Determination Of Amino Acids In Flower Of Lonicera Japonica Thunb. And Powdered Milk By Microwave Derivatization Capillary Electrophroesis

Amino acids are the builders of proteins and peptides, such as hormones,metabolic regulators, enzymes, neurotransmitter and growth factor. They play an vitalrole in organism. And now amino acids have many important applications in actuallife, such as feed additives, health products, cosmetics, medicine. So, a simple andsensitive method is necessary for the determination of amino acids.Derivatization reaction of amino acids commonly was carried out in heated waterbath. However, derivatization time was long. Compared with conventional heatedwater bath derivatization time, microwave derivatization time was relatively shorter.The derivatization efficiency had no significant difference between the microwaveand heated water bath derivatization. The capillary electrophoresis (CE) has manyadvantages, such as rapidity, small amount of sample and reagent, operation inaquecous solution and automation.The free amino acids was determined by capillary electrophroesis, and the mainexperimental factors were optimized. The free amino acids were extracted byultrasonic extraction using0.005mol/L hydrochloric acid solution as extractionsolvent. The obtained amino acids were derived by microwave derivatization with2,4-Dinitrofluorobenzene（DNFB）and determined by capillary electrophoresis(CE).When DNFB was used as a derivatization reagent, derivatization reaction wascompleted by microwave-assisted derivatization at150W for30s. So derivatizationtime was shorten. When the amino acid concentration was in the range of0.50-50.00 μg/mL, a good linear relationship exists between peak area and concentration ofamino acids, and the correlation coefficients were above0.999. The buffer consistedof40mmol/L borate solution, and pH value was9.5. The separation efficiency of CEwas high and amino acids were separated from each other within20min. The freeamino acids were determined by this method and the results were satisfactory. Therecoveries of amino acids were64.21-118.45%.The amino acids in powdered milk were determined by micellar electrokineticchromatography, and the optimizated factors were choosen. The proteins in powderedmilk could be completely hydrolyzed under130℃for15min. Compared withtraditional heated hydrolysis, there was no significant difference in derivatizationefficiency when the method was applied. Amino acids were derived with4-chloro-3,5-dinitrobenzotrifluoride (CNBF) in borate buffer (pH9.0) at240Wmicrowave irradiation power for90s. The buffer contained25mmol/L borate,50mmol/L SDS,20mmol/L1-Butyl-3-methylimidazolium tetrafluoroborate([BMIM]BF4) and7.5%(v/v) isopropanol and pH value was9.5.18amino acidswere separated and determined by micellar electrokinetic chromatography. Thelinearity correlation coefficients for these amino acids were greater than0.999in theconcentration range of1.00to80.00μg/mL. The limits of detection for the aminoacids were0.22-0.53μg/mL. The present method was applied for the determination ofamino acids in powdered milk and recoveries were61.56-108.84%.