Binding equilibrium of nine kinds of phenylalkylamines (PAA) as non-charged species to nonionic Brij 58 micelle has been investigated through the measurements of the electrophoretic mobility by capillary zone electrophoresis. Analysis of the binding equilibrium involves: (1) acid dissociation constant of PAA in an aqueous solution, Ka, (2) conditional acid dissociation constant of PAA in Brij 58 micelle solution, Ka', and (3) binding constant of PAA + as protonated species of PAA to the micelle, KB,HB. Binding constant of non-charged species of PAA to the micelle, KB,B, was then determined through the three equilibrium constants. Both binding constants of KB,HB and KB,B increased with increasing molecular volume of PAA, and linear free energy relationship was verified between the molecular volume and logarithmic value of the binding constants. Binding constants of KB,B are larger than KB,HB for every PAA. This result also suggests the hydrophobic binding that less charged species are more strongly bound to the hydrophobic surfactant micelle.

-2 -Herein, we report a novel method for the determination of polyamines in a sample extracted from Arabidopsis thaliana by capillary electrophoresis (CE) using salicylaldehyde-5-sulfonate (SAS) as a derivatizing reagent. An aldehyde group of SAS forms a Schiff base with amino groups of aliphatic polyamines, resulting in an anionic species with an absorption band in the ultraviolet region. The derivatization method was straightforward since the derivatives were formed by mixing a sample with the derivatizing reagent under a neutral pH. In addition, the negative charges induced by SAS led to a high resolution with a short analysis time. This method permitted the separation of five polyamines, which play important roles in plants. However, further improvement in sensitivity was needed for the determination of the polyamines in plant samples. Therefore, the CE method was coupled with solid-phase extraction (SPE) using an ion-pairing formation with sodium dodecyl benzene sulfonate. The SPE method improved the concentration limits of detection to sub-µM levels, which corresponded with a 10-fold enhancement. The calibration curves for cadaverine, putrescine, and spermidine were linear with concentrations that ranged from 1 to 20 µM and correlation coefficients (R 2 ) were greater than 0.998. The proposed method was applied to the determination of spermidine in a plant sample, Arabidopsis thaliana.

No abstract