Application of conventional thermodynamic approximations to mixed-solvent gas—liquid chromatography

Utility of mixed packings in gas-liquid chromatography

“…Recently, however, Laub, Purnell, and their colleagues (17)(18)(19)(20)(21)(22)(23)(24)(25)(26) have introduced a new graphical method of representation of retention data wherein separations are optimized quantitatively with respect, e.g., to binary stationary-phase composition, to column temperature, to binary mobile-phase partial pressure, or to any other property of the chromatographic system which can be utilized to alter elution behavior. In essence, their procedure requires only that retentions (i.e., partition coefficients, specific retention volumes, capacity factors, a values, retention indices, etc.)…”

“…In any event, as argued by Laub and Purnell (3), by Laub and Wellington (19), and later by Tiley (26), retentions with mixed-bed sorbents must conform to Equation 1, since the phases are thereby separated physically within the column. This feature is a major attraction of the window diagram procedure since mechanical mixtures of pure-phase packings are fabricated more easily than intimately-blended phases and since mechanically mixed packings can readily be provided in a laboratory on a routine basis.…”

“…10,19). However, recent studies by Ashworth and Hooker (21), Parcher and Westlake (22), Christian, Tucker, and Mitra (23, 24), Aeree and Bertrand (25), Tiley (26), and others have shown that the relation is in the several instances examined with intimately-blended solvents accurate to no better than 20%. Harbison, Laub, Martire, Purnell, and Williams (27) showed in fact that plots of KR(M) against 0C were indeed curved for a number of solutes with squalane and dinonyl phthalate phases at 30 °C; deviations from linearity were in all cases positive and exhibited maxima of ca.…”

Solute liquid-gas activity and partition coefficients with mixtures of n-hexadecane and n-octadecane with N,N-dibutyl-2-ethylhexylamide solvents

“…We take the nominal value of Kd to be 0.20 dm3 mol'1 whence, since for pure amide 0 = (VCi/4Kd)[-l + (1 + 8Kd/VCl)1/2l (18) we calculate that </>c, = 0.568 and, by extrapolation of KR(M) from regions of small </>c to c = 1, that E^(Cl) = 2840.…”

“…The complete mechanism is clearly very complicated, and that shown for the high-pressure situation by eq 13-24 is undoubtedly oversimplified. Nevertheless, the agreement obtained between the experimental quantum yields and those derived from the mechanism of eq [13][14][15][16][17][18][19][20][21][22][23][24], including their dependencies on pressure and intensity, suggests that the proposed mechanism is a good approximation that forms a useful framework in which to consider the vacuum ultraviolet photodecomposition of phosphine. ternary n-alkane systems (with one com-, infinite dilution), Harbison, Laub, Martire, Pur Williams13 established that it was obeyed to no , nan 9% by a range of solutes with squalane and o .yl phthalate solvents, as evidenced in addition in ti, ,• contempoary studies of Ashworth and Hooker, 14 Parcher and Westlake, 15 Christian, Tucker, and Mitra,16 and Tucker and Christian.…”