Determination of Molecular Weights

Molecular weight determinations of ECH—EO, ECH—AGE, ECH—EO—AGE, ECH—PO—AGE, and PO—AGE have not been reported. Some solution studies have been done on poly(propylene oxide), and these may approximate solution behavior of the PO—AGE copolymer (33,34). 

Sepharose (e.g. Sepharose CL and Bio-Gel A) is a bead form of agarose gel which is useful for the fractionation of high molecular weight substances, for molecular weight determinations of large molecules (molecular weight > 5000), and for the immobilisation of enzymes, antibodies, hormones and receptors usually for affinity chromatography applications. 

Devaux, J., Delimoy, D., Daoust, D., Legras, R., and Mercier, F. J., On the molecular weight determination of a poly(aryl-ether-ether-ketone) (PEEK ), Polymer, 26, 1994, 1985. 

Analysis of polymer additives by mass spectrometry has, for the most part, been limited to molecular weight determination of the solvent-extracted components [4,254], Field desorption is a good ionisation... 

Johnson, Y. A. Nagpal, M. Krahmer, M. T. Fox, K. F. Fox, A. Precise molecular weight determination of PCR products of the rRNA intergenic spacer region using electrospray quadrupole mass spectrometry for differentiation of B. subtilis and... 

We hope that this chapter on the molecular weight determination of synthetic polymers has illustrated that in the case of a complex polymer it is preferable to use several experimental methods for the molecular weight determination to obtain a full picture. Owing to the different sensitivity of the various methods some are blind for low molar masses while others are blind at low concentrations. As exemplified, often scaling laws can be utilized to compare results of different methods and different sensitivities. 

MOLECULAR WEIGHT DETERMINATION OF POLY(DIMETHYL SILOXANE) COPOLYMERS VIA GEL PERMEATION CHROMATOGRAPHY... 

The most rigorous evidence that proteins had defined structures was probably the molecular weight determinations of Adair and Svedberg. From 1900, however the crystallization of increasing numbers of proteins, while not a very reliable indication of purity, suggested to Schulz that proteins were not colloidal aggregates but large molecules with definite structures. 

Electrospray Ionization Mass Spectrometry - Fundamentals, Instrumentation and Applications 1st ed. Dole, R.B., editor John Wiley Sons Chichester, 1997. Fenn, J.B. Electrospray Wings for Molecular Elephants (Nobel Lecture). Angew. Chem., Int. Ed. 2003, 42, 3871-3894. Fuerstenau, S.D. Benner, W.H. Molecular Weight Determination of Megadalton DNA Electrospray Ions Using Charge Detection Time-of-Flight-MS. Rapid Commun. Mass Spectrom. 1995, 9, 1528-1538. 

There are a number of mass spectrometry techniques available and directly applicable to polymers. Since high polymers have high molecular weights, determination of unbroken chains is not usual. Even so, determination of structures of ion fragments of segments of the polymers is straightforward and a valuable tool in determining the unit structure. 

Fractionation of proteins according to size utilizing cross-linked dextran or polyacrylamide gel columns was first demonstrated by Porath and Flodin 63 in 1959. This technique has become the most widely accepted method for separation and molecular weight determination of hydrophilic and some hydrophobic macromolecules using aqueous buffers with or without organic modifier. While this technique might not be unique in its ability to resolve and separate proteins, it is one additional simple and effective tool in the chemist s armamentarium. The theories behind size-exclusion HPLC and size-exclusion chromatography at low pressure are identical and are described in several publications. 31 34 36 39 44 64 65 ... 

The objective of this present work was to investigate the feasibility of using GPC/DV for absolute molecular weight determination of hydroxypropylated lignins. In order to verify the validity of the universal calibration method, vapor phase osmometry (VPO) was used to provide reference number average molecular weight values. Comparisons with LALLS results have also been made and will be reported in another publication. 

The results of the molecular weight determination of the hydroxypropy-lated lignins by VPO are shown in Table I. It may be noted that for all samples, there was about a 20% increase in apparent molecular weights between freshly prepared solutions and those tested three days later. It is postulated that such an increase was due to a time dependent association of the hydroxypropylated lignin molecules in solution. 

Solution This problem is really no different from the molecular weight determinations of unknown acids that are often conducted in general chemistry lab courses. What is important to recognize is that there is one carboxyl group per molecule or one equivalent per mole. Therefore the molecular weight of the polymer is given by... 

Figure 4. Molecular weight determination of a drinking water concentrate with Sephadex LH20. Sampling, 10 -fold concentration of drinking water before and after chlorination (L5 mg/L of CI2, Meuse River source) on XAD-4/8, elution with DMSO (neutral fraction), and subsequent gel filtration were as described in Materials and Methods. After measuring the absorbance at 263 mm, the fractions were pooled as indicated. After dilution in water, the fractions were reconcentrated on XAD-4/8, eluted with DMSO, and assayed in the Salmonella mutagenicity test (strain TA98 S9).

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