Autospec ultima mass spectrometer

Coupled gas chromatography–mass spectrometry (GC‐MS) analysis was performed using a Waters Autospec Ultima mass spectrometer (+EI, 70 eV, source temperature 250 °C, m/z 40–500) coupled to an Agilent 6890 GC fitted with a DB‐1 capillary column (J & W Scientific, 50 m × 0.32 mm id × 0.52 µm film thickness) and a cool on‐column injector. The oven temperature was programmed to start at 30 °C for 5 min, then increase at 5 °C min⁻¹ until 250 °C, with a final hold of 10 min. The carrier gas was helium. Tentative identification of the EAG‐active compound for C. sordidus was confirmed by comparison of GC retention time and peak enhancement using an authentic sample of (2R,5S)‐theaspirane.11

Volatile extracts were analyzed on a GC (Agilent Technologies, 6890 N, Stockport, UK), equipped with an FID and a HP-1 capillary column (50 m × 0.32 mm i.d., 0.52 μm film thickness). The oven temperature was maintained at 30 °C for 1 min and programmed at 5 °C/min to 150 °C, where it was held for 0.1 min, then at 10 °C /min to 230 °C and held for 27 min. The carrier gas was hydrogen. One μL of sample was injected into the injection port of the equipment manually. GC-MS analysis of eluted volatiles was performed using a Waters Autospec Ultima mass spectrometer couple to an Agilent 6890 GC fitted with a HP-1 capillary column (50 m × 0.32 mm id, 0.52 μm film thickness). Ionization was by electron impact (70 eV, source temperature 220 °C). Helium was the carrier gas. The oven temperature was maintained at 30 °C for 5 min, and then programmed at 5 °C/min to 250 °C. Tentative identifications were made by comparison of mass spectra with NIST 2005 mass spectral database. Confirmation of peak identity was made by comparison of their Kováts index (KI) values and GC peak enhancement with authentic compounds. Compounds were quantified using the single point external method with an n-alkane (C₇-C₂₂) mixture. Statistical analysis of cowpea volatile data (ng/h) was done using two-sample t-test on log-transformed values (GenStat version 16).