Data Interpretation for Coupled Molecular Weight Sensitive Detectors in Sec: Interdetector Transport Time

Abstract

The time required for polymer molecules to pass from one detector to another is a critical parameter for interpretation of multidetector size exclusion chromatography data. A method of utilizing numerical optimization to determine this quantity is presented. The chromatography system included a differential refractive index detector (DRI) in combination with a low-angle laser light scattering photometer (LALLS) and a differential viscometer (DV). The optimization method requires a conventional calibration curve (in terms of intrinsic viscosity rather than molecular weight if the DV detector is used) and the raw data from analysis of a broad molecular weight distribution linear homopolymer standard. A cubic polynomial and a least square cubic spline were used to fit the conventional calibration curve. In interpretation of the DV data, it was necessary to use a least square cubic spline to fit the conventional calibration curve. Results obtained are “effective” in that they intrinsically provide agreement with various molecular weight measures of the standard. Some evidence shows that they are slightly lower than estimates from experimental methods available.