New Laser Options for Accurate dn/dc Determination

The importance of light scattering in particle analysis

An important technique for measuring molecular weight, light scattering is a widely used tool for analysing 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

Differential refractometer with extended laser options

Testa Analytical Solutions eK 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.

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. 

Flexible, optimised dn/dc measurement 

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.

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