Analysis procedure of strigol

Before analyzing strigol levels of plant samples, the standard sample of strigol purchased from OLChemim Ltd. (Olomouc, Czech Republic) was used to optimize parameters to obtain maximal signal intensities of strigol in HPLC-ESI-MSn. The optimum procedure was as follows: The elution gradient of HPLC was performed with 95% A (0.1% formic acid in water) and 5% B (methanol) at constant flow rate of 0.15 mL/min for 1 min; A decreased to 60% and B increased to 40% in 9 min; then A decreased to 0 and B increased to 100% at 20 min, which should hold on for 5 min; after that, A and B reached the original percent in 1 min and held on for 5 min. Then, a LCQ DECA XP MAX ion trap mass spectrometer system (Thermo-Finnigan) coupled with an ESI source was used with the following parameters: positive ionization mode, Capillary temperature 300 °C, sheath gas: nitrogen, 30abi units, Aux gas: nitrogen, 5abi units (ca. 3.33 L/min), Capillary voltage + 4.0 kV, Tube Lens Offset 30 V, Multiple RF Amplifier 400Vp-p, Multiple 1 Offset − 6.80 V, Multiple 2 Offset − 9.50 V, Inter-multiple Lens Voltage − 16.00 V, Entrance Lens -50 V, Trap DC Offset Voltage -10 V, Capillary temperature 280 °C, Collision energy 35 eV.