Polyethylene glycol (PEG) is a polyether compound derived from petroleum and is one of the most common polymer materials with various industrial biomedical applications. PEG is usually synthesized through the polymerization of ethylene oxide, where ethylene oxide reacts with ethylene glycol (EG) under the action of a catalyst to form ethylene oxide polymer. The structure of 1PEG is usually represented as H - (O-CH2-CH2) O'OH, where n represents the number of monomer units. PEG is not only soluble in water and organic solvents, but also has different physical properties based on molecular weight (MW), making it widely used in many industrial applications. More notably, it is mainly used as an excipient approved by the Food and Drug Administration (FDA) in cosmetics and pharmaceuticals. PEG can be used as a penetration enhancer, thickener, solubilizer, coating for tablets and capsules, and surface modifier in various drug delivery formulations. 2PEG has a molecular weight of 400 (PEG 400) and is a transparent, colorless, viscous liquid that can easily dissolve many hydrophobic drugs. Therefore, it is widely used as a solvent in many oral and topical drug products, especially in eye drops used to treat dry eye syndrome.

The FDA generally considers PEG safe, but depending on the synthetic route used in the polymerization process, toxic impurities such as ethylene oxide 1,4-dioxane, ethylene glycol (EG), and diethylene glycol (DG) are often encountered. Both 4.5EG and DG are considered toxic to human health and have been found to have nephrotoxicity in certain situations. In order to detect and quantify these impurities, the PEG monograph of the United States Pharmacopeia (USP) specifies the use of gas chromatography and flame ionization detection (GC-FID) as analytical methods. Specifically, the monograph stipulates the determination of EG and DG impurities based on the molecular weight (MW) of the PEG sample to be tested. This application article will focus on PEG samples with a molecular weight less than 450, and USP specifies the use of GC-FID packed columns as the analytical method. USP recommends using a stainless steel packed column with 12% G13 phase (D-sorbitol, packed on S1NS solid support), and an equivalent customized Restek packed column is used in this application.

This application article reports the results of analyzing ethylene glycol and diethylene glycol in polyethylene glycol 400 samples using a Perkin Elmer GC 2400 "system equipped with a packed column sampler and FID as a detector, in accordance with USP requirements. The results show improved productivity and optimized laboratory time. PerkinElmer Simplicity Chrom 'chromatographic data system (CDS) software manages analytical workflows and complies with 21 CFR Part 11.

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