Historically, one of the most effective means of determining molar mass and size information of polymers or biopolymers- without reference to standard- is by light scattering. The ultra-sensitive, solid state photodiode detectors in a DAWN DSP laser photometer enable polymers and biopolymers to be characterizes effectively without the need for column calibration or reference standards. The DAWN’s accessible range of molar mass extends from 1000, to hundreds of millions of Daltons (g/mol).

The DAWN’s multi-angle (18 angles) geometry means that accurate molar masses can be determined-even from samples which produce low signal levels. Since each detector contributes to the molar mass calculation, the result is more precise than produced by any single or dual angle instrument. This is particularly important for low molecular weight masses where the signal may be only slightly above the background.

The quantity dn/dc, also called the “specific refractive index increment” describes how much the refractive index of a polymer solution changes with respect to the concentration of the solute. Measurement of dn/dc is essential for the subsequent analysis of the light scattering signals. Polymers with larger values of dn/dc scatter more light at the same mass than those having smaller values. Therefore, knowledge of dn/dc permits the calculation of molar masses from light scattering data. Because dn/dc changes with wavelength, it is important to measure it at the same wavelength as the light scattering apparatus.

For more info about gel permeation chromatography (GPC) please read: “GPC using THF as a solvent” on our WebPage.

Equipment

Pump: Agilent 1100Series Liquid Chromatography Pump

Stationary phase: Styragel

Columns: 300 x 8.00 mm, MZ-Gel SD plus 100Å, MZ-Gel SD plus
� � � � � � � � � � � � � � � � � � � � � � � 10E3Å, MZ-Gel SD plus 10E5Å GPC Columns

Detection: DAWN EOS, Optilab DSP and Qels

Solvent: Chloroform

Flow Rate: 1 mL/min.

Injection: manual injector with tube coiled, 100 µL

Please contact Krystyna Brzezinska (kbrzez@mrl.ucsb.edu) to schedule training. Before training starts please read MANUAL.