A Selective Gas Chromatography–Tandem Mass Spectrometry Method for Quantitation of Ethylene and Diethylene Glycol in Paediatric Syrups

Ethylene Glycol (EG) and Diethylene Glycol (DEG) are two contaminants known to cause various human health problems. These glycols might be present in drug syrups that are based on glycerol, sorbitol, or polyethylene glycol. In late 2022, several batches of cough, antipyretics, and antihistamine syrups were reported to contain toxic levels of EG and DEG in multiple countries; this incident concerned the World Health Organization. From an analytical perspective, several methods of glycols analysis in pharmaceuticals have been reported in the literature, with the majority being dedicated to raw material analysis. This study aims to develop a selective method capable of evaluating a wide range of paediatric syrups in order to assess the safety of commercially available paediatric syrups currently distributed in the local market. This research introduces a method for determining glycols utilizing gas chromatography-tandem mass spectrometry (GC–MS/MS), which offers significantly higher selectivity than conventional single quadrupole Gas Chromatography-Mass Spectrometry (GC–MS). The developed method meets the current International Council for Harmonisation (ICH) guidelines for validation. The absence of any interfering peaks in both the unspiked sample of promethazine syrup and the reference standard solutions proved the method's selectivity. Furthermore, 2,2,2-trichloroethanol was used as an internal standard, and a new GC–MS/MS method was developed to analyze it. The calibration curves for EG and DEG were linear within the selected concentration range of 1–10 μg/mL. The detection limit for both EG and DEG was 400 ng/mL, while the quantification limit was 1 μg/mL. Recovery values for both EG and DEG met the accuracy acceptance criterion. Thus, the developed method proved to be efficient and accurate for determining EG and DEG levels in suspected contaminated syrups.