Principles of fraction collection using the Vanquish UHPLC systems

Importance of Fraction Collection

Automated fraction collection in liquid chromatography is essential for isolating target analytes, removing impurities, and ensuring reproducible downstream analyses. By translating chromatographic resolution directly into discrete sample fractions, laboratories improve purity, facilitate preparative workflows, and support quality control in pharmaceutical, biochemical, and industrial settings.

Objectives and Study Overview

This technical note examines analytical-scale fraction collection (0.5–5 mL/min) using Thermo Scientific Vanquish UHPLC systems integrated with Chromeleon CDS and dedicated fraction collectors (F and FT). It aims to identify sources of delay volume, quantify dispersion effects, optimize software and hardware parameters, and compare time-based versus peak-based collection modes using model alkylphenone mixtures.

Methodology and Instrumentation

The analytical configuration comprises:

• Vanquish Quaternary Pump F, Split Sampler FT, Column Compartment H, and Variable Wavelength Detector
• Chromeleon CDS v7.2.8 for integrated control, delay-volume calculation, and fractionation method setup
• Fraction Collector F (1.0 mm drop-former) and FT (0.4 mm drop-former with Peltier cooling) for precise fraction discharge
• Bridge capillaries (125–500 µm ID, 5 ft length) matched to flow rates to minimize dead volume and dispersion

Key software parameters include delay time/volume, peak detection thresholds and slopes, arm movement modes (Vertical vs SawVertical), collection mode (Continue vs Interrupt), and fraction vessel capacity.

Main Results and Discussion

Delay volume sources—bridge capillary, diverter valve, and drop-former—were quantified and compensated in CDS using the equation OffsetTime+DerivativeStep+PeakTrueTime+3 s. Smaller capillary IDs (125 µm) significantly reduced dispersion without exceeding detector backpressure limits. Time-based fractionation yielded clean but slightly broadened fractions due to residual dead volume, while peak-based collection improved purity at the cost of minor carry-over when drop-former volumes were not fully purged. Optimal settings involve a 0.4 mm drop-former below 2 mL/min, minimal bridge capillary length matching calculated delay, Vertical arm movement, and Continue collection mode.

Benefits and Practical Applications

Applying these guidelines delivers high-purity fractions with minimal manual intervention, enhances reproducibility, and integrates seamlessly into preparative workflows or downstream analytical protocols. Automated delay compensation and intelligent peak recognition reduce cross-contamination risks, supporting QA/QC, sample preparation, and targeted compound isolation.

Future Trends and Applications

Emerging developments include microfluidic droplet collectors, sub-second mass-directed fractionation loops, machine learning–driven peak detection, and integrated preparative-scale UHPLC systems. Advances in cooling, inert sampling interfaces, and real-time data analytics will expand fractionation capabilities to thermally sensitive or reactive compounds.

Conclusion

Effective fraction collection relies on a balanced integration of hardware design, software control, and method parameters. By optimizing capillary dimensions, minimizing delay volume, and selecting appropriate collection strategies, analysts can directly translate chromatographic resolution into high-purity fractions, streamlining both analytical and preparative workflows.

Reference

1. Gamache P. Nebulization. Charged Aerosol Detection for Liquid Chromatography and Related Separation Techniques. Wiley; 2017.
2. Steiner F, Lamotte S. Detection Limit, Peak Capacity, Resolution. The HPLC Expert: Possibilities and Limitations of Modern HPLC. Wiley-VCH; 2016.
3. Dittmann M. External Band Broadening in HPLC/UHPLC Devices. The HPLC Expert II. Wiley-VCH; 2017.