Overloading and Degradation Study in GPC Using Low Angle Laser Light Scattering Detector (LALLS)

Abstract

The unique macromolecular compression effect or delayed GPC elution of high M.W. material was observed using the GPC + LALLS technique for a polystyrene standard of M.W. 5.0 E5. Further overloading which resulted in nonlinear fractionation is also described. The degradation of a 4.2 E6 standard after elution was detected by LALLS with calculated M.W. of 1.0-1.1 E6 but not by GPC, as indicated by normal GPC retention time and the shape of the chromatogram. This degradation was further verified by reinjection of the collected fractions into the GPC which showed a bimodal distribution with calculated M.W. of ca. 1.0 E6 via GPC calibration and LALLS. The source of degradation was attributed to the 2 micron exit frit in the single Jordi mixed bed column. Similar degradation of 2.3 E6 standard to same M.W. of ca. 1.0 E6 was also observed. The use of these standards as GPC calibrants should not be affected by this “post column” degradation.