Agilent Triple Quadrupole MS and Sensitivity 3
LC/MS ion sources
Agilent 6400 Series Triple Quad LC/MS Concepts Guide 53
APPI (Atmospheric Pressure Photo Ionization)
For analysis of compounds that ionize poorly by ESI and APCI,
the atmospheric pressure photoionization (APPI) source
provides a useful alternative. It combines Agilent’s proven
orthogonal spray nebulization and counterflow drying gas with
innovative photoionization from Syagen Technology. The
long-lasting krypton lamp emits photons at energy levels high
enough to ionize many large classes of compounds, but low
enough to minimize the ionization of air and common HPLC
solvents. Relatively low ionization energy means the APPI
source causes minimal fragmentation and generates mostly
molecular ions and protonated molecules.
APPI may ionize compounds that do not ionize well by ESI or
APCI, such as Polyaromatic Hydrocarbons (PAHs). Also, APPI
may provide better overall sensitivity for some compounds than
either ESI or APCI. Some examples of these compounds are
Tetrahydrocannabinol (THC), Benzoic acid, and fat soluble
vitamins. APPI may provide better sensitivity at lower flow
rates than APCI. Reproducibility data indicates APPI is robust
and highly reproducible.
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