Size exclusion chromatography LALLS

In the late 1970s, low-angle laser light scattering became commercially available as a detection method for size exclusion chromatography. LALLS detection provided a new dimension to SEC analysis of polymers as a result of the measurement of absolute molecular weight, not relative molecular weight. A more detailed discussion of LALLS detection for PVA follows in the next section. 

The observations and questions raised by these workers helped stimulate the experiments which are presented here. In this work, size exclusion chromatography with low angle laser light scattering detection (SEC/LALLS) was used to probe the distribution of branching functionality in multiarm macromolecules of styrene/isoprene and styrene/buta-... 

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. 

Samples from size-exclusion chromatography/low angle laser light scattering (sec/lalls). 

Homogeneity size exclusion chromatography (SEC) coupled with low-angle laser light scattering (SEC-LALLS) electron microscopy, atomic force microscopy, scanning tunnel microscopy capillary electrophoresis. 

As stated in Section 8.2.1, only limited results concerning Mw determinations of lignins with the use of LALLS photometry have been published. This radically new and sophisticated technique constitutes an improvement over other methods, such as sedimentation equilibrium and size exclusion chromatography, for the evaluation of Mw. Its low angle capability, combined with high sensitivity, small sample size, and simplified clarification procedures, allow simple and accurate determinations to be made even on lignin samples which have been considered very troublesome. Moreover, as stated in Section 8.2.2, additional difficulties, inherent lignin properties, i.e., absorbance, fluorescence and anisotropy, may also be overcome. 

A low-angle laser light scattering (LALLS) detector was developed for use in size exclusion chromatography [133] and has been used coupled with FFF [134]. The advantage of this detector is that it can, in combination with a concentration detector (refractometer, UV/VIS, or IR photometric detector), provide direct data on molar masses of the eluted sample. 

Since the initial introduction of laser diffraction instrumentation in the 1970s, many different applications to panicle si/e aniilysis have been reported. Ihese have included measurements of si/e distributions of radioactive tracer particles, ink particles used in photocopy machines, zirconia fibers, alumina particles, droplets from electronic fuel injectors, crystal growth particles, coal powders, cosmetics, soils, resins, pharmaceuticals, metal catalysts, electronic materials, phoiugraphic emulsions, organic pigments, and ceramics. About a dozen instrument companies now produce LALLS instruments. Some I.AI.LS instruments have become popular as detectors for size-exclusion chromatography. 

Most VP-based copolymers are also characterized by K value. However, the literature on molecular weights of VP copolymers is very sparse. Wu and Senak reported in 1990 (6) the absolute molecular weights of cationic copolymers of quatemized vinyl pyrrolidone and dimethylaminoethyl methacrylate by size exclusion chromatography with low-angle laser light scattering (SEC/LALLS) and SEC with universal calibration (see Table 8). The molecular weights (relative to polyethylene oxide standards) of nonionic copolymers of vinyl pyrrolidone and vinyl acetate, a nonionic terpolymer of vinyl pyrrolidone, dimethylaminoethyl methacrylate, and vinyl caprolactam, and anionic copolymers of vinyl pyrrolidone and acrylic acid were also reported in 1991 (7) by Wu et al. (see Tables 6 and 7). 

Senak, L. Wu, C.S. Malawer, E.G. Size Exclusion Chromatography of Poly (vinylpyrrolidone) II. Absolute Molecular Weight Distribution by SEC/LALLS and SEC with Universal Calibration. J. Liq. Chromatogr. Relat. Technol. 1987,10 (6), 1127. 

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