Estimation of width of narrow molecular-weight distributions by size-exclusion chromatography with concentration and light scattering detection

A new method for the estimation of the weight-to-number-average molecular-w eight ratio, (M) over bar (W)/(M) over bar (n) of polymers with a narrow mo lecular-weight distribution, approximated by log-normal distribution, is pr oposed using size-exclusion chromatography (SEC) with concentration and lig ht-scattering detectors. From experimental data, the (M) over bar (W)/(M) o ver bar (n) ratios are calculated by two procedures: one using the concentr ation and light-scattering elution curve for the polymer measured, and the other based on the concentration elution curve and calibration line for a w ide range of molecular masses. An iteration method has been developed makin g the two (M) over bar (W)/(M) over bar (n) ratios converge. The method was applied to a series of narrow molecular-weight distribution polystyrene st andards. (C) 2001 Elsevier Science B.V. All rights reserved.