New modified coated carbon fiber as solid phase for microextraction and in-situ derivatization of phytohormones in real samples.

Phytohormones play a vital role in plant growth and metabolic processes1. As a minor component of the metabolome, phytohormones are of particular significance due to their role in the regulation of germination, growth, reproduction, and the protective responses of plants against stress. In fact, they control the balanced response of plants to adverse environmental conditions or biological threats. Thus, the simultaneous quantitative profiling of different classes of phytohormones provides a useful basis for defining additive, synergistic or antagonistic hormonal activities in biofertilizers or natural compounds. Phytohormones are typically present at trace levels in biological matrices, and the coexistence of a wide variety of interferents make their analysis rather challenging2. In this work, an integrated sample pre-treatment and derivatization method based on a new coated carbon fiber microextraction that allows a rapid extraction, separation, and highly sensitive phytohormone detection has been realized and characterized. Carbon fibers, chosen as substrate for their excellent high thermal and chemical stabilities, high porosity, and low cost, were chemically modified to obtain new surface characteristics in terms of polarity and adsorbing capacities. Three phytohormones (jasmonic acid, indole-3-acetic acid and abscisic acid) were simultaneously extracted, in-situ derivatized with N,O-bis(trimethylsilyl)trifluroacetamide and directly subjected to analysis by gas chromatography‒mass spectrometry. The developed method allowed in few step and short time low detection limits (0.62 – 3.72 ng mL‒1), good linearity (in the range 3.0 – 5000 ng mL‒1) and recoveries (81.6 to 105.8%). Furthermore, enrichment response factors (calculated as the ratio of peak areas obtained by SPME thermal desorption and direct injection) up to 3200, high derivatization rates (≥ 90%) and good reproducibility (RSD ≤ 20% at 50 ng mL-1) were obtained. The developed method was applied for the evaluation of phytohormone concentration in blended tomato samples.