Comparison of the miniaturised techniques capillary electrochromatography and capillary liquid chromatography for the chiral separation of chlorthalidone

Preparation of perphenylcarbamoylated β-cyclodextrin-silica hybrid monolithic column with "one-pot" approach for enantioseparation by capillary liquid chromatography

Perphenylcarbamoylated β-cyclodextrin-silica (Ph-β-CD-silica) hybrid monolithic columns for enantioseparation in capillary liquid chromatography (cLC) have been prepared by a "one-pot" approach via the polycondensation of alkoxysilanes and in situ copolymerization of mono (6(A)-N-allylamino-6(A)-deoxy)-Ph-β-CD and vinyl group on the precondensed siloxanes. The morphologies of the Ph-β-CD-silica hybrid monolithic columns were characterized by optical microscopy and scanning electron microscopy (SEM), showing the uniform monolithic matrixes tightly bonded onto the capillary wall. The content of Ph-β-CD incorporated in monolithic matrix by the "one-pot" approach was ca. 2.9 times higher than that by postmodification method. The permeability of the Ph-β-CD-silica chiral hybrid monolithic column was 3.63 × 10(-14) m(2), and the minimum plate height was 12 μm corresponding to 83,300 theoretical plates/meter. Enantioseparations of 13 racemates were achieved by the Ph-β-CD-silica hybrid monolithic column. In this work, since the prepolymerization system mainly consisted of organic solvent (methanol (MeOH), N,N-dimethylformamide (DMF)), the limitation and difficulty of the use of water insoluble organic monomers in the previously reported "one-pot" method was circumvented. Therefore, various β-CD derivatives as well as other hydrophobic monomers could thus be used to prepare organic-silica hybrid monolithic columns with the "one-pot" process.

Recent accomplishments in the field of enantiomer separation by CEC

The present review intends to summarize recent developments in the field of enantioselective separations and analysis by CEC. It covers studies published in English language in common peer-reviewed journals within the period between 2003 and 2006. Both, methods making use of chiral mobile phase additives as well as chiral stationary phases for electrochromatographic enantiomer separations, are reviewed. Achievements that have been made on the various column technologies, such as open-tubular, particle-packed, inorganic, organic and particle-fixed (hybrid-type) monolithic as well as molecularly imprinted polymer phases, are discussed.

Statistical designs and response surface techniques for the optimization of chromatographic systems

This paper describes fundamentals and applications of multivariate statistical techniques for the optimization of chromatographic systems. The surface response methodologies: central composite design, Doehlert matrix and Box-Behnken design are discussed and applications of these techniques for optimization of sample preparation steps (extractions) and determination of experimental conditions for chromatographic separations are presented. The use of mixture design for optimization of mobile phases is also related. An optimization example involving a real separation process is exhaustively described. A discussion about model validation is presented. Some applications of other multivariate techniques for optimization of chromatographic methods are also summarized.

Experimental design for a basic mixture on a fluorinated packing

An optimization methodology is introduced for investigating the separation and the retention behavior of analytes on a new fluorinated reversed-phase packing. Ten basic compounds were selected as test probes to study the predictive models developed by using SPSS and MATLAB software. A two-level orthogonal array design (OAD) was used to extract significant parameters. The significant factors were optimised using a central composite design to obtain the quadratic relationship between the dependent and the independent variables. Using this strategy, response surfaces were derived as the 3D and contour plots, and mathematical models were defined for the separation. The models had a satisfactory coefficient (R(2) > 0.97, n = 16). For the test compounds, the best separation condition was: MeCN/30 mM phosphate buffer pH 7.1(55.5:44.5, v/v) and 10 basic solutes were resolved in 22 min. The significant influence of the concentration of buffer shows that different mechanisms of separation for basic compounds on the fluorinated packing exist compared with a common ODS stationary phase.