Ligand-exchange gas chromatographic separation of pyridine bases

Sol‐gel preparation and properties of Alumina adsorbents for gas separation

“…Zirconia and titania were developed to replace silica as packing materials for high-pressure liquid chromatography (HPLC) (Werber et al, 1990;Blackwell and Carr, 1991). These adsorbents were used to separate structural isomers, amino acids and proteins by HPLC (Werber and Carr, 1990;Blackwell and Carr, 1992) and to separate peridines by ligand-exchange gas chromatography (GC) (Fujimara and Ando, 1977). Sol-gel prepared alumina adsorbents have also been employed as flue-gas cleaning adsorbents and proved to be superior to the conventional adsorbents with respect to their chemical and mechanical stability (Hakvoort et al, 1987;Duisterwinkel et al, 1989).…”

Ligand-exchange gas chromatography of lower aliphatic amines on solid and liquid crystalline stationary phases

“…It is to be noted that not only the retention time of each amine but also the overall elution order and resolution are affected by the change of the concentration of ammonia in the mobile phase. These results differ significantly from those obtained on a column of zirconium phosphate of a metal-ion form, where neither the elution order nor the resolution could be changed by the change in the concentration of ligands in the mobile phase (2). The drastic effect of ammonia concentration on the separation of a mixture of mono-, di-, and tributylamines is illustrated in Figure 1.…”

“…Sorption Mechanism. During the process of conditioning of a column of copper(II) stearate coated on Chromosorb G AW/DMCS by passing the nitrogen carrier gas containing ammonia and water vapor through it, the following equilibria must be established in the column: St2Cu(NH3)4 + H20 ^St2Cu(NH3)3(H20) + NH3 (1) St2Cu(NH3)3(H20) + H20 Ŝt2Cu(NH3)2(H20)2 + NH3 (2) St2Cu(NH3)2(H20)2 + H20 Ŝt2Cu(NH3)(H20)3 + NH3 (3) St2Cu(NH3)(H20)3 + H20 ^St2Cu(H20)4 + NH3 (4) where the symbol St indicates the stearate moiety. It is very probable, however, that these reactions do not proceed virtually because the concentration of water in the mobile phase is sufficiently low and the complex-forming ability of water is much lower than that of ammonia.…”

“…Ligand-exchange chromatography is a useful technique for the separation of organic compounds having complex-forming ability, such as nitrogen-, sulfur-, oxygen-or phosphoruscontaining compounds. In ligand-exchange gas chromatography the retention of the sample compounds depends on their gas-phase basicity as well as on their steric crowdedness; i.e., the smaller the gas-phase basicity and the bulkier the substituents around the donating element, the shorter the retention time (1,2). This retention behavior is quite different from that observed in conventional partition or adsorption gas chromatography.…”