GC-MS Analysis of Root Metabolites

GC-MS analyses were performed using Agilent 5975C mass selective detector coupled to a 7890A gas chromatograph (Agilent Technologies, Santa Clara, CA, United States) with 7693 autosampler and a DB-5MS DG capillary column (30 m plus 10 m Duraguard^®) with a diameter of 0.25 mm, film thickness of 0.25 μm (Agilent J &W, Santa Clara, CA, United States) as described by Mamer et al. (2013) (link). The GC-MS was run in electron ionization mode (70 eV) and Selected Ion Monitoring (SIM) mode. Data acquisition was done in Scan and SIM modes using MassHunter (Agilent) software. The spectra obtained were compared against the NIST (National Institute of Standards) database. The root samples had large amounts of malic and citric acids, and were diluted 1:40 before being run again in Scan mode. While root exudates did not require dilution. Data were represented as normalized area which is the area of peak divided by amount of sample in mg (roots) or μL (root exudates).