Solvent Flexibility for Size-Based Polymer Analysis Using the Advanced Polymer Chromatography (APC) System

Importance of the Topic

The ability to switch solvents rapidly and reliably is critical for polymer size exclusion chromatography (SEC) applications, where traditional gel‐based columns suffer from swelling and limited solvent compatibility. Implementing a versatile chromatographic platform reduces the number of dedicated columns, shortens equilibration times, and improves laboratory efficiency.

Objectives and Study Overview

This study evaluates the solvent flexibility of Waters Advanced Polymer Chromatography™ (APC) System and APC XT Columns packed with sub-3 µm hybrid silica particles. Performance was assessed for polymer analyses in tetrahydrofuran (THF), toluene, and N,N-dimethylformamide (DMF) with 10 mM LiCl. Key aims included demonstrating consistent elution profiles, calibration linearity, and reproducible molecular weight determinations across solvent changes.

Methodology and Instrumentation

Instrumentation and conditions:

• System: ACQUITY APC System with low-dispersion plumbing and high backpressure tolerance
• Columns: APC XT 450 Å and APC XT 125 Å (4.6 × 150 mm, 2.5 µm) used singly or in series
• Detection: Refractive index detector at 35 °C
• Mobile phases: THF, toluene, DMF (each with 10 mM LiCl)
• Flow rate: 1 mL/min; column temperature: 35 °C
• Standards: Waters Ready-Cal polystyrene kit (17.6 k to 277 k Da) at 1 mg/mL
• Sample prep: Polymer samples dissolved in matching solvents at 1 mg/mL; 20 µL injection volume
• Data processing: Empower 3 CDS

Main Results and Discussion

Comparison of elution profiles for a narrow polystyrene sample revealed minimal shifts in retention times across THF, toluene, and DMF, reflecting stable particle packing without solvent-induced swelling. Calibration curves in each solvent exhibited excellent third-order fits (R² > 0.9999).

Triplicate molecular weight measurements for the narrow dispersity polystyrene sample showed:

• Average Mw and Mn values consistent within 0.5–2.5% across solvents
• Polydispersity index (PDI) variation under 2%
• %RSD below 1% for replicate injections

The system’s robustness was further demonstrated by cycling solvents in series-connected columns: a poly(methyl methacrylate-co-ethyl acrylate) sample yielded <2% change in Mp, Mw, Mn, and PDI after sequential exposure to THF, toluene, DMF, and back to THF.

Benefits and Practical Applications

Using hybrid silica APC Columns eliminates the need for multiple solvent-specific gel columns, cutting cost and inventory. High backpressure tolerance allows fast flow rates and rapid system and column equilibration. Laboratories benefit from:

• Reduced downtime for solvent changes
• Lower capital expenditure on spare columns
• Consistent polymer characterization across diverse chemistries

Future Trends and Opportunities

Advances may include integration of ultra-high pressure operation to further accelerate runs, expansion of hybrid particle chemistries for broader solvent ranges, and coupling with multi-detector platforms (e.g., light scattering, viscometry) for comprehensive polymer profiling. Automation of solvent switching workflows could enhance throughput for high-volume QA/QC environments.

Conclusion

The Waters ACQUITY APC System with APC XT Columns demonstrates exceptional solvent flexibility for size-based polymer analysis. Hybrid silica particles maintain column integrity across THF, toluene, and DMF, delivering reproducible molecular weight data with minimal solvent-related downtime. This approach streamlines laboratory workflows, reduces costs, and supports versatile polymer characterization without sacrificing performance.