Liquid Chromatograph Mass Spectrometer
Ionization Options (APCI)
The LCMS-IT-TOF adopts the widely used ESI method for ionization, but the APCI (Atmospheric Pressure Chemical Ionization) method have been added to provide more ionization options for low polarity substances. APCI (Atmospheric Pressure Chemical Ionization) is ionization in which the analytical sample is subjected to a corona discharge. APCI is suitable for moderately polar substances, so further expansion of LCMS-IT-TOC applications can be expected using these ionization method.
APCI-ITTOF (Atomospheric Pressure Chemical Ionization Kit for LCMS-IT-TOF)
- APCI achieves ionization using the ion – molecule reaction with the reactant ion (solvent origin).
- For analysis of moderately polar substances (steroids, lipids, sugars, pesticides, etc.)
- Instrument control and data processing with LCMSsolution software for LCMS-IT-TOF.
Principles and Components of APCI Ionization Method
Atmospheric Pressure Chemical Ionization (APCI)
This is an ionization method in which the sample is ionized using an ion – molecule reaction with a reactant ion. Sample solution is nebulized by the N2 nebulizer gas to form a spray as it enters the heater (at about 400°C), and both sample and solvent molecules are vaporized to a gaseous state. The solvent molecules are ionized by the corona discharge, and stable reactant ions are formed. Protein transfer occurs between these reactant ions and sample molecules (ion – molecule reaction), and the sample molecules either add or lose protons to become ions. This ion – molecule reaction is known to occur in a variety of patterns, such as protein shift reactions, electrophilic addition reactions, etc. Similarly as with ESI, primarily protonated molecules (or deprotonated molecules) are detected, so it is used for analysis of highly lipid-soluble compounds and compounds that do not ionize in solution.
MTDATA [4,4',4"-tris (3-methyl-phenylphenylamino) triphenylamine] is a typical material used as an organic EL element. Using the APCI mode, the observed base peak was the protonated molecule [M+H]+. It was possible to identify it as MTDATA based on the accurate masses. Using APCI, m/z 530.2628, 607.3000 and 698.3422 were observed as cleavage fragmentation ions of MTDATA.