Quantitation of polyethylene glycol by size exclusion chromatography with charged aerosol, differential refractive index, and multi-angle light scattering detectors.

Polyethylene glycol (PEG) has found tremendous applications in pharmaceutical products and has played a critical role in PEGylated drug modalities to improve pharmacokinetic properties and biological efficacy. The characterization and quantitation of PEGs are essential to control manufacture process and drug product quality. However, the assay value of PEG could change dramatically depending on the structures of the PEG and the detection techniques used. In this study, we developed a size exclusion chromatographic (SEC) method for quantitative PEG analysis, and we systematically evaluated the performance of three online detectors with different operating principles: a charged aerosol detector (CAD), a differential refractive index (dRI) detector, and a multi-angle light scattering detector (MALS). Fourteen PEG compounds covering a wide range of molecular weight (MW, 1 - 40 kDa) and molecular architectures (linear, branched, Y-shaped and multi-arm geometries) were evaluated by these three detection techniques. Our study revealed that the dRI showed the most universal responses among all the PEGs regardless of their molecular weight or geometries. In the contrast, CAD and MALS detector showed MW-dependent and semi-universal geometry-dependent responses. Another key finding is that the relative response factor for each multi-arm PEG in the CAD and the MALS were inversely correlated, suggesting both can be applied to qualitatively assess polymers of different architectures, including the ones with subtle differences in their core structures. The comparison of the three detectors not only provides the fundamental and comprehensive understanding of PEG quantitation but also enables the process development and control of high-quality PEGs in producing PEGylated therapeutics in the pharmaceutical industry.