Alkane effect in the Arizona liquid systems used in countercurrent chromatography
Alkane effect in the Arizona liquid systems used in countercurrent chromatography
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DOI：
10.1007/s00216-005-0016-7
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发表时间：
2005-09-01
影响因子：
4.3
通讯作者：
Ruiz-Angel, MJ
中科院分区：
文献类型：
--
作者：
Berthod, A;Hassoun, M;Ruiz-Angel, MJ
逆流色谱（CCC）是一种使用两相液体系统的分离技术;一个液相是移动的相，另一个液相是固定相。选择合适的液体系统可能是CCC中的一个问题，因为必须同时选择“柱”和移动的相，因为第一个完全取决于第二个。开发了一系列具有不同比例溶剂的系统以便于这种选择;庚烷/乙酸乙酯/甲醇/水两相液体系统的23种变化被标记为A至Z。这一系列被证明是非常有用的，并成为流行的亚利桑那州（AZ）液体系统。然而，作者经常用己烷代替庚烷。本文用气相色谱法和卡尔·费休滴定法测定了55个由不同烷烃（戊烷、己烷、庚烷、异辛烷和环己烷）制成的亚利桑那体系的上、下相的化学组成。分离的测试混合物由五种类固醇化合物组成。当使用不同的烷烃时，发现下部相具有相似的组成，但发现上部相发生变化。将庚烷换成己烷或异辛烷在CCC色谱图中产生最小的变化，而改变溶剂的比例导致保留体积的指数变化。环己烷的高密度使液相固定相难以保留。所有亚利桑那州的系统在30分钟内达到平衡，但并不稳定：水缓慢水解乙酸乙酯（如所示的pH值的持续下降，较低的水相），特别是在水丰富的系统（早期的字母）。
Countercurrent chromatography (CCC) is a separation technique that uses a biphasic liquid system; one liquid phase is the mobile phase, the other liquid phase is the stationary phase. Selection of the appropriate liquid system can be a problem in CCC, since it is necessary to select both the "column" and the mobile phase at the same time as the first is completely dependent on the second. A range of systems with various proportions of solvents were developed to ease this choice; 23 variations of the heptane/ ethyl acetate/methanol/water biphasic liquid system were labeled A to Z. This range proved to be extremely useful and became the popular Arizona (AZ) liquid system. However, authors often replace the heptane with hexane. In this work, the chemical compositions of the upper phases and the lower phases of 55 Arizona systems made with various alkanes (pentane, hexane, heptane, isooctane and cyclohexane) were determined by gas chromatography and Karl Fischer titration. The test mixture separated consisted of five steroid compounds. The lower phases were found to have similar compositions when different alkanes were used, but the upper phases were found to change. Exchanging heptane for hexane or isooctane produced minimal changes in the CCC chromatogram, while changing the proportions of the solvents resulted in an exponential change in the retention volumes. The high density of cyclohexane made liquid stationary phase retention difficult. All Arizona systems equilibrated within 30 min, but were not stable: water slowly hydrolyzed the ethyl acetate (as shown by a continuous decrease in the pH of the lower aqueous phase), especially in the water-rich systems (early alphabet letters).