Measurement of Dissociation Constants (pKa Values) of Organic Compounds by Multiplexed Capillary Electrophoresis Using Aqueous and Cosolvent Buffers**Advanced Analytical Technologies, Inc. (Formerly CombiSep), 2711 South Loop Drive, Suite 4200, Ames, IA 50010.

2008 ◽  
Vol 97 (7) ◽  
pp. 2581-2606 ◽  
Author(s):  
Marina Shalaeva ◽  
Jeremy Kenseth ◽  
Franco Lombardo ◽  
Andrea Bastin
Keyword(s):  
Capillary Electrophoresis ◽  
Organic Compounds ◽  
Dissociation Constants ◽  
Pka Values ◽  
Multiplexed Capillary Electrophoresis

Evaluation of the Potential of a Charge-Injection Device for DNA Sequencing by Multiplexed Capillary Electrophoresis

1995 ◽  
Vol 49 (6) ◽  
pp. 825-833 ◽  
Author(s):  
Qingbo Li ◽  
Edward S. Yeung
Keyword(s):  
Capillary Electrophoresis ◽  
Dna Sequencing ◽  
Fluorescence Detection ◽  
Charge Injection ◽  
Laser Induced Fluorescence ◽  
Array Detector ◽  
Injection Device ◽  
Laser Induced Fluorescence Detection ◽  
Array Detectors ◽  
Multiplexed Capillary Electrophoresis

Despite the rapid growth in the use of imaging detectors in spectroscopy, the charge-injection device (CID) has unique features that have not been fully exploited. The advantages of the CID as a two-dimensional array detector for laser-induced fluorescence detection in highly multiplexed capillary electrophoresis are evaluated. In such a system, the CID maintains both high sensitivity and high sampling rate, which are usually difficult to achieve simultaneously with other array detectors. Applying the electronic windowing function significantly improves the scan rate and greatly reduces the volume of data generated. With 1-s exposure time and 488-nm excitation, the detection limit of the system is 10−12 M fluorescein with the device cryogenically cooled and 10−11 M fluorescein at ambient temperature. The low dark current of the CID imager allows operation at room temperature without significantly affecting sensitivity when combined with moderate laser powers. We demonstrate that the CID is well suited for high-speed, high-throughput DNA sequencing based on multiplexed capillary electrophoresis with on-column laser-induced fluorescence detection.

Determination of dissociation constants of p-hydroxybenzophenone in aqueous organic mixtures – Solvent effects

2008 ◽  
Vol 86 (5) ◽  
pp. 462-469 ◽  
Author(s):  
M I Sancho ◽  
A H Jubert ◽  
S E Blanco ◽  
F H Ferretti ◽  
E A Castro
Keyword(s):  
Solvent Effects ◽  
Dissociation Constants ◽  
Reaction Medium ◽  
Reversed Phase ◽  
Glass Electrode ◽  
Molecular Structures ◽  
Acid Dissociation ◽  
Acidity Constant ◽  
Pka Values ◽  
Solvent Water

The apparent acidity constant of p-hydroxybenzophenone, which is a practically insoluble drug in water but of great pharmaceutical interest, was determined by reversed-phase high-performance liquid chromatography in organic solvent – water mixtures (acetonitrile–water, ethanol–water, and methanol–water), varying the reaction medium permittivity in the interval 56 to 70, at constant ionic strength (0.050) and temperature (30 °C). A combined glass electrode calibrated with aqueous standard buffers was used to obtain pH readings based on the concentration scale (swpH). The pKa values from chromatographic data were obtained using the Hardcastle–Jano equation. Moreover, excellent linear relationships between the pKa values and solvation properties of the reaction medium (relative permittivity and Acity) were used to derive acid dissociation constants in aqueous solution. It has been concluded that the pKa values extrapolated from such solvent–water mixtures are consistent with each other and with previously reported measurements. In addition, the molecular structures of all the chemical species involved in the acid–base dissociation equilibrium studied were calculated with a B3LYP/6–311++G(d,p) method that makes use of the polarizable continuum model (PCM). Taking into account the theoretical pKa values, the conclusions obtained match our experimental determinations.Key words: solvent effects, p-hydroxybenzophenone, acidity constant, solvation parameters, structure, DFT calculation.

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