Data evaluation for unified multi‐detector size exclusion chromatography — molar mass, viscosity and radius of gyration distributions

Abstract

The output of a size exclusion chromatography (SEC) system was connected to a single capillary viscometer, a multi‐angle laser light scattering detector (MALLS) and a refractive index detector (RI). This provides absolute distributions of molar mass, radius of gyration and reduced viscosity, which are valuable both for practical polymer characterization and as tests of physical polymer theories. The instrument interfacing is described, along with the method of data analysis. A quantitative investigation of systematic and random sources of error and their influence on polymer characterization is made. An experimental example using a biopolyelectrolyte (hyaluronate), including complete error analysis, is presented, along with other data. Although the emphasis here is on aqueous SEC, most of the principles should carry over to organic phase SEC. A simultaneous, in‐line comparison of a low‐angle laser light scattering (LALLS) detector and MALLS detectors was also made. The dangers of ‘universal calibration’ for hydrosoluble polymers are also illustrated.

Characterization of Apple Pectin – A Chromatographic Approach

“…Theoretical slopes of 0.33, 0.50 and 1.0 occur for spheres, random coils in theta solvents, and rigid rods, respectively. Usually, most real random coils have slopes in the range 0.55-0.6 [37]; f) using a viscometer connected in series with MALLS and RI in the HPSEC system, the intrinsic viscosity can be determined [40]. HPSEC-MALLS/RI was used to compare the molar mass distribution of pectins obtained from the dried pomace of eleven apple cultivars [41].…”

Perspectivas atuais para a obtenção controlada de polímeros e sua caracterização

“…Isto pode ser facilmente resolvido com a oxidação ou hidrólise deste grupo terminal, lembrando que isso pode passar a ser uma vantagem quando o que se quer é crescer outro bloco a partir desse polímero [8] . De posse de uma tabela de concentração e massa molar (obtida pela técnica) é possível determinar a massa molar mé-dia ponderada por qualquer base, como por número ou massa, obtendo-se assim Mn (massa molar ponderada pelo número de partículas) e Mw (massa molar poderada pela massa) ao mesmo tempo e, por conseguinte, o índice de polidispersidade (Mw/Mn) [26] . Um resumo das principais características da cromatografia por exclusão de volume com multidetecção pode também ser encontrada disponível na internet [27] .…”

Real-time monitoring of enzymatic hydrolysis of galactomannans

“…It is recalled that, especially in aqueous SEC, size exclusion is often not the main mode of polymer separation. 41 The reduced amplitude of the scattering for Gase hydrolyzed Ms in figure 6a attests to the mass reduction more so, a priori, than a shift to higher elution volume).…”