Solarix xr 9.4t

HPLC–MS was carried out using an Agilent 1200 HPLC fitted with an Atlantis^® T3 column (Waters, cortecs 2.7 µm, 3 × 150 mm); the column temperature was maintained at 25 °C. The HPLC was coupled to an electrospray FT-ICR mass spectrometer (Bruker solariX XR 9.4T). The mobile phase was composed of water (A) and acetonitrile (B) both with 0.1% (v/v) formic acid, and the following gradient was used: 5% B increasing linearly to 95% over 22 min and held for 2 min. B was then returned to 5% over 0.33 min and held for 5.33 min to allow column equilibration. The flow rate was 300 µL/min and the injection volume was 5 µL.

Mass spectrometry images were obtained as recently described (76 (link)) using an FT-ICR mass spectrometer (SolariX XR 9.4T, Bruker Daltonics, Bremen, Germany) mass calibrated from 200 m/z to 2,300 m/z to reach a mass accuracy of 0.5 ppm. A region of interest from agar microbial colonies was directly collected from the petri dish and transferred onto an indium tin oxide (ITO) glass slide (Bruker, Bremen, Germany) previously covered with double-sided conductive carbon tape. The samples were dried under vacuum and covered with an α-cyano-4-hydroxycinnamic acid matrix solution at 5 mg/mL (70:30 acetonitrile:water [vol/vol]). In total, 60 layers of α-cyano-4-hydroxycinnamic acid matrix were sprayed using a SunCollect instrument (SunChrom, Friedrichsdorf, Germany). FlexImaging 5.0 (Bruker Daltonics, Bremen, Germany) software was used for MALDI-FT-ICR MS imaging acquisition, with a pixel step size for the surface raster set to 100 μm.

The high-resolution mass spectrometry analysis was performed using a SolarixXR 9.4 T (Bruker, Germany), equipped with an electrospray ionization (ESI, Bruker) source, set in negative ionization mode. The instrument was externally calibrated with Tuning Mix from Agilent. Samples were infused directly into the ESI source. The parameters were optimized to obtain a stable ion current with a minima ion injecting time into the mass analyser. The infusion flow rate was 2.0 µL min⁻¹, the drying gas temperature was 200 °C, and the drying and nebulizing gas flow rate were 4.0 L min⁻¹ and 1 bar, respectively. The ESI capillary voltage was 3.9 kV. Three hundred scans were accumulated for each spectrum. Methanol was injected prior to the injection of each sample, and acquisition was performed to evaluate the potential presence of residual pollutants. The acquisition size was set to 8 M, resulting in a mass resolving power of up to (6.6 ± 1.6) × 10⁵ for the full mass range.