Product News: Differential refractometer for polymer and protein analysis

26 Feb 2021


The new HK Series Differential Refractometer from Testa Analytical Solutions sets a benchmark for precise determination of specific refractive index increment (dn/dc) - an important parameter for polymer and protein molecular weight determination using light scattering techniques.

The specific refractive index increment (dn/dc) is one of the most underestimated parameters in material science. The assumption that using the approximate values for many polymers and proteins in published literature will not have a huge impact on molecular weight values determined by light scattering experiments, with or without GPC/SEC separation is incorrect. Because dn/dc is a squared term in the Debye Constant of the Zimm equation, any error in determining dn/dc will result in introducing considerable errors into molecular weight determination. In addition to this, precise determination of dn/dc within a GPC/SEC application is extremely useful in order to calculate mass-balance of the separation, and therefore determine the presence of absorption on the column which can again negatively influence any results calculated.

The HK Series dn/dc 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 new system 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.

Where the dn/dc value of the sample is already known, the HK Series dn/dc differential refractometer can be used for precise and sensitive concentration determination. The amount of sample used for this can also be easily recollected and therefore utilized for further investigations.

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