Capillary electrophoresis conditions optimization

Samskog, J., Wetterhall, M., Jacobsson, S., and Markides, K. (2000). Optimization of capillary-electrophoresis conditions for coupling to a mass-spectrometer via a sheathless interface. ]. Mass Spectrom. 35, 919—924. 

Analytical methods are ripe for attack using Al methods. Capillary electrophoresis is a routine separation technique, but like other separation techniques, its effectiveness is correlated strongly with experimental conditions. Hence it is important to optimize experimental conditions to achieve the maximum degree of separation. Zhang and co-workers41 studied the separation of mixtures in reserpine tablets, in which vitamin B1 and dibazolum may be incompletely separated, as may promethazine hydrochloride and chloroquine... 

A very interesting task would be automatic measurement of the product and the calculation of production rates. This would allow automatic optimization of the process by a computer program that varies all relevant parameters, probably by multiparameter analysis, to find the best production conditions. As long as there are no product sensors available, the main problem may be the time necessary for the measurement of an automatically taken sample. However, the use of HPLC methods can give accurate results within 20 min, and high-performance capillary electrophoresis (HPCE), with an analysis time of 5 min, could be introduced (Beckman PIACE 2(X)0, E. Wasserbauer, personal communication and James et al, 1994). Nonetheless, further development is necessary before these methods can be used routinely for automatic fermentation 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. 

Park, Y. N., Zhang, X., Rubakhin, S. S., and Sweedler, J. V., Independent optimization of capillary electrophoresis separation and native fluorescence detection conditions for indolamine and catecholamine measurements. Ana/. Chem., 71,4997,1999. 

Micellar electrokinetic chromatography uses ionic surfactants at a concentration above the critical micelle concentration (CMC) as a component of the run buffer chosen to separate compounds. This generates a pseudo-stationary phase that performs the separation. This technique is therefore optimal for separating neutral and charged compounds from each other. In addition compounds that are very hydrophobic, and those typically insoluble in traditional capillary electrophoresis run separate buffers under these conditions. Neutral compounds elute in the order of their hydrophobicity. 

Ren et al. [109] established a method for the simultaneous determination of anisodamine, scopolamine, atropine, and anisodine by capillary electrophoresis with electrochemiluminescence detection (CE-ECL). The concentration and pH of the running buffer as well as the methanol content additive were investigated for the improvement of selectivity and sensitivity. These four alkaloids were separated within 6 min under optimal conditions in a buffer containing 20 mmol L phosphate and 7 % methanol at pH 8.0. The method, showing RSD of the migration time less than 1.1 % and recoveries between 97.8 % and 102 %, was applied for the determination of anisodamine and scopolamine in an extract of Przewalskia tangutica. 

Assisted Approach of the Global Optimization for the Experimental Conditions in Capillary Electrophoresis. 

Capillary electrophoresis (CE) has been demonstrated for determination of LAS in wastewater and sludge. Conditions can be optimized to give either a single peak for total LAS or a series of peaks representing the alkyl chain length distribution (67). It is too early to predict whether CE will become more useful than the established methods for environmental analysis. 

FIGURE 3.3 Screening and optimization scheme developed in Perrin et al. [28]. Other conditions Injection 0.5 psi, 3.5 s Fnsed-sihca capillary or polyacrylamide-coated capillary of 30 cm X 50 xm. (Reprinted from Perrin et al. Electrophoresis 2001, 22, 3203-3215. With permission from Wiley VCH.)... 

A determination of PQQ by capillary zone electrophoresis was also developed <2000JCH(739)101>. The optimal separation conditions were a 50mM /3-alanine HCl pH 3.0 buffer, an applied voltage of 25 kV (negative polarity), and a temperature of 25 °C. The linear detection range for concentration versus peak area is that this assay is from 5 to 500 mM with a detection limit of 0.1-0.2 mM. 

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