Argon ions reaction with nitrogen

The ions or cluster ions are thermalized by collisions with an inert carrier gas (usually helium), although often argon or even nitrogen is employed. Neutral reactant gas is added through a reactant gas inlet at an appropriate location downstream in the flow tube, and allowed to react with the injected ions. Rate coefficients, k, are determined by establishing pseudo-first-order reaction conditions in which the reactant ion concentration is small compared to the reactant neutral concentration. Bimolecular rate coefficients, k, are obtained from the slope of the natural logarithm of the measured signal intensity, /, of the reactant ion versus the flow rate (2b of reactant gas 45,48-50... 

For the detection, a tandem mass spectrometer Quattro Micro API ESCI (Waters Corp., Milford, MA) with a triple quadrupole was employed. The instrument was operated in electrospray in the positive ionization mode (ESI+) with the following optimized parameters capillary voltage, 0.5 kV source block temperature, 130 °C nebulization and desolvation gas (nitrogen) heated at 400 °C and delivered at 800 L/h, and as cone gas at 50 L/h collision cell pressure, 3 x 1(F6 bar (argon). Data was recorded in the multiple reaction monitoring (MRM) mode by selection of the two most intense precursor-to-product ion transitions for each analyte, except for the ISs, for which only one transition was monitored. The most intense transition for each analyte was used for quantitative purposes. Table 2 shows MRM transitions, cone voltages and collision energies used for the analysis of the antidepressants included in the LC-MS/MS method. 

The first mass analyser separates the ions produced in the source. The primary ion is selected and focused into the reaction cell. In the cell, the primary ion beam collides with an inert gas, such as helium, argon or nitrogen, resulting in collision induced dissociation (CID) or collislonally activated dissociation (CAD). The fragment ions produced in the collision cell are mass analysed by the second mass analyser and recorded. This secondary mass spectrum provides a fingerprint of the primary ion beam. 

Many of the radicals formed will recombine to form water and the protons and hydroxide ions eventually neutralise one another. Thus, the ultimate products of water radiolysis (within a ns) in an argon or nitrogen saturated solution are given in reaction 8.10 with the G values shown in parentheses [17, 21]. 

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