Kinetex f5 lc column

Liquid chromatography–electrospray ionisation mass spectrometry (LC-ESI-MS) was used to analyse the molecular weights of the peak fractions of EEAS. These were separated using a Kinetex F5 LC column (150 × 4.6 mm; 5 µm) (Phenomenex, UK) with UV detection at 220–256 nm on a Spectra System LC (Thermo Separation Products) as previously reported [30 (link)].

An LTQ XL Linear Ion Trap coupled with Surveyor MS Pump Plus (Thermo Scientific, Waltham, MS, USA) was used with sheath and auxiliary gas flow at 40 and 10 arbitrary units, respectively, capillary temperature 275 °C, isolation width 1.0, with source voltage at 3.5 kV (negative ionization) and 5 kV (positive ionization). Separations were achieved using a Kinetex F5 LC column (2.6 μm, 150 × 2.1 mm, Phenomenex) and mobile phases (A) water and (B) 95% CH₃CN, both containing 2 mM formic acid and 3.6 mM ammonium formate. The gradient (0.2 mL min⁻¹) was A 75–30% over 6 min, 30–75% A over 3 min, and held at 75% A for 2 min, with 20 μL full-loop injections.
Oxidized standards (10 μg mL⁻¹) of MC-LR (9), [ADMAdda⁵]MC-LR (3) and [DMAdda⁵]MC-LR (1) were scanned in negative ionization mode. A list of target molecular ions was generated based on full-scan mass spectra. MS/MS spectra (negative ionization) were obtained using 20% CE for m/z 207 (MMPB), m/z 193 (2R-methyl-3S-hydroxy-4-phenylbutanoic acid (MHPB)) and m/z 291 (2-methyl-3-oxo-4R-methyl-5S-acetyloxy-6-phenylhexanoic acid (MOMAPH)). MS/MS/MS spectra were obtained for additional characterization of m/z 291 (MOMAPH) using 35% CE of the dominant product ion in the MS/MS spectrum (m/z 231). Positive ionization was also used for MS/MS characterization of m/z 293 (MOMAPH).