Elucidating the in vivo fate of PEG600: A rapid and oligomer-resolved analytical platform using UPC2-MS/MS with ammonium adducts

A novel ultra-performance convergence chromatography tandem mass spectrometry (UPC 2 -MS/MS) method was developed for the rapid and simultaneous quantification of nine polyethylene glycol 600 (PEG600) oligomers ( n  = 10–18) in rat plasma. This approach utilizes supercritical CO₂ as the primary mobile phase, significantly reducing organic solvent consumption and aligning with green analytical chemistry principles. A key innovation involves the selective monitoring of ammonium adducts ([M + NH₄] + ) as precursor ions, which markedly enhanced ionization efficiency and detection sensitivity. Furthermore, a post-column compensation system was integrated to mitigate ion suppression caused by the CO₂-rich mobile phase, resulting in an approximate 5- to 20-fold increase in signal response. The method achieved baseline separation of all oligomers within 3.4 min, demonstrating excellent linearity, precision (CV < 15%), accuracy (85–115%), and recovery (85–115%) in accordance with FDA guidelines. When applied to a pharmacokinetic study, the methodology successfully revealed oligomer-dependent disposition patterns, confirming its utility for in vivo fate tracing of PEG-based formulations. The environmental sustainability and practicality of the method were quantitatively assessed using Analytical GREEnness (AGREE) and Blue Applicability Grade Index (BAGI) metrics, along with the White Index algorithm, yielding high scores of 0.77, 82.5 and 76.8%, respectively. This UPC 2 -MS/MS platform offers a green, sensitive, and high-throughput analytical strategy for the oligomer-resolved characterization of PEG polymers in biological systems.