Pullulan and polyethylene oxide (PEO) are widely used as calibration standards when analyzing water-soluble polymers by size exclusion chromatography (SEC). In this application, pullulan and PEO standards were analyzed by OHpak SB-806M HQ, a polymer-based aqueous SEC column, and a multi-angle light scattering detector (SEC/MALS). Figures 1 and 2 show chromatograms obtained with a refractive index (RI) detector and the measurement results obtained by MALS for each sample. MALS data were processed by focusing on the region around the peak apex. Figure 1 plots molecular weight versus elution volume; the calibration curves for pullulan and PEO do not coincide. This is because differences in molecular structure results in different molecular sizes even at the same molecular weight. In contrast, Figure 2 shows the relationship between the root mean square (RMS) radius (molecular size) and elution volume. In this plot, the data points for pullulan and PEO fall on the same straight line. This indicates that both polymers are separated purely by the SEC mechanism, without any interaction with the column packing material.

Sample: 200 µL
0.02 % ~ 0.35 %

1. 1 - 7.Pullulan standards(MW: 14,000 - 1,600,000)
2. 8 - 13.Poly(ethylene oxide) standards(MW: 18,000 - 896,000)