In current study, we developed a highly sensitive method for the quantitative profiling of acidic phytohormones. Tandem solid-phase extraction (SPE) and liquid-liquid extraction (LLE) was employed to efficiently purify acidic phytohormones, which were further derived by 3-bromoactonyltrimethylammonium bromide (BTA) to increase the ionization efficiency in electrospray ionization-mass spectrometry detection. Additionally, fifteen BTA-derived acidic phytohormones, including ten gibberellins (GAs), were well separated with a salt gradient on poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) monolithic column. By employing online trapping system, the signal intensities of the analytes were significantly improved. The limits of detection (LODs, Signal/Noise=3) of targeted phytohormones ranged from 1.05 to 122.4 pg/mL, which allowed the highly sensitive determination of low abundant acidic phytohormones with tiny amount plant sample. Good reproducibility was obtained by evaluating the intra- and inter-day precisions with relative standard deviations (RSDs) less than 10.9 and 11.9%, respectively. Recoveries of the target analytes from spiked rice leave samples ranged from 88.3 to 104.3%. By employing the method developed here, we were able to simultaneously determine 11 endogenous acidic phytohormones from only 5mg of rice leave sample, which dramatically decreased the required sample amount (three orders of magnitude lower) for the profiling of low abundant acidic phytohormones compared to previous reports. Taken together, the method provided a good solution for the highly sensitive and quantitative profiling of endogenous acidic phytohormones.
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