Lct premier xe time of flight mass spectrometer

LC-MS analyses were performed on the Acquity UPLC system with 2996 PDA detection system (194 - 600 nm) connected to LCT premier XE time-of-flight mass spectrometer (Waters, USA). Five μL of sample was loaded onto the Acquity UPLC BEH C18 LC column (50 mm × 2.1 mm I.D., particle size 1.7 μm, Waters) kept at 40°C and eluted with a two-component mobile phase, A and B, consisting of 0.1% formic acid and acetonitrile, respectively, at the flow rate of 0.4 mL min⁻¹. The analyses were performed under a linear gradient program (min/%B) 0/5; 1.5/5; 15/70; 18/99 followed by a 1.0-min column clean-up (99% B) and 1.5-min equilibration (5% B). The mass spectrometer operated in the positive “W” mode with capillary voltage set at +2,800 V, cone voltage +40 V, desolvation gas temperature, 350°C; ion source block temperature, 120°C; cone gas flow, 50 L h⁻¹; desolvation gas flow, 800 L h⁻¹; scan time of 0.15 s; inter-scan delay of 0.01 s. The mass accuracy was kept below 6 ppm using lock spray technology with leucine enkephalin as the reference compound (2 ng μL⁻¹, 5 μL min⁻¹). MS chromatograms were extracted for [M+H]⁺ ions with the tolerance window of 0.03 Da, smoothed with mean smoothing method (window size; 4 scans, number of smooths, 2). The data were processed by MassLynx V4.1 (Waters).

The samples were analyzed on an Acquity UPLC system with an LCT premier XE time-of-flight mass spectrometer (Waters, USA) using the LC Column Acquity UPLC BEH C₁₈ kept at the temperature of 30°C (50 mm × 2.1 mm I.D., particle size 1.7 μm, Waters, USA) and a two-component mobile phase at the flow rate of 0.4 ml/min. The mass spectrometer was operated in the “W” mode with the capillary voltage set at +2800 (positive ionization mode) or -2500 V (negative ionization mode), cone voltage of +40 or -40 V, desolvation gas temperature of 350°C, ion source block temperature of 120°C, cone gas flow of 50 l/h, desolvation gas flow of 800 l/h, scan time of 0.1 s, and inter-scan delay of 0.01 s. Fragmentation by collision-induced dissociation (CID) was triggered by setting the aperture 1 value at 50 V. Lincomycin quantification was performed using a standard of lincomycin A spiked into the analyte-free cultivation broth at the required concentration. The data were processed using MassLynx V4.1, and the quantification was performed using the QuanLynx application manager (Waters). Tentative identification of the structures was based on the elemental composition determined from accurate mass and isotopic patterns and, for some of the structures, on in-source CID MS fragmentation and comparison of retention times with those of available authentic standards.

LC-MS analyses were performed on the Acquity UPLC system with LCT premier XE time-of-flight mass spectrometer (Waters, USA). Five µL of sample were loaded onto the Acquity UPLC CSH C18 LC column (50 mm × 2.1 mm I.D., particle size 1.7 μm, Waters) kept at 40 °C and eluted with a two-component mobile phase, A and B, consisting of 0.1% formic acid (98–100%, Merck, Germany) and acetonitrile (LC-MS grade, Biosolve, Netherlands), respectively. The analyses were performed under a linear gradient program (min/%B) 0/5, 1.5/5, 12.5/58 followed by a 1.5-min column clean-up (100% B) and 1.5-min equilibration (5% B), at the flow rate of 0.4 mL min⁻¹. The mass spectrometer operated in the “W” mode with capillary voltage set at +/−2800 V, cone voltage +/−40 V, desolvation gas temperature, 350 °C; ion source block temperature, 120 °C; cone gas flow, 50 Lh⁻¹; desolvation gas flow, 800 Lh⁻¹; scan time of 0.15 s; inter-scan delay of 0.01 s; inter-scan delay between polarity switch, 0.1 s. The mass accuracy was kept below 5 ppm using lock spray technology with leucine enkephalin as the reference compound (2 ng μL⁻¹, 5 μL min⁻¹). Chromatograms were extracted for [M + H]⁺ or [M − H]⁻ ions with the tolerance window of 0.05 Da. The data were processed by MassLynx V4.1 (Waters).