Analysis of polycyclic aromatic hydrocarbons by liquid chromatography/tandem mass spectrometry using atmospheric pressure chemical ionization or electrospray ionization with tropylium post‐column derivatization

Abstract

Polycyclic aromatic hydrocarbons (PAHs) with four to six rings are potent carcinogens. This study analyzed ten of the sixteen US EPA priority PAHs using reversed-phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) in selected reaction monitoring mode with two ionization sources: positive atmospheric pressure chemical ionization (APCI+) or positive elecrtrospray ionization (ESI+) with tropylium post-column derivatization. Several factors were investigated, including mobile phases, stationary phases of columns and chromatographic temperature, to determine how optimal separation and sensitivity might be achieved. Methanol used as an organic mobile phase provided better sensitivities for most PAHs than acetonitrile, although some PAHs co-eluted. Acidic buffers did not increase analyte signals. Use of Restek Pinnacle II PAH columns (250 x 4.6 mm or 250 x 2.1 mm, 5 microm) with water/acetonitrile gradient at 27 degrees C made possible a good separation of the ten analytes. [M]+. were the best precursor ions in both APCI and ESI, although fluoranthene could not be detected in ESI mode when tropylium post-column derivatization was performed. [M-28]+ and [M-52]+ were the major product ions of PAHs after collision-induced dissociation, a result of neutral losses of C(2)H(4) and (C(2)H(2))(2), respectively. Chromatographic separation for PAH isomers was crucial because the mass spectra were so similar that even MS/MS could not distinguish them from each other. The recoveries of sample preparations of PAHs spiked onto air-sampling filters ranged between 77.5 and 106% with relative standard deviations between 1.1 and 15.9%. This method was validated by analyzing NIST SRM 1649a (urban dust), producing results comparable with the certified PAH concentrations. The detection limits using APCI and ESI interfaces, defined as three times the noise levels, ranged between 0.23 and 0.83 ng and between 0.16 and 0.84 ng of on-column injection, respectively.

Condensed Phase Membrane Introduction Mass Spectrometry with Direct Electron Ionization: On-line Measurement of PAHs in Complex Aqueous Samples

“…There is significant value in the rapid, quantitative prescreening of samples prior to speciated measurements with standard methods such as solid phase microextraction followed by GC-MS [17], allowing the targeted analysis of contaminated samples and exclusion of prescreen non-detects, saving time and reducing overall cost. As future alternatives for speciated and unbiased direct PAH measurements in complex, real-world samples, high resolution mass spectrometry may be used to mitigate nominal mass isobaric interferences for other matrix components [34], chemical ionization (CI) approaches could affect PAH isomer differentiation [35], and MS/MS used to differentiate alkylated PAHs [24].…”

“…The Blades group has been using dopant assisted atmospheric pressure photoionization (DA-APPI) strategies [22], Song et al employed dopant assisted APCI using chlorobenzene for the successful ionization of PAHs [23], and as another approach, Lien and co-workers coupled ESI with post column derivatization strategies [24]. In contrast, it is well known that PAHs are excellent analytes for mass spectral detection using electron ionization (EI).…”

Detection and Monitoring of PAH and Oxy-PAHs by High Resolution Mass Spectrometry: Comparison of ESI, APCI and APPI Source Detection

“…Yet, ESI can also be used for the detection of nonpolar compounds when ionization is favored using additives like silver [6] or tropylium [7,8]. The original work using silver cationization was performed by Hand et al [6] in solid phase using secondary ion mass spectrometry (SIMS).…”

“…For instance, APCI is used for the detection of high molecular mass PAHs [14]. Yet, it is preferentially used coupled to high performance liquid chromatography (HPLC) for PAH quantification [8,15,16].…”

Off-line solid-phase extraction procedure for the determination of polycyclic aromatic hydrocarbons from aqueous matrices

“…Different detection devices are used to achieve simultaneously high resolution, sensitivity and selectivity. HPLC has been the selected technique for PAHs determination with several detectors: ulraviolet (UV)-visible (Windal et al 2008;Busetti et al 2006), fluorometric (Okuda et al 2006;Serpe et al 2010;Windal et al 2008;Busetti et al 2006;Williamson et al 2002;Garcia-Falcon et al 2004) and mass spectrometer (Viguri et al 2002;Lien et al 2007). However, UV detection yields a sensitivity and selectivity lower than that of fluorometric detection.…”