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Atmospheric Pressure Photoionization Mass Spectrometry of Fullerenes
journal contribution
posted on 2012-06-19, 00:00 authored by Oscar Núñez, Héctor Gallart-Ayala, Claudia P.B. Martins, Encarnación Moyano, Maria Teresa GalceranAtmospheric pressure photoionization (APPI) was evaluated
for the analysis of fullerenes. An important response improvement
was found when using toluene mediated APPI in negative mode if compared
with other atmospheric pressure ionization (API) sources (electrospray
and atmospheric pressure chemical ionization). Fullerene APPI negative
mass spectra were dominated by the isotopic cluster of the molecular
ion, although isotopic patterns for M+1, M+2, and M+3 ions showed
higher than expected relative abundances. These discrepancies are
explained by the presence of two isobaric ions, one due to 13C and the other due to the addition of hydrogen to a double bond
of the fullerene structure. Triple quadrupole tandem mass spectrometry,
ultrahigh resolution mass spectrometry, and accurate mass measurements
were used to confirm these assignments. Additionally, cluster ions
M+16 and M+32 were characterized following the same strategy. Ions
due to the addition of oxygen and alkyl additions were attributed
to the presence of methanol in the mobile phase. For the fast chromatographic
separation of fullerenes (less than 3.5 min), a sub-2 μm C18
column and isocratic elution (toluene/methanol, 45:55 v/v) was used.
Highly selective-selected ion monitoring (H-SIM) mode (mass resolving
power, >12 500 fwhm) was proposed monitoring the two most
intense isotope ions in the [M]−• cluster.
Method limits of quantitation down to 10 pg L–1 for
C60 and C70 fullerenes and between 0.75 and
5.0 ng L–1 for larger fullerenes were obtained.
Finally, the ultrahigh performance liquid chromatography (UHPLC)-APPI-MS
method was used to analyze fullerenes in river and pond water samples.
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isocratic elutionAtmospheric Pressure Photoionization Mass SpectrometryFullerene APPIisobaric ions13 CC 70 fullerenesAPIresponse improvementultrahigh performanceFullerenesAtmospheric pressure photoionizationisotope ionsmass measurementsalkyl additionspond water samplesTriple quadrupole tandem mass spectrometrymass spectrapressure ionizationMethod limitsclusterultrahigh resolution mass spectrometryfullerene structureC 60pressure chemical ionizationUHPLC
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