Detection of diethylene glycol adulteration in propylene glycol--method validation through a multi-instrument...

Area of Science:

• Analytical Chemistry
• Chemometrics
• Spectroscopy

Background:

• Diethylene glycol (DEG) contamination in propylene glycol (PG) poses a risk.
• Economically motivated adulteration (EMA) often involves DEG in PG-water mixtures.
• Rapid screening methods are needed for field analysis.

Purpose of the Study:

• To evaluate portable Near-Infrared (NIR) instruments for detecting DEG in PG-water mixtures.
• To assess the effectiveness of a PLS model and calibration transfer for field deployment.
• To determine the method's precision, detection, and quantitation limits in a collaborative study.

Main Methods:

• Four identical portable NIR instruments were programmed with a PLS model.
• Piecewise direct standardization was used for calibration transfer between instruments.
• Samples were analyzed in Pass/Fail mode with a 1% DEG threshold.
• A collaborative study with multiple analysts and sites was conducted.

Main Results:

• The method achieved standard errors less than 2% on test sets.
• A 1% DEG threshold showed a low false negative rate (1/500).
• Collaborative study determined a limit of detection of 2.0% DEG and a limit of quantitation of 6.5% DEG.

Conclusions:

• Portable NIR instruments with PLS models are suitable for rapid screening of DEG contamination.
• The developed method is sensitive enough to detect levels of DEG relevant to EMA.
• The approach demonstrates good analytical precision across multiple field laboratories.