LCMS-IT-TOF
Liquid Chromatograph Mass Spectrometer


Ionization Options (APPI, APCI)

The LCMS-IT-TOF adopts the widely used ESI method for ionization, but the APPI (Atmospheric Pressure Photoionization) and APCI (Atmospheric Pressure Chemical Ionization) methods have been added to provide more ionization options for low polarity substances. APPI (Atomospheric Pressure Photoionization) is ionization in which samples are ionized using ultraviolet light. APCI (Atmospheric Pressure Chemical Ionization) is ionization in which the analytical sample is subjected to a corona discharge. APPI achieves good ionization with low to moderate polarity compounds, while APCI is suitable for moderately polar substances, so further expansion of LCMS-IT-TOC applications can be expected using these ionization methods. Selection of the ionization method is based on the sample properties.

APPI-ITTOF (Atmospheric Pressure Photoionization Kit for LS-IT-TOF: APPI + APCI)

  • APPI, APCI, APPI/APCI combination modes are supported.
  • APPI employs ultraviolet light, while APCI achieves ionization using the ion - molecule reaction with the reactant ion (solvent origin).
  • For analysis of low to moderately polar compounds (polycyclic aromatics, some mycotic toxins, etc.)
  • Instrument control and data processing with LCMSsolution software for LCMS-IT-TOF.

APCI-ITTOF (Atomospheric Pressure Chemical Ionization Kit for LCMS-IT-TOF)

  • Supports APCI.
  • 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 APPI and APCI Ionization Methods

Atmospheric Pressure Photoionization (APPI)

This is a new ionization method in which the sample is ionized using ultraviolet light. The APPI method excels in high sensitivity ionization of low polarity compounds. The APCI heater and nebulizer are used to vaporize the sample. (Ionization by a combination of APPI and APCI is also possible using simultaneous UV radiation and the corona discharge.)

Direct APPI

If the analytical target ionization energy is lower than the photon energy, the target ion M+ that was ionized due to the photons receives a proton from the hydrogen in the solvent, to become (M+H)+.

Sensitivity can sometimes be increased by adding a compound called a dopant, which has lower ionization energy than the analytical target.

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.

Measurement Example

MTDATA [4,4',4"-tris (3-methyl-phenylphenylamino) triphenylamine] is a typical material used as an organic EL element. Using the APPI mode, the observed base peak was the molecular ion M+, while in the APCI mode, it was the protonated molecule [M+H]+. It was possible to identify it as MTDATA based on each of the accurate masses. Using APCI, m/z 530.2628, 607.3000 and 698.3422 were observed as cleavage fragmentation ions of MTDATA, while only the molecular ion was observed with APPI, without any cleavage occurring.

For Research Use Only. Not for use in diagnostic procedures.

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