Department of Chemistry and Biochemistry , University of Texas at Arlington , Arlington , Texas 76019-0065 , United States.
Anal Chem. 2019 Mar 5;91(5):3636-3644. doi: 10.1021/acs.analchem.8b05627. Epub 2019 Feb 21.
Alkali metals, amines and alkanolamines are separated on a poly(butadiene)-maleic acid on silica stationary phase using a carbonic acid (HCO*) eluent with and without a mineral acid. The HCO* eluent is prepared in situ by high pressure permeative introduction of gaseous CO through thin membranes supported upon a porous steel disk. The permeation flux and thus the eluent concentration is controlled by varying the applied CO pressure. This novel frit-supported membrane device tolerates much higher liquid and gas pressures than Teflon AF capillaries, permitting [HCO*] exceeding 0.53 M and attaining a pH of 3.3. Silicone was presently preferred over Teflon AF, both as planar membranes, as mechanical properties of the latter change as large amounts of CO dissolve in it. After separation, the CO can be efficiently removed via another gas permeable membrane device permitting detection of the eluting bicarbonate salt conductometrically in a background of nearly pure water. Most analytes are more sensitively detected after anion conversion to hydroxide using a standard suppressor, permitting 3-17 pmol LODs on 2 mm bore columns. The data, particularly comparisons with an HNO eluent, with or without HCO*, indicate that proton exchange alone does not account for the retention behavior; some reactive addition of HCO is involved.
碱金属、胺和烷醇胺在聚丁二烯-马来酸固定相上通过使用碳酸（HCO*）洗脱剂（有无矿物酸）进行分离。HCO洗脱剂通过将气态 CO 通过支撑在多孔钢盘上的薄膜进行高压渗透引入原位制备。通过改变施加的 CO 压力来控制渗透通量，从而控制洗脱剂浓度。这种新型的 frit 支撑膜装置比 Teflon AF 毛细管能够耐受更高的液体和气体压力，允许 [HCO]超过 0.53 M，并达到 3.3 的 pH 值。目前，硅酮比 Teflon AF 更受欢迎，两者都是平面膜，因为后者的机械性能会随着大量 CO 溶解而发生变化。分离后，CO 可以通过另一个透气膜装置有效地去除，从而可以在几乎纯水中通过电导检测法检测洗脱的碳酸氢盐盐。在使用标准抑制器将阴离子转化为氢氧化物后，大多数分析物的检测灵敏度更高，在 2 毫米内径柱上的检出限为 3-17 pmol。这些数据，特别是与 HNO 洗脱剂的比较，无论是否有 HCO*，都表明质子交换本身并不能解释保留行为；涉及 HCO 的某些反应性加成。
