Criteria for the use of mixed solvents in gas—liquid chromatography

• Published in: Journal of Chromatography A 1975, Vol.112, p.71-79
• Main Authors: Laub, R.J., Purnell, J.H.
• Format: Article
• Language: English
• ISSN: 0021-9673
• DOI: 10.1016/S0021-9673(00)99943-6

Recent investigations have shown that, for a stationary phase composed of a binary (A + S) mixture, the infinite dilution solute partition coefficient in the mixture, K R , is given by ▪ where K 0 A(A) and K 0 R(S) represent the corresponding partition coefficients in pure A and S, respectively, and ⊘ is a volume fraction. This equation has been shown to apply to all cases quantitatively reported in the literature and applies equally to systems wherein charge transfer, hydrogen bonding or no specific interactions are postulated. The equation and its consequences also establish criteria for the analytical usefulness of mixed phases in gas-liquid chromatography (GLC). For a two-component solute mixture, no advantage is gained by employing a mixed liquid phase. For three or more components, a mixed phase may or may not be useful, depending on the α values for each solute pair with each of the pure liquid phases. For solutes and stationary phases for which the above equation is valid, it is also possible to predict the optimum composition at which the resolution of all components will be maximized. The method is described and both theoretical and practical examples are given. The procedure is so straightforward that it offers considerable possibilities for improvement in the range of solvent selectivity available in GLC.