Microwave-assisted Synthesis Of PAMAM Dendrimer Modified Open-tubular Capillary For Electrochromatography

Capillary electrochromatography(CEC)has rapidly gained interest among researchers in many different fields during recent years.It combines the high efficiency of capillary electrophoresis(CE)and the high selectivity of liquid chromatography(LC).Dendrimers are synthetic,highly branched,nearly spherical and symmetrical macromolecules with well-defined sizes and compositions.They have received a great deal of attention because of the numerous terminal functional groups.The introduction of PAMAM can improve the separation efficiency.The application of microwave dielectric heating to chemical systems is observed with a number of unique advantages compared to conventional heating including non-contact heating,rapid heating and reduced processing costs and time.In this paper,we used microwave-assisted synthesis as the synthesis psocess of the PAMAM modified capillary.The capillary used is of 751am(O.D.). After Silanization by 3-aminopropyltriethoxysilane(APTES),3G PAMAM was grown from the amino groups by repetition of two steps under microwave irradiation:(1)Michael addition of methyl acrylate(MA)to amino groups on the surface and(2)amidation of the resulting terminal ester groups with ethylenediamine(EDA).With the same conditions 1G PAMAM was introduced to quartz plate in order to simulate the capillary.The plate was characterized with SEM.PAMAM modified capillary was characterized with FITC marked fluorescence.The results indicated that PAMAM was successfully bonded to the inner wall of capillary.The obtained capillaries were characterized in EOF measurement and the separation of alanine and proline.The results showed that the modified capillary had good efficiency,reproducibility and stability.Under pH 8.0 phosphate buffer,15kV applied voltage,25℃,alanine and proline were separated well.5,10,15,20-4-carboxyphenyl porphyrin was introduced to the amino group of 3G PAMAM modified capillary.The separation of para aminobenzoic acid and para-hydroxybenzoic acid was investigated.The mixture was separated under pH 7.5 phosphate buffer,15kV applied voltage,25℃.