Chromatography with sub- and supercritical eluents: influence of temperature, pressure and flow-rate on the behaviour of lower alkanes

Isocratic networks in supercritical fluid chromatography

“…Studies on other mobile phases, i.e. isobutane [9], n-butane [9], propane [9], dimethyl-and diethyl ether [8], and experiments of this group on ethane, COP, N20, CHF3,and CCIF3, as well as with different modifiers and other nonpolar, reasonably volatile substrates have led to the conclusion that the general shape of the surface in the isocratic networks is at least similar. The absolute values of the k' and R , , of course, are different, depending on the nature of the mobile and the stationary phase, and the molecularweight and vapor pressure of the substrate, as well as other factors.…”

Theory and Practice of UHPLC and UHPLC–MS

“…12.1 ; Table 12.1), low cost, the nonflammability, the safety, the availability with adequate purity, the nontoxicity, the inertness toward most compounds, the miscibility to a large variety of organic solvents, and the weak UV absorbance at low wavelengths Smith, 1999;Berger, 1997). The first use of CO 2 as a supercritical mobile phase in SFC was reported by Sie et al in 1966. Although many different fluids (Table 12.1), such as light hydrocarbons (Huetz and Klesper, 1992;Lochmuller and Mink, 1990;Leyendecker et al, 1987;Wright et al, 1985;Novotny et al, 1971), MW, molecular weight; P c , critical pressure; T c , critical temperature.…”

“…xenon (Raynor et al, 1991), argon (Thurbide and Cooke, 2003), nitrous oxide (Wright et al, 1985), sulfur dioxide (Leren et al, 1991), chlorofluorocarbons (Berger and Deye, 1991b;Klesper et al, 1962), ammonia (Lauer et al, 1983), and others (Leyendecker et al, 1984) have been tested, no viable alternative has been discovered (Berger, 1997). Many of these fluids presented several drawbacks, such as safety issues, hardware damage, unsuitability for thermolabile compound analysis, and environmental pollution.…”

Comparison of eluents in supercritical fluid chromatography as based on density and free volume

“…Comparison of different mobile phases has been performed with respect to the dependence of retention and separation efficiency on temperature and pressure [l-41 as well as by means of solvatochromic shift experiments [5-71. The mobile phases investigated included ethers [ l ] , alkanes [2,3], and different low-boiling eluents [4-71. Furthermore, a comparison of pentane and carbon dioxide has been performed on the basis of the free volume [8]. The free volume, f,, was defined as the volume which exceeds Dedicated to Prof. Dr. Dr. h.c. Ernst Klesper on the occasion of his 60th birthday that required for a close packing of the molecules in the crystalline state, According to eq.…”

“…In this communication, the temperature dependence of retention with supercritical carbon dioxide and different alkane mobile phases is compared at constant density and at constant free volume, based on retention data previously published [2, 3,8,9]. Additionally, the free volume is used as a reference basis for comparing the polarity/ polarizability of different mobile phases.…”