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 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.
Ando
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Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, MI 48105, USA. andoh@aa.wl.com
Heimbach
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D000631:Aminopyridines / Q000032:analysis; D001565:Benzoates / Q000032:analysis; D019817:Benzoic Acid; D002021:Buffers; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation; D004563:Electrochemistry; D017022:Flow Injection Analysis / Q000295:instrumentation; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D015203:Reproducibility of Results; D012997:Solvents
D000631:Aminopyridines; D001565:Benzoates; D002021:Buffers; D012997:Solvents; D019817:Benzoic Acid; C032439:alpha-aminopyridine