Agilent G4243A 2D-LC ASM Valve Guide - Technical Note

Importance of the topic

The mismatch in solvent strength between first-dimension and second-dimension eluents in 2D-LC often causes distorted peaks, loss of resolution, and reduced sensitivity. Active Solvent Modulation (ASM) addresses this critical limitation by diluting strong 1D eluents with weak 2D solvents prior to the second-dimension column, restoring chromatographic performance and enabling reliable, high-resolution analyses.

Goals and overview

This technical note presents the design, configuration, and benefits of the Agilent G4243A 2D-LC ASM Valve solution. It outlines the operating principle of ASM, offers guidance on method development and capillary selection, and describes installation procedures to integrate ASM functionality into existing InfinityLab 2D-LC systems running 2D-LC Software A.01.04 or later.

Methodology and Instrumentation

The ASM approach relies on a dual-flow path in the 2D-LC valve head: one channel carries the sample loop content (1D solvent plus analyte), the other delivers 2D solvent through an ASM capillary. By adjusting capillary dimensions, the flow split ratio changes, achieving controlled dilution. Key components include:

• 2D-LC Valve ASM G4243A (1300 bar)
• InfinityLab 2D-LC modules and 2D-LC Software A.01.04+
• ASM capillaries (0.12 mm ID, lengths 85–680 mm) for factor adjustment
• Transfer capillaries and standard manifold connections

Method development involves:

• Selecting an appropriate ASM capillary to achieve desired dilution factor (1.5–5×)
• Setting sample-loop flush volume (recommended 3× loop volume)
• Incorporating an ASM hold phase into the 2D gradient table to accommodate dilution time
• Optimizing solvent composition during ASM and column re-equilibration for enhanced focusing

Main results and discussion

Comparative measurements of pesticide cuts illustrate the impact of ASM: conventional 2D-LC yielded broad, unresolved peaks when transferring high-organic cuts, whereas ASM-enabled runs produced sharp, well-separated signals with improved sensitivity. The calculated ASM factor, based on Hagen–Poiseuille relationships, guides capillary choice but should be fine-tuned empirically. ASM integrates seamlessly with multiple heart-cutting workflows and can be disabled for comprehensive 2D-LC modes.

Benefits and practical applications

ASM offers:

• Improved 2D resolution and peak shape for challenging solvent combinations
• Enhanced sensitivity by focusing analytes on column head
• Flexible dilution control through interchangeable capillaries
• Backward compatibility with existing G4236A valve setups

It is particularly suited for high-resolution heart-cutting applications, such as coupling HILIC in 1D with reversed-phase in 2D, pesticide screening, and complex mixture profiling.

Future trends and possibilities

Ongoing developments may include:

• Next-generation capillary materials for reduced dispersion and lower backpressure
• Automated capillary selection algorithms based on real-time pressure monitoring
• Integration with advanced detectors (e.g., high-resolution MS) for comprehensive multidimensional analysis
• Software enhancements for dynamic gradient adjustments and real-time ASM factor optimization

Conclusion

The Agilent G4243A ASM Valve provides a robust solution to solvent strength mismatch in 2D-LC. By diluting 1D eluents with weak 2D solvents via a configurable capillary split, ASM restores peak integrity, boosts resolution, and maintains efficient cycle times. Easy installation and software control make ASM a practical upgrade for laboratories seeking high-fidelity multidimensional separations.

Reference

• Agilent Technologies. Agilent G4243A 2D-LC ASM Valve Guide Technical Note, 2017.