Capillary temperature optimizing resolution

Many factors can affect the separation performance of a capillary electrophoresis (CE) electrolyte, such as the buffer, surfactant and organic modiher concentrations, pH, capillary temperature, and applied voltage (1). The efficient manipulation of these factors is critical to optimize the resolution of a given analysis in the shortest time frame. 

At first the chromatographic conditions of the chiral main column must be optimized carefully. Capillary columns coated with chiral stationary phases of suitable enantio-selectivities are used as main columns. Chiral resolutions are commonly achieved isothermally or by low temperature programming rates, starting at least 20°C below precolumn temperature. Precolumns are chosen with respect to (i) the versatility of application, to (ii) the direct injection of high sample volumes and (iii) with respect to the requisite time of analysis. 

Capillary electrophoresis (CE) is an emerging analytical technique for determination of catechins. The majority of CE studies involve the analysis of catechins in tea infusion, extracts as well as supplements. The three variants of CE suitable for the analysis of catechins include capillary zone electrophoresis (CZE), micellar electro-kinetic chromatography (MEKC), and microemulsion electrokinetic chromatography (MEEKC) with UV detection. In general, the resolution of MEKC was found to be superior to CZE for separation of catechins. MEEKC is a relatively new technique, and the few reports available suggest that it offers a performance similar to MEKC. CE conditions are often quite complex, and many factors, such as buffer composition, pH, presence of surfactants, and column temperature, can all affect the quality of separation and should be optimized individually. On the other hand, CE offers several advantages over HPLC. The short analysis time (<20 minutes), low running costs, and reduced use of solvents make it an attractive alternative for routine analysis of catechins. 

When selecting the desired temperature of the capillary, consideration should be given to reproducibility of sample injection and migration times, optimization of resolution, the possibility of sample decomposition, and the minimization of analysis times [3]. 

Grob, K. Tschuor, R. Optimal carrier gas velocities at high temperatures in capillary GC. J. High Resolut. Chromatogr. 

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