Department of Chemistry and Biochemistry, University of Texas at Arlington, 700 Planetarium Place, Arlington, TX, 76019, USA.
Millipore-Sigma, Bellefonte, PA, 16823, USA.
Anal Chim Acta. 2018 Dec 26;1042:155-164. doi: 10.1016/j.aca.2018.07.047. Epub 2018 Jul 24.
Dicationic ionic liquids (DILs) are more and more accepted as a new class of high temperature and polar stationary phases for gas chromatography (GC). This study deals with the effect of seven different fluorosulfonyl derivatized anions associated with two dications: 1,3-di(3-methylimidazolium)-2-methylpropane [2mC(mim)], and 1,3-di(3-methylimidazolium)-isobutene [i-eneC(mim)]. Thermophysical properties of the 14 synthesized DILs were evaluated in terms of melting point, viscosity, and thermal stability. The optimal physicochemical properties of 13 DILs allowed preparing 13 GC capillary columns. Accordingly, the polarity and selectivity of the DILs were evaluated by determining the Rohrschneider-McReynolds constants and the equivalent chain lengths of C18 fatty acid methyl esters (FAMEs). The symmetrical fluoroalkylsulfonyl and the trifluorosulfonate anions seem to produce the most polar DILs. Compared to classical polyethyleneglycol phases, the DILs showed substantially decreased retention of apolar compounds and a much stronger retention of the polar ones. Unique selectivities were observed with unsaturated FAMEs, polyaromatic hydrocarbons, and bacterial specific FAMEs. The two applications presented included a biodiesel and bacterial FAME analyses.
双离子液体（DILs）越来越被接受为气相色谱（GC）的一类新的高温和极性固定相。本研究涉及七种不同的氟磺酰基衍生阴离子与两个双阳离子：1,3-二（3-甲基咪唑啉）-2-甲基丙烷[2mC（mim）]和 1,3-二（3-甲基咪唑啉）-异丁烯[i-eneC（mim）]的影响。通过熔点、粘度和热稳定性来评估 14 种合成的 DIL 的热物理性质。13 种 DIL 的最佳物理化学性质允许制备 13 根 GC 毛细管柱。因此，通过测定 C18 脂肪酸甲酯（FAMEs）的 Rohrschneider-McReynolds 常数和等效链长来评估 DILs 的极性和选择性。对称氟代烷基磺酰基和三氟磺酸盐阴离子似乎产生最极性的 DILs。与经典的聚乙二醇相相比，DILs 对非极性化合物的保留显著降低，对极性化合物的保留要强得多。在不饱和 FAMEs、多环芳烃和细菌特异性 FAMEs 中观察到独特的选择性。所呈现的两个应用包括生物柴油和细菌 FAME 分析。
