Laser light-scattering detector

FIGURE 6.4 Comparison of Shodex GPC UT column and conventional-type column. Column Left Shodex GPC UT-806M X 2, 8 mm i.d. X 300 mm X 2. Right Conventional type column X 2, 7.8 mm i.d. X 300 mm x 2. Eluent 0.1% BHT in ODCB. Flow rate 1.0 mL/min. Detector Rl, MALLS (multi-angle laser light scattering detector). Column temp. I45°C. Sample High-density polyethylene. 

FIGURE 6.39 Hydroxyethyl cellulose. Column Left Shodex OHpak SB-806 HQ, 8.0 mm i.d. x 300 mm. Right Shodex Asahipak GF-710 HQ, 7.6 mm i.d. x 300 mm. Eluent 100 mA1 NaNOj. Flow rate 1.0 mL/min. Detector Multi-angle laser light scattering detector. Column temp. 40°C. Sample 0.05%, 200 /iL, Hydroxyethyl cellulose. 

At the moment, one recommends to determine the molecular characteristics of pectins using SEC chromatography equipped with a differential refractometer, a multiangle laser light scattering detector and a viscometer as previously described [25]. This technique needs no calibration with the usual molecular weight standards such dextrans and pullulans... 

Determined by SEC analysis using a multi-angle laser light scattering detector. 

Hammond SK, Shatkin I. 1990. The use of a laser light scattering detector to determine the mass extractable in organic solvents [Abstract]. Abs Pap Am Chem Soc 199(1-2) 123. 

Stolyhwo et al. (106) described a different analytical methodology, one that circumvents most of the problems encountered so far and permits the analysis of TGs up to and including tribehenin and the quantitative analysis of these complex mixtures with few calibrations, using a laser-light-scattering detector. For the achievement of most separations, a 250 X 4.0-mm ID HIBAR LICHROSPHER1000 CH-18/3 (5-/an particles) was used. For the achievement of some difficult separations, a second, similar column was connected online to the first one. 

The use of the laser-light-scattering detector permits the record of excellent chromatograms in gradient elution. An analysis of the test mixture of standards is shown in Fig. 37B for comparison with the same analysis obtained in isocratic conditions. The analysis lasts about 30 min before the elution of BBB instead of 18 min in isocratic conditions, but the first part of the chromatogram is considerably improved, and a number of impurities in the standards can be resolved. 

Fig. 3 GPC setup for functional group profiling. RI refractive index detector Fluorescence fluorescence detector MALLS multi-angle laser light scattering detector...

Two specialized detectors have been developed with specific applications for SEC. The first is the laser light-scattering detector, which has been around for almost 20 years but now has new electronics and computer data acquisition capabilities. Substitution of bulky He-Ne gas lasers with small, inexpensive diode lasers has greatly reduced the size and cost of laser light-scattering detectors, and the development of reference flow viscometers has provided similar size and cost advantages for viscometer detectors. 

Optical Diagram of a Low Angle Laser Light Scattering Detector Courtesy of LDC Abalytical, Thermo Instruments Corporation. 

The Multiple Angle Laser Light Scattering Detector (miniDawn ) Courtesy of Wyatt Technology Corporation... 

In addition to refractive index detectors, specialized detectors such as on-line SEC detectors and low angle laser light scattering detectors are used for determining the distribution of molecular weights by SEC. 

In the last two decades, methods for MW determination have been improved by combining two or more techniques, for instance, GPC combined with a laser light scattering detector (Fishman et al., 1986 Kontominas and Kokini, 1990) and GPC combined with sedimentation equilibrium (Harding et al., 1991). These methods not only allow absolute measurement of average MW but also provide information on the MW distribution and molecular conformations. 

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