Multiangle Light Scattering and Viscometric Detector for Size-Exclusion Chromatography

A new miniaturised Light Scattering (LS) apparatus coupled with a capillary viscometer has been developed which analyses sequentially small size fractions of eluent (1 cm$^3$). The apparatus can be used in an autonomous manner in order to obtain the weight-average molar mass ($M_{\rm w}$), the $z$-average radius of gyration ($R_{\rm g}$), the second virial coefficient ($A_2$), the intrinsic viscosity ([ $\eta$] ) and the Huggins constant ($k$) by analysing a given polymer sample at different concentrations. The device can be coupled to a standard Size-Exclusion Chromatography chain in which the detector not only provides mean values, but also the evolution of [ $\eta$] , $M_{\rm w}$ and $R_{\rm g}$. as a function of elution volume ($V_{\rm e}$). Specific calibration curves ($\log(M_{\rm w}) = f (V_{\rm e})$) can be constructed for any sample, and then be used without the combined detector. In this way the molecular weight dependence of [ $\eta$] and $R_{\rm g}$ is readily obtained. Moreover, the special design of the detector allows simple collection of fractions. A number of problems which need to be solved in order to allow an efficient use of the detector are discussed. Results on polystyrene standards illustrate the good performance of the apparatus