Light scattering LALLS

A number of the limitations of conventional SEC can be overcome through use of a low angle laser light scattering (LALLS) detector attached in series with a concentration... 

Branching in the polymer chain affects the relationship between retention and molecular weight.83 Universal calibration has been used with some success in branched polymers, but there are also pitfalls. Viscosimetry84-91 and other instrumental methods have proved to be useful. A computer simulation of the effects of branching on hydrodynamic volume and the detailed effects observable in GPC is available in the literature.92 93 In copolymer analysis, retention may be different for block and random copolymers, so universal calibration may be difficult. However, a UV-VIS detector, followed by a low-angle light-scattering (LALLS) detector and a differential... 

Figure 13 Low-angle, light-scattering (LALLS) and refractive index (DRI) chromatograms for two xanthan samples. The xanthan samples were supplied by Shell (-...

The concentration of the polymer molecules eluting from SEC columns is continuously monitored by a detector. The most widely used detector in SEC is the differential reftactometer (DRI), which measures the difference in refractive index between solvent and solute. Other detectors commonly used for SEC are functional group detectors ultraviolet (UV) and infrared (IR), and absolute molecular weight detectors low angle laser light scattering (LALLS) and in-line continuous viscometers. Applications of these detectors to SEC analysis will be discussed later in the Multiple Detectors Section. Other detectors also being used are the densimeter (11-19) and the mass detector (20-23). 

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. 

This paper deals with a detailed analysis concerning the determination of M , Mw and MWD of lignins using respectively VPO, low angle laser light scattering (LALLS) and SEC. In addition, recent results obtained by on-line LALLS-SEC are presented. 

The Chromatix (14) low angle laser light scattering (LALLS)... 

Low Angle Laser Light Scattering (LALLS) results indicate, that at lower DVB/RLi molar ratios, a relatively narrow molecular weight distribution (1.04-1.1) of star-branched polymers can be synthesized. In contrast, DVB/RLi ratios greater than 11 can lead to rather broad molecular weight distributions (Mw/Mn = 1.3). 

Molar mass versus generation low-angle laser light scattering (LALLS) chemical ionization, fast atom bombardment, laser desorption and electrospray mass spectroscopy vapor phase osmometry electrophoresis. 

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. 

Early instruments employed low (forward) angle laser light scattering (LALLS) but these have been replaced by multi-angle instruments. MALLS instruments use Lorenz-Mie (often referred to as Mie) theory or Fraunhofer diffraction theory. 

Different characterization techniques were performed to establish the qualities of the block polymers containing e caprolactone. They included calibrated infrared (IR) determination of CL content, in-house gel permeation chromatography (GPC), GPC with univeral calibration curve, GPC equipped with low angle laser light scattering (LALLS/GFC), and Rheovlbron measurement of the transition temperatures. 

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