Testa Analytical Solutions has introduced new laser options for its HK series differential refractometer to enable precise determination of specific refractive index increment (dn/dc) at the same wavelength as the light scattering application under investigation.
Light scattering is a tried and trusted method for measuring molecular weight and therefore a widely used tool for analyzing biopolymers, polymers and proteins. Most labs combine light-scattering detectors with chromatographic techniques such as gel permeation chromatography/size-exclusion chromatography (GPC/SEC). When using a GPC/SEC system with advanced detectors knowing the exact concentration of the sample at each data slice is very important. Accurately determining the dn/dc value, which is highly wavelength dependent, is vital because it is the link that translates raw refractive index data to sample concentration.
The most accurate method of determining dn/dc is to use a stand-alone batch instrument, such the HK series differential refractometer, and to take measurements at different concentrations. While this uses more sample than on-line methods, it is not influenced by chromatographic parameters.
The HK Series differential refractometer is a flexible device that may be used in either static or dynamic mode. In static mode, the specific refractive index (dn/dc) of dissolved samples can be easily and precisely determined in just a few minutes. Beneficially, the system now offers a large number of wavelength options enabling precise matching of your light scattering detector laser operating wavelength, thereby ensuring reliable and reproducible results every time.