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Critical evaluation of buffering solutions for pKa determination by capillary electrophoresis.

Electrophoresis (2008-06-12)
Elisabet Fuguet, Mario Reta, Carme Gibert, Martí Rosés, Elisabeth Bosch, Clara Ràfols
ABSTRACT

The performance of the most common and also some other less common CE buffers has been tested for the pKa determination of several types of compounds (pyridine, amines, and phenols). The selected buffers cover a pH ranging from 3.7 to 11.8. Whereas some buffers, like acetic acid/acetate, BisTrisH+/BisTris, TrisH+/Tris, CHES/CHES-, and CAPS/CAPS- can be used with all type of analytes, others like ammonium/ammonia, butylammonium/butylammonia, ethylammonium/ethylammonia, diethylammonium/diethylammonia, and hydrogenphosphate/phosphate are not recommended because they interact with a wide range of compounds. The rest of the tested buffers (dihydrogenphosphate/hydrogenphosphate, MES/MES-, HEPES/HEPES-, and boric acid/borate) can show specific interactions depending on the nature of the analytes, and their use in some applications should be restricted.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
MES hydrate, ≥99.5% (titration)
Sigma-Aldrich
MES, low moisture content, ≥99% (titration)
Sigma-Aldrich
MES hydrate, BioPerformance Certified, suitable for cell culture, ≥99.5%
Sigma-Aldrich
MES hydrate, ≥99.5% (titration), pH 2.5-4.0 (0.5 M in H2O), BioXtra
Sigma-Aldrich
MES sodium salt, ≥99% (titration)
Sigma-Aldrich
MES sodium salt, BioReagent, ≥99% (titration), crystalline
Sigma-Aldrich
MES solution, BioUltra, for molecular biology, 0.5 M in H2O
Sigma-Aldrich
MES sodium salt, BioPerformance Certified, suitable for cell culture
SAFC
MES sodium salt
Sigma-Aldrich
MES hydrate, BioUltra, ≥99.5% (T)