Molecular-mass calibration

Figure 26-14 Molecular mass calibration graph for polystyrene on Beckman pSpherogel molecular exclusion column (0.77 x 30 cm). Resin pore size labeled on the lines ranges from 5 nm to 100 pm. /Courtesy Anspec Co.. Ann Arbor. Ml.]...

In DNA separations the molecular mass calibration curve of a CGE system is usually described by double-logarithmic plotting of the reduced mobility i vs. molecular mass. The reduced mobility is calculated from the mobility i of the analyte in the sieving medium and that in free solution (p =plpo)-... 

Although the determination of the metal or metalloid is relatively straightforward, the complete identification of the ligand(s) presents some challenge. A systematic approach is required if the ligands are to be completely characterised. As a first step after the separation of the constituents, the column should be calibrated with compounds of known molecular mass. Calibration kits are obtainable from most manufacturers, however, if... 

The universal calibration procedure outlined by Benoit [18] offers an alternative method of establishing a molecular mass calibration for HDPE chromatograms. The procedure assumes that, in the SEC analysis, the chain molecules separate and elute according to their hydrodynamic volumes, and this in turn is directly proportional to the product of [ /] M. (see Chapter 3, section 3.2.3). 

Two types of PET were used in Overton s study [49] one polymerized in the melt, the other in the solid phase. Molecular mass calibration was achieved using both conventional polystyrene standards and PET fractions, the latter being prepared by precipitation of the polymer from a mixed solvent solution of phenol in tetrachloroethylene by progressive addition of n-hexane. Molecular masses of the fractions were determined by inherent viscosities. 

Dudley [54] has described in detail the characterization of nylon-66 by SEC. Nylon samples were initially fractionated from a mixed solvent of phenol and water, and the number average molecular weight of the fractions measured by membrane osmometry in m-cresol at 105°C. The intrinsic viscosities of the fractions were also measured, as well as their SEC in m-cresol at 130°C. The chromatograms were analysed using a molecular mass calibration based on polystyrene standards and using a g-factor for nylon-6 6 of 13.9. The Mark-Houwink equation was then determined as... 

Figure 7.5 Molecular mass calibration curve of TSKgel GMPW (a 600 x 7.5 mm I.D. colunrn) for polyethylene glycol in distilled water [15].

Buffers containing 0.1% sodium dodecyl sulphate (SDS) [3j2], 6 M guanidine hydrochloride [33] or 7M urea [34] are also used for the separation of proteins. These solvents cause denaturation of proteins. When proteins are separated in a denatured state, they are eluted almost exactly according to their molecular mass. It is therefore possible to estimate molecular masses of proteins from elution volumes by utilizing a molecular mass calibration curve established with some standards of known molecular mass. Figure 7.16 is an... 

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