Determination of acid dissociation constants of triazole fungicides bypressure assisted capillary electrophoresis
Abstract
tPressure assisted capillary electrophoresis was applied to determination of acid dissociation constants(pKa) of six widely used triazole fungicides (cyproconazole, epoxiconazole, flusilazole, tebuconazole, pen-conazole and propiconazole) in aqueous medium. The pKavalues were determined from the dependenceof effective electrophoretic mobility of the triazole fungicides on p[H+] of the background electrolyte(BGE) using non-linear regression analysis.
The p[H+] was used instead of pH to reflect the increasedionic strength of the strongly acidic BGEs (pH < 1.75) as compared to the BGEs at pH equal to or greaterthan 1.75. Prior to the pKacalculation, the measured effective electrophoretic mobilities were correctedto the reference temperature (25°C) and constant ionic strength (25 mM).
The regression function wasmodified to allow the determination of pKain the BGEs of varying ionic strength. The electrophoreticmeasurements showed that the above triazole fungicides are very weak bases - their pKavalues werefound to be in the range 1.05-1.97 and were in a good agreement with the values calculated by SPARConline pKacalculator.