TITLE

Automated determination of the p K a values of 4-hydroxybenzoic acid in cosolvent–water mixtures and related solvent effects using a modified HPLC system

AUTHOR(S)
Miklautz, H.; Keller, D.; Holguin, F. Lopez; Woloszczak, R.
PUB. DATE
March 2006
SOURCE
Analytical & Bioanalytical Chemistry;Mar2006, Vol. 384 Issue 5, p1191
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
An automated spectrophotometric method based on an HPLC system with a diode array detector was used to determine the p K a values of compounds with low water solubility in a universal buffer containing acetonitrile as cosolvent. The column of the system was replaced with a capillary connecting the injection system and the diode array detector. Specific solvent effects were corrected for using the dielectric constants of the mixed solvent and pure water. The method was tested using 4-hydroxybenzoic acid and the results were compared with those obtained with a spectrophotometer. Linear regression lines with different slopes were obtained from spectrophotometric measurements of different cosolvent–water mixtures. These effects were shown to depend upon the polarity of the solventwater mixture, and they were explained by the solvatochromic behavior of the 4-hydroxybenzoic acid in the solvent–water mixture.
ACCESSION #
19933195

 

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