Viscometric detection

Brambilla, G, Carlo, P, Finollo, R., Bignone, F.A., Ledda, A. Cajelli, E. (1983) Viscometric detection of liver DNA fragmentation in rats treated with minimal doses of chemical carcinogens. Cancer Res., 43, 202-209... 

Multidetector GPC software , a PC-DOS package written by Lesec (6), was used for triple detection GPC. For data acquisition, the personal computer is connected to the 150 CV and the CMX 100 through a CEC IEEE board (Capital Equipment Corporation, Burlington, MA) and a 199 scanner multimeter (Keithley, Cleveland, OH). Molecular weights are calculated using both the LALLS detection and the viscometric detection with a combination of the classical molecular weight calibration curve and the viscosity law of the standards (6). 

Preparation of the GPC system, especially the performance of the viscometric detection and the performance of the refractometer DRI prototype ( 4), was performed by the comparison of the viscosity law obtained using the TSK narrow standards represented in Figure 2 and the one obtained with a linear broad polymer, like the polystyrene Dow 1683 (Dow Chemical,... 

SEC with viscometric detection this elegant method permits the on-line measurement of Mark-Houwink coefficients for copolymers of various architectures copolymer M measurement applying Goldwasser s formula (13) is an additional benefit. 

Viscometric detection Viscometric detector Universal calibration Easy MMD calculation, K, a for copolymers. Architecture independence No CCD information. No heterogeneous samples 8, 9 7, 10, 13... 

The solution properties of hybrid-linear dendritic polyether copolymers are investigated by SEC with coupled viscometric detection from the same authors [12]. The results obtained show that the block copolymers are able to form monomolecular and multimole-cular micelles depending on the dendrimer generation and the concentration in methanol-water (good solvent for the linear blocks). 

The opportunity to measure the dilute polymer solution viscosity in GPC came with the continuous capillary-type viscometers (single capillary or differential multicapillary detectors) coupled to the traditional chromatographic system before or after a concentration detector in series (see the entry Viscometric Detection in GPC-SEC). Because liquid continuously flows through the capillary tube, the detected pressure drop across the capillary provides the measure for the fluid viscosity according to the Poiseuille s equation for laminar flow of incompressible liquids [1], Most commercial on-line viscometers provide either relative or specific viscosities measured continuously across the entire polymer peak. These measurements produce a viscometry elution profile (chromatogram). Combined with a concentration-detector chromatogram (the concentration versus retention volume elution curve), this profile allows one to calculate the instantaneous intrinsic viscosity [17] of a polymer solution at each data point i (time slice) of a polymer distribution. Thus, if the differential refractometer is used as a concentration detector, then for each sample slice i. 

The first purpose of viscometric detection in GPC is to use a universal calibration curve. At every slice, the concentration Q is obtained through refractometric data, intrinsic viscosity [17] is obtained through refractometric and viscometric data, and hydrodynamic vol-... 

The secondary use of viscometric detection is for the determination of long-chain branching. At the same molecular weight, a long-chain branched polymer has a more compact molecular structure than the linear one consequently, it also has a smaller intrinsic viscosity. Therefore, it is eluted at a higher elution volume with a linear polymer of smaller molecular weight. That means that at a given elution volume, there is a mixture of... 

Viscometric detection in GPC-SEC is extremely useful. It allows continuous viscosity measurements, which, in turn, permits the use of a unique calibration curve for all polymers (universal calibration). In addi-... 

The first purpose of viscometric detection in GPC is to use a universal calibration curve. At every slice, the concentration C/ is obtained through refractometric data, intrinsic viscosity [r/]/ is obtained through refractometric and viscometric data, and hydrodynamic volume [rj]Mi is obtained from the universal calibration curve. It is just necessary to divide [r]]Mi by [r]]i to get Mi and obtain the couple C/M/ that is necessary to calculate the various average molecular weights, as shown at the beginning of this entry, independently of the chemical nature of the sample and the standards used for calibration. 

The secondary use of viscometric detection is for the determination of long-chain branching. At the same... 

As intrinsic viscosity is affected by long-chain branching, viscometric detection provides branching information, just by comparing polymer viscosity laws. Fig. 2a represents the viscosity-law plot of a linear polymer. 

Copolymer molar mass determinations were made by size occlusion dnomatogn hy (SEC) using viscometric detection and universal calibration and are absolute. Glass transition temperatures were determined by diffowitial scanning calorimetiy (DSC) undo nitrogo) at a heating rate of 10 °C/min. 

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