| An amperometric immunoassay for IAA in tomato embryos was developed. The antibody against IAA was covalently bound to the chemically modified inner surface of a 22 {dollar}mu{dollar}l silica capillary. The competitive binding of methylated IAA and an IIA alkaline phosphatase conjugate for a limited amount of antibody was accomplished in the silica capillary in 20 min. The enzymatic product p-aminophenol, produced from p-aminophenyl phosphate, was determined by flow injection analysis with amperometric detection. The detection limit is 3 pg/{dollar}mu{dollar}l. The average concentration of IAA in mature embryos measured by this method is {dollar}0.37pm 0.02 mu{dollar}g/g. Although isotope dilution GC-SIM-MS can achieve the same detection limit, the sample analysis is not feasible in such a complicated matrix and further purification and separation are required.; Dendrimers are macromolecules with well-defined three dimensional structures. The properties and features of dendrimers are determined by the initiator core, interior layers and terminal groups. The highly branched interior layer is composed of repeating building blocks with special functionality. The functions of the dendrimer can be carefully designed and amplified by selecting building blocks and terminal groups according to the research need. They can be made with multiple functionalities which may offer specific selectivity through well controlled synthesis and modification process. Dendrimers, regarded as covalently-fixed micelles, may offer an attractive alternative in electrokinetic chromatography (EKC).; Starburst dendrimers, polyamidoamine (PAMAM) with terminal carboxylate groups, have been used as a pseudo-stationary phase in EKC for separating selected aromatic amino acids phenylalanine (PA), phenylglycine (PG), homophenylalanine (HPA) and tyrosine (TYR), and the catecholamines DOPA and methyl-DOPA at different pHs. A significant difference in analyte selectivity was observed between dendrimers of different generations and at different pHs. At pH 7.0, the utility of the dendrimers for separating these analytes was limited by relatively low selectivity and baseline noise. Good separation and selectivity were obtained with low generation dendrimers (G0.5 and G1.5) at low pH. Strong association of the solute with dendrimers was observed for high generations (G2.5, G3.5 and G5.5). |
