Selectivity optimization mixture-design

Glajch, J. L., Kirkland, J. J., Squire, K. M., and Minor, J. M., Optimization of solvent strength and selectivity for reversed-phase liquid chromatography using an interactive mixture-design statistical technique, /. Chromatogr., 199, 57, 1980. 

J. Wieling, J. Schepers, J. Hempenius, C. K. Mensink, and J. H. G. Jonkman, Optimization of chromatographic selectivity of twelve sulphonamides in reversed-phase HPLC using mixture designs and multi-criteria decision making, J. Chromatogr., 545 101 (1991). 

Glajch, J.L. Kirkland, J.J. Snyder, L.R. Practical optimization of solvent selectivity in liquid-sohd chromatography using a mixture-design statistical technique. J. Chromatogr. 1982, 238, 269-280. 

Figure 4.27. Experimental design for selectivity optimization in reversed-phase chromatography by the mixture-design technique. (From ref. [375] John Wiley Sons)...

As part of their research in optimizing chromatographic methods, M.C. Breitkreitz and co-workers employed a mixture design to search for the MP composition that would give the best selectivity for a 10-component mixture separation (Breitkreitz et al., 2005). The organic solvents acetonitrile (ACN), methyl alcohol (MeOH) and tetrahydrofuran (THF) were used as water modifiers. Initially, the solvent strength of ACN in water was varied to produce a desirable separation power for all the solutes. Once this composition had been experimentally determined, the water contents of the other two solvents were predicted based on empirical relationships. In this manner, the pure components used to specify the design were, in fact, binary mixtures ACN H20, MeOH H20 and THF H20. 

Some authors have been concerned with influence of flow or diffusion on measurements of and Anderson et al. discussed diffusion of spins between compartments, characterized by different states of longitudinal magnetization, leading to diffusion-driven longitudinal relaxation. The effects were explored experimentally and analyzed quantitatively. Herold and co-workers described an on-line NMR rheometer, able to measure NMR relaxation data. The corrections required for the analysis of relaxation data measured under flow conditions were discussed. The opposite problem how to avoid the detrimental effects of unequal relaxation rates on the diffusion measurements in complex mixtures - was discussed by Barrere et Relaxation can also cause problems in other kinds of NMR experiments. Skinner and co-workers described the optimal control design of band-selective excitation pulses that accommodates both relaxation and inhomogeneity of rf fields. 

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