Dual-cloud point extraction and tertiary amine labeling for selective and sensitive capillary electrophoresis-electrochemiluminescent detection of auxins

The low concentrations of the auxins in samples of plant tissue necessitate the use of selective and sensitive techniques for their quantification Herein a selective and sensitive method based on dual-cloud point extraction (dCPE) and tertiary amine labeling for the quantification of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) by capillary electrophoresis-electrochemiluminescence (CE-ECL) is proposed The procedure foe dCPE included two cloud point processes with Triton X-114 as the extractant The two auxins became hydrophobic in an acidic solution and were extracted into surfactant-rich phase after the first cloud point procedure They were then back-extracted into the alkaline aqueous phase during the second cloud point step The extracted auxins were reacted with 2-(2-aminoethyl)-1-methylpytrolidine (AEMP) in acetonitrile that contained N,N'-dicyclohexylcarbodimide and 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine to produce their AEMP-derivatives The two auxin-AEMP-derivatives were subjected into CE and detected by Ru(bpy)(3)(2+)-based ECL. The preconcentration factors for IAA and IBA with dCPE were 40.5 and 43.4, respectively The on-capillary detection limits (S/N=3) were 2.5 and 2.8 nM for IAA and IBA This protocol presents a cleat advantage in that it reduces the interference from the matrixes extensively and gives a high sensitivity foe the detection of auxins The proposed method was applied successfully to the detection of the two auxins in acacia tender leaves. buds, and bean sprout (C) 2000 Elsevier B.V. All rights reserved