Water content in propylene glycol monomethyl ether (PGME)

Significance of the Topic

Propylene glycol monomethyl ether (PGME) is a versatile solvent widely employed in surface coatings, printing inks, cleaning agents, deicing formulations and agrochemical applications. Accurate determination of water content in PGME is essential to ensure product performance, process efficiency and regulatory compliance.

Objectives and Study Overview

This study investigates near-infrared spectroscopy (NIRS) as a rapid, reagent-free alternative to Karl Fischer titration for quantifying water in PGME. The aim is to develop a robust calibration model that yields precise results in seconds, reducing both analysis time and operating costs.

Methodology and Instrumentation

PGME samples containing 0.03–2.0% water were analyzed in transmission mode using an OMNIS NIR Analyzer Liquid across the 1000–2250 nm range. Measurements were performed at a controlled temperature of 30 °C. Disposable glass vials with an 8 mm optical pathlength enabled straightforward sample handling without cleaning steps. Spectral acquisition and calibration model development were carried out using OMNIS software and the Quant Development module.

Used Instrumentation

• OMNIS NIR Analyzer Liquid (1000–2250 nm, temperature control 25–80 °C)
• 8 mm pathlength disposable vials and corresponding holder
• OMNIS Stand-Alone software license
• Quant Development software license for calibration modeling

Main Results and Discussion

The NIRS calibration achieved an R2 of 1.000, a standard error of calibration (SEC) of 0.0042% and a standard error of cross-validation (SECV) of 0.0048%, indicating outstanding linearity and precision. Compared to Karl Fischer titration, which requires about 5 minutes per analysis and chemical reagents, NIRS delivers immediate results without sample destruction or waste generation.

Benefits and Practical Applications

• Rapid measurements in under 10 seconds, enabling high sample throughput
• Elimination of chemical reagents and associated waste disposal
• Non-destructive analysis preserving sample integrity for further testing
• Lower operating costs and simplified laboratory workflow
• Feasible integration for inline or at-line process monitoring

Future Trends and Potential Applications

Further advances in chemometric algorithms and portable NIR sensor technology may facilitate real-time, in-process water monitoring across diverse solvent systems. Integration with automation and data analytics platforms will support enhanced quality assurance and process optimization in industrial production environments.

Conclusion

This application note demonstrates that NIRS is a reliable, fast and cost-effective method for water determination in PGME. By outperforming traditional Karl Fischer titration in speed and operational simplicity, NIRS supports high-throughput quality control and aligns with sustainability goals by eliminating reagent use.