Chain-length-dependent impact of band broadening on the molar-mass determination of synthetic polymers via size-exclusion chromatography

⬢Band broadening in SEC leads to lower apparent molar masses of synthetic polymers.⬢Underestimation of molar masses is chain-length-dependent.⬢The effect is independent of the shape of the analyte⬢s molar-mass distribution.⬢Strategies for quantitative corrections are presented.⬢Conceptions about repeatability and reproducibility within SEC are set in context.

The impact of band-broadening (BB) on the molar-mass determination of synthetic polymers via size-exclusion chromatography (SEC) is systematically studied. BB is simulated using the exponentially modified Gaussian (EMG) model, which combines the two inherent and distinct characteristics contributing to BB in SEC: symmetric Gaussian broadening and asymmetric skewing. It is demonstrated that BB both during the measurement of the analyte itself and during the calibration process has an individual impact on molar-mass determination. In this context, particularly skewing leads to a chain-length-dependent underestimation of molar masses, with deviations of the apparent from the true ones of only a few percent for low molar masses to up to 20 % for high ones for reasonable extents of BB. The impact is shown to be independent of the shape of the analyte⬢s molar-mass distribution (MMD) and affects broad and multimodal MMDs similarly to narrow and unimodal ones. As a consequence, strategies are presented for a comprehensive quantitative correction of the observed effects, which may find their application in refined SEC software packages. The potential impact of the findings on general conceptions of repeatability and reproducibility within SEC experiments is discussed.