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

This study reports studies using electron capture negative ion chemical ionization gas chromatography/mass spectrometry (EC-NICI GC/MS) 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 and can be largely explained by the competitive formation processes of [M]−. and [MH]− ions. The formation of the adduct ion, [M + 15]−, previously attributed to [M + CH3]−, is shown here by using perdeuterated PAH analogues to be a [M + O  H]− ion. For fluorene and acenaphthene, abundant [M + 14]− and [M + 13]− ions can be similarly rationalized to be [M + O  2H]− and [M + O  3H]−. The NICI mass spectrum of (2H10)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 GC/MS as an analytical technique for determining PAHs in fly ash with minimum sample pretreatment.