Water content in propylene glycol monomethyl ether (PGME)

Significance of the Topic

Propylene glycol monomethyl ether (PGME) is a versatile solvent used in surface coatings, inks, cleaning solutions, de-icing formulations and agrochemical products. Accurate and rapid water content determination in PGME is essential for quality control because moisture levels influence product stability, performance and safety during industrial processing.

Objectives and Study Overview

This application note evaluates near-infrared spectroscopy (NIRS) as a faster, cost-effective alternative to Karl Fischer titration for quantifying water content in PGME. The goal is to develop a robust NIR calibration model spanning 0.03 % to 2 % water content and to compare its performance and analysis time with the standard wet chemical method.

Methodology

Samples of 1-methoxy-2-propanol with known water concentrations (0.03 % to 2 %) were analyzed in transmission mode over the 1000–2250 nm range. Measurements were carried out at a controlled temperature of 30 °C using disposable 8 mm pathlength vials to ensure reproducibility and to eliminate cleaning steps. Spectral data acquisition and model development were performed using dedicated software.

Used Instrumentation

• OMNIS NIR Analyzer Liquid (1000–2250 nm, transmission mode)
• Disposable borosilicate vials, 8 mm pathlength
• Built-in temperature control (30 °C)
• OMNIS Software with Quant Development module

Key Results and Discussion

The NIR calibration exhibited excellent agreement with Karl Fischer reference values, achieving a correlation coefficient (R²) of 1.000. The standard error of calibration (SEC) was 0.0042 % and the standard error of cross-validation (SECV) was 0.0048 %, indicating high precision. Spectral overlay demonstrated consistent absorbance patterns corresponding to water content variations. Analysis time per sample was under 10 seconds, compared to approximately 5 minutes for Karl Fischer titration.

Benefits and Practical Applications

NIR spectroscopy offers several advantages over classical titration: no reagents are required, the method is non-destructive, per-sample running costs are minimal and throughput is significantly higher. This technique is well suited for routine quality control in industrial settings, enabling rapid on-site or in-line monitoring of moisture levels in solvent products.

Future Trends and Opportunities

Further developments may include integration of NIRS in automated production lines, expansion of calibration models to related glycol ethers and multi-component analysis combining moisture and impurity detection. Advances in compact fiber-optic probes and cloud-based model management are expected to facilitate remote monitoring and real-time process control.

Conclusion

This study confirms that NIR spectroscopy is a viable, efficient alternative to Karl Fischer titration for determining water content in propylene glycol monomethyl ether. The method delivers rapid results with high accuracy, reduces operational costs and enhances laboratory or process analytics throughput.

References

No external literature cited.