapping oligomer distributions and support quantitative profiling in complex mixtures.

Conclusion

The described SEC/ligand-exchange method on Shim-pack SUR-Na provides a practical, non-derivatizing approach for resolving low-molecular-weight water-soluble dietary fiber components using water as mobile phase and RID detection. The two-column SUR-Na configuration and elevated temperature deliver improved resolution for common analytes (maltodextrins, maltose, glucose, glycerol). The protocol is well suited for routine food analysis and QC but may be complemented in advanced labs by more sensitive detection or miniaturized column formats for higher throughput and enhanced detection limits.

Reference

• Shimadzu Corporation. Application News 01-01055 (JP, ENG). Analysis of low-molecular-weight water-soluble dietary fiber using Shim-pack SUR-Na, First Edition: Sep. 2026. © Shimadzu Corporation, 2026.