Department of Chemistry and Polymer Science, University of Stellenbosch, Matieland, 7602, Stellenbosch, South Africa,
Anal Bioanal Chem. 2013 Oct;405(26):8607-14. doi: 10.1007/s00216-013-7252-z. Epub 2013 Aug 2.
High-temperature solvent gradient interaction chromatography (HT-SGIC) is a fast and efficient fractionation technique for the chemical composition analysis of olefin copolymers. The separation of ethylene-propylene random copolymers (EPRs) was achieved on a graphitic stationary phase, Hypercarb, at 160 °C by using linear solvent gradient elution from 1-decanol to 1,2,4-trichlorobenzene (TCB). In the present work, the solvent gradient profile was modified to improve the chromatographic separation of EPRs. With the aim to obtain a better resolution in separation, a slow increase in the volume fraction of TCB was applied. This allowed for a relatively large retention region for linear polyethylene (PE) chains on the column; thereby, a broader elution volume zone between the start of the gradient and the PE elution was achieved. The efficiency of this new gradient profile was demonstrated by analysing two fully amorphous EPR samples. Clear differences in the chemical composition of these EPR samples with similar ethylene contents have been proven by using this modified solvent gradient. The comprehensive chemical composition and microstructure analysis of the SGIC-separated fractions by FTIR revealed that ethylene/propylene (EP) copolymer chains were eluted according to their ethylene/propylene contents and E or P sequence lengths, even though they are distributed in a random manner. These results showed that the solvent composition is an important factor to affect the interactive adsorption or desorption behaviour of EP chains on Hypercarb. In this way, for the first time, the determination of the complex composition and chain structure of EPR samples was achieved within short analysis time, which is not possible till now using other fractionation techniques reported.
高温溶剂梯度相互作用色谱法（HT-SGIC）是一种快速有效的烯烃共聚物化学成分分析分离技术。在 160°C 下，通过从 1-癸醇到 1,2,4-三氯苯（TCB）的线性溶剂梯度洗脱，在石墨化固定相 Hypercarb 上实现了乙烯-丙烯无规共聚物（EPR）的分离。在本工作中，对溶剂梯度曲线进行了修改，以改善 EPR 的色谱分离。为了获得更好的分离分辨率，采用了 TCB 体积分数的缓慢增加。这使得在线性聚乙烯（PE）链在柱上具有相对较大的保留区域；从而，在梯度开始和 PE 洗脱之间实现了较宽的洗脱体积区。通过分析两个完全无定形的 EPR 样品，证明了这种新梯度曲线的效率。使用这种改进的溶剂梯度，已经证明了具有相似乙烯含量的这些 EPR 样品在化学成分上存在明显差异。通过 FTIR 对 SGIC 分离馏分的综合化学成分和微观结构分析表明，即使 EP 共聚物链以无规方式分布，它们也根据其乙烯/丙烯含量和 E 或 P 序列长度按顺序洗脱。这些结果表明，溶剂组成是影响 EP 链在 Hypercarb 上的相互吸附或解吸行为的重要因素。通过这种方式，首次在短分析时间内实现了 EPR 样品的复杂组成和链结构的测定，这是迄今为止使用其他报道的分级技术无法实现的。
