Quattro ultima mass spectrometer

The analysis of aminoglycosides in the sewage samples was performed as in Bello^{53 (link)}, with adaptations as summarized in the following. For sample pretreatment, two 10-mL portions of each sample of sewage were weighed into separate 50-mL tubes, after which internal standards were added. To one of these portions, aminoglycosides were added at a level of 50 μg/L. Twenty mL of extraction liquid (10 mM KH₂PO₄ with 0.4 mM EDTA and 2% TCA) were added, and samples were mixed by means of a vortex and shaken head-over-head for 10 min. The extract was then brought to pH 7.6–7.9 and centrifuged (15 min, 3600 × g). The complete extract was transferred to a conditioned CBX cartridge, followed by washing with 4 mL of water and drying. The aminoglycosides were eluted with 3 mL of acetic acid (10% in MeOH). The eluate was dried at 60 °C, evaporated under N₂ and taken up in 400 μL of HFBA (0.065%). For LC-MS/MS, the following gradient was applied: 0–0.5 min, 0% B; 0.5–5 min, linear increase to 45% B; 5–8 min, linear increase to 60% B; 8–10 min, linear increase to 100% B. The injection volume was 40 μL. Detection was carried out by a Waters (Milford, MA, USA) Quattro Ultima mass spectrometer in positive ESI mode. The parameters used were: capillary voltage, 2.7 kV; desolvation temperature, 500 °C; source temperature, 120 °C; cone gas, 150 L/h; and desolvation gas 550 L/h.

For the period which ONS was being consumed, the expired air of each participant was sampled at a flow rate of 45 mL/min⁻¹, through a plastic tube inserted into the exterior opening of the nostril. A MS-Nose™ (Micromass, Manchester, UK) interface and a Quattro Ultima mass spectrometer (Waters Corporation, Milford, MA) was used to monitor the in-mouth release of four aroma molecules in real-time. The molecules were isoamyl acetate (m/z 130), isoamyl propionate (m/z 144), isoamyl isovalerate (m/z 172), ethyl butyrate (m/z 116). These flavour molecules have previously been identified as significant aroma-active contributors to the flavour of banana flavour ONS (data not yet published).

The cheese samples were analysed in full scan mode, using the MS Nose interface (Micromass, Manchester, UK) fitted to a Quattro Ultima mass spectrometer (Waters Corporation, Milford, MA) (Fernández-Vázquez et al., 2013 ). Following the method described by Gan, Soukoulis, and Fisk (2014) (link), ions of mass to charge (m/z) ratios from 40–200 were monitored. The intensity of these ions was measured at a cone voltage of 20 V, source temperature of 75 °C and dwell time of 0.5 s. All analyses were run in triplicate (Ashraf, Linforth, Bealin-Kelly, Smart, & Taylor, 2010 ).