Chemometric method to optimize chiral separation of imidazole derivatives by capillary electrophoresis

A chemometric methodology was proposed to optimize the migration time, height equivalent to a theoretical plate and separation of a mixture of a series of imidazole compounds by capillary electrophoresis. The optimization process was based on a special polynomial from 9 or 18 preliminary experiments. This method connects a general simplex method to a computer. A simplex two or three optimization-capillary electrophoresis (STO-CE) method has been developed in our laboratory. The most efficient separation was achieved with acetonitrile-phosphate buffer, pH 4.70, (5.30+94.70 (v/v)) with a beta-cyclodextrin concentration in the background electrolyte equal to 5.80 mM and a capillary temperature of 35 degrees C. Similar results were obtained using simple step-wise scanning. The higher relative difference obtained for these values with these two methods (simplex and step-wise scanning) was 5% for the beta-cyclodextrin concentration factor.     

Mobile-phase-viscosity dependence on DNA separation in slalom chromatography

Slalom chromatography (SC) is an alternative chromatographic procedure for the separation of relatively large double-stranded DNA molecules and is based on a new principle. The retardation of the DNA fragments from the cleavage of the Lambda DNA by the KpnI restriction enzyme was studied using an acetonitrile-phosphate buffer as a mobile phase with various concentrations of viscosity modifier (i.e. glycerol) and a C1 column as a stationary phase. The DNA molecule retention was accurately described over the glycerol concentration range using a model previously established. It was shown that the eluent viscosity increase enhanced the slalom chromatographic capacity to separate the DNA fragments. A connection between SC and 'hydrodynamic chromatography' processes was predicted to link the two processes in a global separation mechanism based on a non-equilibrium principle.     

Chiral discrimination ofN-(dansyl)-dl-amino acids on human serum albumin stationary phase: Effect of a mobile phase modifier

Summary The effect of perchlorate anion as mobile phase modifier on the separation factor, α, forN-(dansyl)-dl-norvaline andN-(dansyl)-dl-tryptophan on a human serum albumin (HSA) column was studied by varying the concentration,c, of the chaotropic agent and the column temperatureT. Gibbs-Helmholtz parameters Δ(ΔH) and Δ(ΔS) between thed andl enantiomers were determined from linear van't Hoff plots of lnα against 1/T. Thermodynamic results indicated that the enhancement of the separation factor observed asc was increased was enthalpically controlled owing to stereoselective H-bonding interactions. Such behavior was used to optimize the chromatographic conditions for separation ofN-(dansyl)-amino acids on HSA.