Institute of Analytical Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria.
J Chromatogr A. 2010 Oct 15;1217(42):6595-8. doi: 10.1016/j.chroma.2010.07.073. Epub 2010 Aug 11.
Gradient-elution liquid chromatography (GELC) is a powerful tool for the characterization of synthetic polymers. However, gradient-elution chromatograms often suffer from breakthrough phenomena. Breakthrough can be averted by using a sample solvent as weak as the mobile phase. However, this approach is only applicable to polymers for which a sufficiently strong solvent exists which is at the same time a weak eluent. Finding such a solvent for a given polymer can be laborious or may even be impossible. Besides, when working with comprehensive two-dimensional LC the effluent of the first dimension is the injection solvent of the second dimension. In this case, it is not possible to avoid breakthrough by adjusting the eluent strength of the second-dimension injection solvent. Therefore, another strategy to avert breakthrough has to be implemented. In this work, we successfully avoided breakthrough in GELC by mixing the mobile phase not before, but after the autosampler. This was demonstrated measuring a blend of poly(methyl methacrylate) standards with different molecular-weights as model mixture with comprehensive two-dimensional GELC×size-exclusion chromatography. The strategy is thought to be applicable to all substances with a sufficiently strong dependence of retention on mobile-phase composition. This typically applies to large molecules (synthetic and natural polymers) and allows efficient refocusing. Unretained and barely retained substances are not refocused and therefore suffer in the proposed setup from peak broadening.
梯度洗脱液相色谱（GELC）是一种用于合成聚合物表征的强大工具。然而，梯度洗脱色谱图经常受到穿透现象的影响。通过使用与流动相一样弱的样品溶剂可以避免穿透。然而，这种方法仅适用于存在足够强溶剂且同时为弱洗脱剂的聚合物。为给定的聚合物找到这样的溶剂可能很费力，甚至可能不可能。此外，在使用全面二维 LC 时，第一维的流出物是第二维的进样溶剂。在这种情况下，通过调整第二维进样溶剂的洗脱强度，不可能避免穿透。因此，必须实施另一种避免穿透的策略。在这项工作中，我们通过在自动进样器后而不是在自动进样器前混合流动相，成功地避免了 GELC 中的穿透。通过使用不同分子量的聚（甲基丙烯酸甲酯）标准混合物作为模型混合物进行全面二维 GELC×尺寸排阻色谱法测量来证明这一点。该策略被认为适用于所有对流动相组成有足够强保留依赖性的物质。这通常适用于大分子（合成和天然聚合物），并允许有效的重新聚焦。未保留和几乎未保留的物质不会被重新聚焦，因此在提出的设置中它们会受到峰展宽的影响。
