Differentiation of isomeric polyaromatic hydrocarbons by electrospray Ag(I) cationization mass spectrometry.
Abundant Ag(I)-cationized complexes of 13 polyaromatic hydrocarbons (PAHs), [Ag+PAH](+) and [Ag+2(PAH)](+), were readily generated by electrospray ionization (ESI). In-source collision-induced dissociation (CID) of the [Ag+2(PAH)](+) complex yielded the monomer complex [Ag+PAH](+), which fragmented further to yield the radical molecular ion [PAH](+.). Based on significant differences in relative intensities of [Ag+2(PAH)](+), [Ag+PAH](+) and [PAH](+.), isomeric PAHs can be differentiated. The [PAH](+.)/[Ag+PAH](+) ion intensity ratio was found to increase with decreasing ionization potentials (IPs) of PAHs. The ratio was significantly different for the isomeric PAHs studied over a wide range of PAH concentrations (1.6-100 nmol/mL), and showed good measurement reproducibility; the coefficient of variation of inter-day measurements was in the range 3-12% for four representative PAHs (n = 5). Detection limits for phenanthrene, pyrene, chrysene and benzo[a]pyrene, in the form of the monomer complexes [(107)Ag+PAH](+) and measured in the selected-ion monitoring (SIM) mode, were 0.31, 0.63, 0.16 and 1.25 pmol/5 microl injection, respectively (S/N ratio approximately 2-3).
Ming Ng
Kwan
K
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
Ling Ma
Ngai
N
Wai Tsang
Chun
C
D002412:Cations / Q000737:chemistry; D007536:Isomerism; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis* / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D002412:Cations; D011084:Polycyclic Aromatic Hydrocarbons; D012834:Silver