Line narrowing quantity determination

The technique discussed in Chapter 3 of the analysis of polymers has found limited applications in the analysis of polymer additives. Wide-line NMR spectroscopy has been used [24] for the determination of the diisooctylphthalate content of PVC. The principle of the method is that the narrow-line liquid-type NMR signal of the plasticiser is easily separated from the very broad signal due to the polymer - integration of the narrow-line signal permits determination of the plasticiser. A Newport Quantity Analyser Mk 1 low-resolution instrument, equipped with a 40 ml sample assembly and digital read-out, has been used to determine 20-50% of plasticiser in PVC. 

Multiple detection applied to the SEC characterization of copolymers is attractive because it yields both CCD and MWD information. A dual detection system based on two concentration detectors, for example, RI and UV, is useful where narrow standards of the homopolymers are available and where both homopolymers obey universal calibration. However, in other copolymer systems the addition of a third detector, LALLS, can offer the advantage of on-line determination of molecular weight for each eluting species. The triple detection approach gave similar values to the dual detector approach for a model copolymer system (PS-PMMA) studied. It was also applicable to a more difficult copolymer system (PS-PEO), although it appeared that where one homopolymer was present in very small quantities, an average p value gave more consistent results than correction for pi across the distribution. 

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