Size exclusion chromatography-differential

Nagy, D. J. and Terwilliger, D. A., Size exclusion chromatography/differential viscometry of cationic polymers, J. Liq. Chromatogr., 12, 1431, 1989. 

A number of analytical techniques such as FTIR spectroscopy,65-66 13C NMR,67,68 solid-state 13 C NMR,69 GPC or size exclusion chromatography (SEC),67-72 HPLC,73 mass spectrometric analysis,74 differential scanning calorimetry (DSC),67 75 76 and dynamic mechanical analysis (DMA)77 78 have been utilized to characterize resole syntheses and crosslinking reactions. Packed-column supercritical fluid chromatography with a negative-ion atmospheric pressure chemical ionization mass spectrometric detector has also been used to separate and characterize resoles resins.79 This section provides some examples of how these techniques are used in practical applications. 

Haney, M. A., The differential viscometer. II. On-line viscosity detector for size-exclusion chromatography, /. Appl. Polym. Sci., 30, 3037, 1985. 

Molecular weight measurements were determined by size exclusion chromatography on a high pressure liquid chromatograph equipped with a differential refracto-meter. A Waters Styragel HR 5 i column set (106 104 500 A) was employed and calibrated with PS standards. THF was used as solvent at a flow rate of 1 ml/min. 

The difference in movement rates of various compounds through a column is attributed to differential migration in HPLC. This can be related to the equilibrium distribution of different compounds such as X, Y, and Z between the stationary phase and the flowing solvent(s), or mobile phase. The speed with which each compound moves through the column (ux) is determined by the number of molecules of that compound in the moving phase, at any moment, since sample molecules do not move through the column while they are in the stationary phase. The molecules of the solvent or mobile phase move at the fastest possible rate except in size exclusion chromatography, where molecular... 

Novolac molecular weights were measured in THF at 35°C by high pressure size exclusion chromatography using a Waters Model 510 pump (flow rate=1.0 ml/min), 401 differential viscometer detector and a set of Dupont PSM 60 silanized columns. A universal calibration curve was obtained with a kit of 10 narrow molecular weight distribution, linear polystyrene standards from Toya Soda Company. Data acquisition and analysis were performed on an AT T 6312 computer using ASYST Unical 3.02 software supplied with the Viscotek instrument. 

Size exclusion chromatography (SBC) is a separation process by which molecules are fractionated by size on the basis of differential penetration into porous particulate matrices. Blution volume (Vq) of any given molecular species relative to another of different size is dependent on the pore diameter of the matrix, pore-size distribution, pore volume (Vp, interstitial volume (Vq) and column dimensions. Use of SBC to estimate molecular size is achieved by plotting the log of the molecular weight of a series of calibrants against their elution volume. Since Vg is a function of Vg and Vj, its magnitude will be dependent on the geometry of a column. 

The size exclusion chromatography for this study was done in the routine manner execept for the inclusion of an online viscosity detector called a Differential Viscometer <3> (Viscotek Corp., Porter, Texas, USAl. This instrument together with an RI concentration detector permits the calculation of intrinsic viscosities across the chromatogram. An IBM PC data system with software is also provided (5). The software acquires data from both detectors, and performs calculations of intrinsic viscosity and molecular weight distributions using the Universal Calibration Method. 

Size exclusion chromatography has been greatly enriched recently by the advent of two commercial detectors, the real-time differential viscometer (DV) and the low angle laser light scattering (LALLS) photometer. The only DV detector currently available is offered by Viscotek in Porter, TX, as the model 100. 

High Performance Size Exclusion Chromatography. SEC was carried out on polystyrene-divinylbenzene gels with porosites ranging from 100 to 104A. The solvent, THF, had a flow rate of 1 ml/min. The detector was a differential refractometer. 

Size exclusion chromatography did not differentiate lower molecular weight, extended coils from higher molecular weight, compact coils (Berth, 1988). 

Size exclusion chromatography (SEC) differs significantly from all the above because the solutes—usually macromolecules—are repelled and thus partially excluded from the stationary phase rather than being differentially attracted to the immobilized phase. Exclusion (repulsion) is induced by a porous support in which the pores are so small that macromolecules fit in awkwardly, losing entropy [11,12] (see Section 2.7). Large macromolecules fit worst of all, lose the most entropy, and are thus excluded most (see Section 2.7). This mechanism is applicable both in aqueous solutions (where the technique is sometimes called gel filtration chromatography or GFC) and in nonaqueous mobile phases (often called gel permeation chromatography or GPC). 

Conventional Size Exclusion Chromatography, SEC, was performed on a Spectra Physics apparatus with two PL gel columns (5 pm particle size, 300 mm length, one with 50 A and one with 100 A pore size) and a Styragel HR2 column (7.8mm internal diameter x 300mm length). The detection was achieved with a SP8430 differential refractometer. The tolnene was elnted at a flow rate of 0.8mL.min . 

DSC differential scanning calorimetry SEC size exclusion chromatography POM polarized optical microscopy... 

---