逆流法对凝胶色谱峰加宽效应的研究

在以无孔玻璃珠为填料的色谱柱上研究了流动相中的分离能力和峰加宽效应。得到一定的分离能力。根据Kelley和Billmeyer描述流动相中峰加宽效应的理论,塔板高度和溶液的分子量有关而和分子量分布无关。但实验表明,对于具有相同分子量,但分子量分布不同的样品峰宽不同。苯的逆流峰加宽因子h稍大于直流峰加宽因子h′。产生这个差别的原因可以用在逆转过程中流速场受到干扰来解释。 在以多孔硅胶为填料的柱中对一系列不同分子量、分子量分布和化学结构的样品考察了逆流峰加宽因子,h,和淋出体积,Ve,之间的关系。实验表明h和Ve之间的关系具有普适性,这个结果和Tung的一致。在多孔填料柱上对苯同样得到h>h′。这个结果意味着用逆流法得到的h来校正GPC体系造成的峰加宽稍嫌不够。 只有对于分子量分布很窄的样品,其逆流淋出曲线的形状才非常接近高斯分布。

STUDY OF GPC ZONE BROADENING EFFECT BY MEANS OF REVERSE FLOW METHOD

The separation ahility and zone broadening effect in mobile phase have been studied by using GPC columns packed with nonporous glass beads. Polymer samples of different molecular weight could be separated to some extent on these columns. Kelley and Billmeyer indicated that the theoretical plate height describing zone broadening effect in mobile phase depends on the ' molecular weight of solute only. However, the width of peak was found to be different in samples of the same molecular weight but of different molecular weight distribution in the present investigation. The reverse flow zone broadening factor, h, of benzene is somewhat larger than the straight through flow zone broadening factor, h'. This may be' explaned by the fact that the velocity profile of flow was disturbed during reverse flowing.In GPC columns packed with porous silica beads the dependence of reverse flow zone broadening factor, h, on elution volume, Ve, has been examined for a series of samples of different chemical structure, different molecular weight and different molecular weight distribution. Experimental results showed that the relation between h and Ve is universal, independent of chemical structure of polymer samples in agreement with Tung's, h > h' was also found for benzene in columns with porous packing. This indicates that the use of h value obtained from the reverse flow method may lead to slight underestimation of the zone broadening effect in GPC.The shape of reverse flow elution curve was found to be very close to Gaussian only for polymer samples with narrow molecular weight distribution within the pre-meation limit of the column used.