pKa determinations by using a HPLC equipped with DAD as a flow injection apparatus

A semi-automated method to determine pKa values spectrophotometrically is described. The method uses the capabilities of a HPLC equipped with a diode array detector (DAD) as a flow injection apparatus. The advantages are low sample consumption, rapid sample throughput, high sensitivity, and precisio...

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Bibliographic Details
Published in:Journal of pharmaceutical and biomedical analysis 1997-09, Vol.16 (1), p.31-37
Main Authors: ANDO, H. Y, HEIMBACH, T
Format: Article
Language:English
Subjects:
Aminopyridines - analysis
Analysis
Benzoates - analysis
Benzoic Acid
Biological and medical sciences
Buffers
Chromatography, High Pressure Liquid - instrumentation
Electrochemistry
Flow Injection Analysis - instrumentation
General pharmacology
Hydrogen-Ion Concentration
Medical sciences
Osmolar Concentration
Pharmacology. Drug treatments
Reproducibility of Results
Solvents
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Summary:A semi-automated method to determine pKa values spectrophotometrically is described. The method uses the capabilities of a HPLC equipped with a diode array detector (DAD) as a flow injection apparatus. The advantages are low sample consumption, rapid sample throughput, high sensitivity, and precision. Experimental pKa values obtained for two model compounds, benzoic acid (approximately 4.0) and 2-aminopyridine (approximately 6.8), are consistent with literature values. Constant ionic strength was maintained for a wide pH range. Solubilized samples in non-aqueous solvents were also investigated. The weakening in pKa values, often seen when using non-aqueous solvents, was small (0.04-0.40 pH units) compared to conventional methods.
ISSN:0731-7085
1873-264X
DOI:10.1016/S0731-7085(97)00084-8