Green SEC/GPC – comparison of two calibrations in three different solvents

Significance of the Topic

Characterizing polymer molecular weight distribution via GPC/SEC is essential for product quality and performance. Green analytical approaches reduce solvent usage and environmental impact, meeting sustainable polymer development goals.

Objectives and Study Overview

This work evaluates polystyrene (PS) and polymethylmethacrylate (PMMA) universal calibrations using a KNAUER HPLC system with a linear GPC column in three solvents: tetrahydrofuran (THF), chloroform (CHCl3), and ethyl acetate (EtOAc). Performance is assessed with narrow PS standards to compare accuracy and solvent–column compatibility.

Methodology

Calibrations were prepared using commercial PS and PMMA kits dissolved in 1 mL of each solvent (2.25 mg/mL for PS) with butylhydroxytoluene (BHT) as a flow marker. Twelve to sixteen calibration points were recorded and fitted to a 5th-degree polynomial. Key parameters:

• Column temperature: 25 °C
• Injection volume: 20 µL (partial loop)
• Flow rate: 1 mL/min, isocratic elution
• Detection: Refractive index at 10 Hz data rate

Used Instrumentation

• AZURA P6.1L HPG high-pressure pump
• AZURA AS 6.1L autosampler
• AZURA RID 2.1L refractive index detector
• AZURA CT 2.1 column thermostat
• AppliChrom StyDiViBe linear columns (500–1.5 MDa, 8×300 mm) with matching guard columns
• ClarityChrom 8.2.3 software with SEC/GPC extension

Main Results and Discussion

PS and PMMA calibrations in THF and CHCl3 yielded high accuracy with deviations below 5% and R²=1. EtOAc calibrations for PMMA failed due to PS interactions with the StyDiViBe stationary phase, leading to deviations exceeding 39%. The linear column enabled analysis times under 15 min and reduced solvent consumption by approximately 67% compared to a three-column setup.

Benefits and Practical Applications

Implementing a single linear GPC column streamlines polymer screening, lowers analysis time, and cuts solvent use and waste. Reliable calibrations in THF and CHCl3 support quality control in polymer synthesis and product development, advancing green and sustainable analytical practices.

Future Trends and Opportunities

Further research may explore:

• Expanding compatibility with additional green solvents
• Integrating multi-detector configurations for absolute molecular weight determination
• Developing novel column chemistries to prevent polymer–stationary phase interactions
• Implementing in-line solvent recycling and automation for high-throughput screening

Conclusion

KNAUER’s HPLC–GPC system with a linear column offers rapid, accurate, and solvent-efficient universal calibrations for PS and PMMA in THF and CHCl3. EtOAc is unsuitable for PS calibrations due to stationary phase interactions. This approach promotes sustainable polymer analysis.

Reference

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