A new derivatization approach for the rapid and sensitive analysis of brassinosteroids by using ultra high performance liquid chromatography-electrospray ionization triple quadrupole mass spectrometry.

In this work, a new labeling reagent, 2-bromopyridine-5-boronic acid (BPBA), was introduced to derivatize brassinosteroids (BRs). The BPBA not only provided a very simple and rapid labeling procedure, but also remarkably increased the detection sensitivity of BRs. Based on this new labeling reaction, a rapid and sensitive method for BRs' analysis in Arabidopsis thaliana was established by using the ultra high performance liquid chromatography-electrospray ionization triple quadrupole mass spectrometry (UHPLC-ESI-QqQ-MS). The extraction and purification procedure of the plant sample was also simplified and improved in this work. Good linearities were obtained for three BRs with the determination coefficients (R(2)) about 0.9999. The limits of detection (S/N=3) for three BRs were found to be 2.00-8.00 ng/L while the limits of quantification (S/N=10) were 6.00-23.0 ng/L. The RSD % for all three samples are lower than 8.67% (n=5). The recoveries of three BRs spiked in A. thaliana samples were from 76.9% to 86.1%. Using this method, the endogenous 0.055 ng/g fresh weight (FW) 24-epiBR and 0.070 ng/g (FW) 28-epihomoBR were successfully detected from only 2g A. thaliana plants.