Simultaneous separation of jasmonic acid conjugates with amino acids by MEKC

Jasmonic acid (JA) conjugates with amino acids (AAs) are a group of plant hormone in the family of jasmonates. The separation of stereoisomers of JA-AA conjugates is a very challenging work since these stereoisomers have similar chromatographic and electrophoretic behavior. Simultaneous separation of ten (+/-)-JA conjugates with five AAs including l-Tyr (tyrosine), l-leucine, l-Ile (isoleucine), l-valine, and l-phenylalanine and their stereoisomers has been achieved by MEKC with diode array detector in this work. Optimum separation of the analytes was obtained on a 61.5 cm x 75 m id capillary using a running buffer containing 80 mM SDS and 50 mM phosphates (pH 7.0) at +18 kV applied voltage and capillary temperature of 35 degrees C. Ten stereoisomers of JA conjugates with five AAs are completely separated in 13 min. The RSDs of the migration times and peak areas of the ten stereoisomers were in the range of 0.48-1.03% and 1.03-2.07%, respectively. In the tested concentration range, good linear relationships (correlation coefficients above 99%) between peak areas and concentrations of the analytes were observed. The proposed method has been successfully applied to the analysis of spiked rice floret sample and original reaction solution of (+/-)-JA-Ile conjugate and (+/-)-JA-Tyr conjugate. The recoveries ranged from 91.7 to 107.6% for the rice floret sample and 92.9 to 107.2% for the original reaction solution.