500 ms lc hexapole ion trap mass spectrometer

Mass spectrometric data were obtained by means of a Varian 500-MS LC hexapole ion-trap mass spectrometer (Palo Alto, CA, USA). The experiments were performed in positive and negative ion-mode for AlaSal as well as the Co(II)–AlaSal system in 50/50% (v/v) methanol/water mixture, providing a more stable spray than water alone [65 (link)]. A background electrolyte was not added. The concentration of the ligand alone in the solution was 10⁻² M, while the AlaSal concentration in the Co(II)–ligand system was 2 × 10⁻² M at the molar ligand–metal ratio equal to 2:1. The samples were brought to various pH values known to achieve maximum concentrations of particular complexes and ionic forms of the ligand; these values were based on potentiometric species distribution graphs. All samples were introduced into the ESI-MS source by continuous infusion using an instrument syringe pump at a rate of 10 μL min⁻¹. The ESI-source was operated at 5.00 kV and the capillary heater was set to 350 °C. The cone voltage was within the range 40–120 V.

The ESI–MS and MS/MS spectra were recorded using a Varian 500-MS LC hexapole ion-trap mass spectrometer (Palo Alto, CA, USA) with an accuracy of 0.1 for m/z values. The measurements were performed for the ligand and its system with cobalt(II) in positive and negative ion modes. The test medium was a 50/50% (v/v) methanol/water mixture, providing a more stable spray and producing smaller initial droplets than water alone or a high water content solvent [43] (link). No background electrolyte was added.
The concentration of PhAlaSal was 5 × 10⁻³ M in both the ligand-only and the Co(II)–ligand samples. For the complex system, the ligand-metal molar ratio was equal to 2:1. All samples were adjusted to various pH values to maximize the formation of individual complexes and ionic forms of the ligand based on potentiometric data. The samples were introduced into the ESI–MS source by continuous infusion using an instrument syringe pump at a rate of 10 μL·min⁻¹. The ESI-source was operated at 5.00 kV and the capillary heater was set to 350 °C. The cone voltage was within the range 40–120 V.