Flow Fluctuations in GPC-Viscometry

GPC-Viscometry requires a molecular weight calibration curve, usually a "Universal calibration curve" (1) Log ([η]*M) = f (Ve). With classical GPC, using only one concentration detector, perfect coiltrol of solvent flow rate is required since molecular weights of broad polymers are calculated by cornparisoil of their sliced distributions with elution volumes of narrow standards. Data acquisition being performed as a hnction of time, this comparison can be achieved accurately only when both experiments are run at exactly the same flow rate. A small error in flow rate introduces a significant error in molecular weight because of the logarithmic scale of the calibration curve.