Ltq velos ms system

The HPLC–MS system comprised an Accela 1250 UHPLC system (Thermo Fisher) coupled to an LTQ Velos MS system (Thermo Fisher) with an APCI ion source operating in positive ion mode. The HPLC system consisted of a thermostated Accela autosampler with a 25-μL loop, a quaternary high-pressure Accela pump, and a diode array Accela PDA detector. Xcalibur software (Version 2.1.) was used for evaluation of chromatograms. All HPLC conditions were the same as stated above for HPLC–PDA analysis, only solvent B was replaced with water. APCI ion source conditions were as follows: Transfer capillary temperature 275 °C, vaporizer temperature 300 °C, spray voltage 5 kV, discharge current 3 μA, sheath gas flow rate 35 a.u., and auxiliary gas flow rate 5 a.u. MS and MSⁿ spectra were acquired in a 200–1200 m/z range. For fragmentation of selected ions, different collision energies (30–45%) were applied.

For a direct coupling of HPTLC to an ion trap LTQ Velos MS system (Thermo Fisher, San Jose, Ca, USA), a TLC–MS interface (Camag) was used. Elution of zones of interest from the plates was performed by using methanol:dichloromethane (3:1, v/v) as an elution solvent. The flow rate was maintained at 200 μL/min and 0.2% acetic acid in methanol was added to the HPTLC effluent in a ratio of 1:40 prior to the introduction of the solution into the MS system. Atmospheric pressure chemical ionization (APCI) in positive ion mode was used. Ion source parameters were set as: Transfer capillary and vaporizer temperature 300 °C, sheath gas flow rate 30 a.u. (arbitrary units), auxiliary gas 10 a.u., spray voltage 3 kV, and discharge current 3 μA. MSⁿ experiments were carried out by fragmentation of target precursor ions (isolation width 2 amu) using different collision energies (30–45%). MS and MSⁿ spectra were acquired in the 200–1500 m/z range. The MS background was subtracted by sampling the HPTLC plate between tracks at the same R_F value as the measured band. Acquired MS spectra were processed using Xcalibur software (Version 2.1.).