Determination of polycyclic aromatic hydrocarbons in coal fly ash using gas chromatography/negative ion chemical ionization mass spectrometry

Abstract

This study reports studies using electron capture negative ion chemical ionization gas chromatographylmass spectrometry (EC-NICI G U M S ) of 21 polycyclic aromatic hydrocaroon (PAH) compounds. The selectivity and sensitivity of these compounds are shown here to be highly dependent on ion source temperature and pressure. Changes in selectivity arise from variations in instrumental parameters and can be largely explained by the competitive formation processes of [MI-' and[M-HIions. The formation of the adduct ion, [M+ 15]-, previously attributed to [M + CH,]-, is shown here by using perdeuterated PAH analogues to be a [M + 0 -HIion. For fluorene and acenaphthene, abundant [M + 141-and [M + 131-ions can be similarly rationalized to be [M+ 0 -2H]and [M+ 0 -3H]-. The NICI mass spectrum of (*HIo)acenaphthene demonstrates that ring proton losses most likely occur. This study also indicates that there is a strong correlation between the NICI response factor and the reported carcinogenic activity of PAHs in the literature. In addition, this work assesses the viability of NICI G U M S as an analytical technique for determining PAHs in fly ash with minimum sample pretreatment. ~~ ~ EXPERIMENTAL Chemicals and ReagentsPAH reference compounds of 95-99% purity were purchased from severai sources: naphthaiene, acena-

Negative ions generated by reactions with oxygen in the chemical ionization source. I. Characterization of gas‐phase and wall‐catalyzed reactions of fluorene, anthracene and fluoranthene

“…Non-reactive buffer gases, like methane, have been used to enhance negative ion formation by electron-capture reactions,3-' ' while reactive reagent gases, like oxygen or nitrous oxide, have been used to promote ionization by ion-molecule reactions.6"'-'8 Using methane as the buffer gas, it has been shown that PAH with calculated electron affinity (EA) values greater than about 0.5 eV produce abundant molecular ions, M -', 3 while PAH with EA values lower than 0.5 eV respond poorly. In some studies, PAH with low EA values have been observed to yield [M -HI-ions that have been attributed to deprotonation by basic species in the buffer gas5, 8 reported when the NICI spectra of PAH have been obtained using non-reactive gases. These ions have been attributed to reactions with either ionic species, generated from buffer gas impurities, or radical species, produced upon ionization of the buffer gas.…”

The Gulf Oil Spill

“…A variety of analytical methods has been used for determining trace concentrations of PAHs in environmental samples (Table 6- Oehme (1983) and Low et al (1986) employed capillary GC coupled with negative ion chemical ionization MS for detecting and differentiating isomeric PAHs (including PAHs on EPA's priority pollutant list). This procedure was successfully used to differentiate the isomers benzolj]fluoranthene and benzo [b]fluoranthene at low ppb levels in complex matrices, such as air particulate matter and coal fly ash.…”

The determination of polycyclic aromatic hydrocarbons in smoked fish by gas chromatography mass spectrometry with positive-ion chemical ionization

“…The LOD for I[cd]P is lower by negative-ion chemical ionization than by positive-ion chemical ionization, but in the same time B[a]A is not detected by negative-ion chemical ionization mass spectrometry. As one can see from Table 2 the Table 6 Electron affinity (EA) of PAH (Low et al, 1986) and methane negative-ion chemical ionization mass spectra of PAH from the present work For the purpose of comparison, the content of PAHs found in various smoked fish products was confronted with data from literature. The levels of PAH in Estonian smoked fish in the present study are lower than those found in smoked fish from Japan (Masuda and Kuratsune, 1971), but show good agreement with results from Canada (Panalaks, 1976), Sweden (Larsson, 1982), Russia (Kim et al, 1999) and Italy (Moret et al, 1999).…”

“…Table 6 summarizes the fragment ions in the methane negative ion chemical ionization mass spectra of the six PAHs compounds studied. Table 5 Proton affinity (PA) of the PAH (Riahi and Sellier, 1998) (Low et al, 1986). The LOD and the LOQ has been established using spiked samples and determined by negative-ion chemical ionization.…”

“…Positive-and negative-ion chemical ionization mass spectrometry with methane, dimethylether, tetramethylsilane, ammonia (Low et al, 1986;Strouk-Pointet et al, 1995;Pointet et al, 1997;Riahi and Sellier, 1998) or a mixture of methane/argon, isobutane/oxygen, nitrogen/nitrous oxide, hydrogen (Brotherton and Gulick, 1986) as reagent gases have been used to differentiate between isomeric PAHs. Negative-ion chemical ionization using carbon dioxide alone or in a mixture with nitrogen and oxygen has been reported (Stemmler and Buchanan, 1989).…”