Sta tionary phase

I However well the column may be coated, the stabil-I ity of the column depends on the stability of the Stas tionary phase film, and thus on the constant nature of I the surface tension forces holding it to the column wall. 8 These surface tension forces can change with tempera-I ture or be effected by the samples used for analysis. As a consequence, the surface tension can be suddenly re-i duced and the film break up. It follows that the sta-I tionary phase should be bonded in some way to the... 

Where m and r correspond to the number of solute and solvent molecules which adsorb onto the Stationary phase C (where/ " 1,2,. . . )ande,are the adsopdon energies for the solute and tte solvent molecules, respectively Hj corretponds to the M solute molecular interaction with die stationary phase while n, correqxind to the interaction of the pth solvent molecule with the stationary phase. In using this expression it is assumed that all solute/sta-tionary-phase interactions occur indqiendendy of each other. This should be true under low solute concentrations. The entropy factor of this system is represented by TS. 

One major drawback to soap chromatography is the slow rate of mass transfer across the micellar interface. Poor wetting of the reversed-phase support by an aqueous mobile phase also slows mass transfer at the mobile phase/sta-tionary phase interface and, hence, reduces column efficiency. It has been recently shown that adding an appropriate organic modifier - 1-propanol, for example - to the mobile aqueous phase in as low a concentration as 3% greatly enhances the mass transfer and increases column efficiency to a level comparable to that attained with adsorption chromatography (86). 

The polarity of the stationary-phase liquid can be characterized by a number of parameters. For this purpose, Rohrschneider in 1966 and subsequently McRey-nolds [10] in 1970 proposed a number of test components, representing specific interactions between groups of analytes and the stationary phases. The Kovats retention indices (see section 2.4) of the model compounds benzene, 1-butanol, 2-pentanone, nitropropane, and pyridine on different stationary phases are used to determine the McReynolds constants on these stationary phases. Based on the McReynolds constants, the GC column manufacturer Chrompack introduced the CP index in order to characterize the polarity of stationary phases. The CP index has a value of zero for the highly nonpolar phase squalane and a value of 100 for the very polar phase OV 275. The CP index facilitates the comparison of stationary phases from different manufacturers. A number of general-purpose stationary phases are given in Table 2. Other classification systems for GC sta tionary phases have recently been reviewed by Abraham et al. [llj. 

The dust removed in the flue gas scrubbing system is recycled to the combustion furnace together with the coal. A recycling system is thus achieved, in which the flow of material is only approximately quasi-sta-tionary after several cycles. As a result of dust recycling, the gas phase becomes enriched with volatile components (alkali compounds) which condense on cooling the flue gas, and a proportion of them return to the combustion furnace together with the dust. 

PC 5 Solvents A. Stationary phase formamide-methanol (1 1) mobile phase benzene-cyclohexane (1 1) satd. with formamide B. Paper treated with 2% liquid paraffin. Sta-Rf tionary phase, butyl acetate. Mobile phase, M Sorensen s buffer (pH 8) satd. with butyl acetate C. Methyl isobutyl ketone-methyl ethyl ketone (4 1), ascending D. Methyl isobutyl ketone, descending ... 

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