The gas chromatography/electron impact mass spectrometry (GC/EI-MS) analysis is carried out using an Agilent 5973 Network mass selective detector connected to an Agilent 6890 gas chromatograph equipped with a capillary DB-23 column (30 m x 0.25 mm; 0.25 µm coating thickness; J&W Scientific, Agilent). Helium is used as a carrier gas at a flow rate of 1 ml/min. The temperature gradient is as follows: 150 °C for 1 min, 150 – 200 °C at 4 K/min, 200 – 250 °C at 5 K/min and 250 °C for 10 min. Electron energy of 70 eV, an ion source temperature of 230 °C, and a temperature of 260 °C for the transfer line are used.
Castor oil is used as an internal standard to determine the recovery of esterified JA, esterified oPDA and esterified dinor-oPDA. For derivatization, 1 µl of BSTFA solution is added to the sample. For quantification, the ions m/z 224 (JA), 238 (oPDA) and 210 (dinor-oPDA) are used, respectively. Calibration curves (five point measurements) for JA, oPDA and dinor-oPDA were established.
standards are available from Sigma (Germany) Larodan (Sweden), Cayman Chemical (USA), kindly provided by Mats Hamberg (Stockholm, Sweden) and Otto Miersch (Halle/Salle, Germany) or enzymatically synthesized, respectively
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