Turbomatrix 150

The volatile organic compounds (VOCs) of mutant Bacillus and Streptomyces strains were investigated using gas chromatographymass spectrometry (GC-MS) and a thermal desorber (TD). In a 500 mL Erlenmeyer flask, the bacteria were inoculated into liquid nutrient medium. With the help of a rubber cork, a tenax-coated stainless-steel column was fitted with the flask. The VOCs collected by the column were analysed using TD-GC-MS on a TurboMatrix 150 (Perkin Elmer, USA). For separation, a non-polar capillary column (30 m, 250 µm) coated with 5% phenyl methyl siloxane was utilised. The following temperature regime resulted in volatile separation: the initial oven temperature of 50°C was increased to 250°C at a rate of 10°C per min; the injection port was kept in split mode with a 1:10 split ratio; and the carrier gas was helium at a constant flow rate of 0.7 mL min -1 . The MS settings were as follows: full scan mode; scan range of 0.2 s at intervals of 0.1 s; electron impact spectra of 70 eV; and positive ion mode. By comparing the collected mass spectra to the NIST/EPA/NIH Mass Spectral Library, NIST 14, the VOC was identified. The approach described by Passari et al. [47] was used for VOC detection and analysis.

An ATD-GC-MS equipment from Perkin-Elmer (Turbomatrix 150 and Clarus 500-560) was used . Between 10 to 15 mg of materials were placed inside a thermo desorption glass tube (Supelco 29538). Thermo-desorption (TD) was performed by heating the tube at 180°C during 5 min in the ATD and inlet and outlet splits were set so that a dilution factor of 330 was obtained.
Gas chromatography (GC) separation was performed with a 15 meters 5ms column (S2B-5MS Supelco) at 100°C and 10 psi, with helium as carrier gas. The mass spectrometer detector was used at the end of the column. The ion source temperature was set to 200 °C. Mass spectra were obtained by electronic ionization at 70 eV from 35 to 200 m/z. The amount of thymol was deduced from the calibration with known thymol concentrations in methanol performed in the same conditions. Duplicates were performed from two different impregnation runs.