Liquid chromatography–atmospheric pressure laser ionization–mass spectrometry (LC-APLI-MS) analysis of polycyclic aromatic hydrocarbons with 6–8 rings in the environment

Abstract

A method has been developed for the sensitive and rapid analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental samples using liquid chromatography time-of-flight mass spectrometry as well as the selective atmospheric pressure laser ionization (APLI) process (LC-APLI-MS). Upon analyzing 34 PAHs, the limits of detection of this method were found to range from 0.008 to 1.824 pg (0.024 pg for benzo[a]pyrene). The method therefore provides 30-fold to 5,400-fold increased sensitivity compared with the established GC-MS technique. This LC-APLI-MS method was optimized for higher molecular weight PAHs (C-C PAHs with 6-8 rings), which are difficult to detect or cannot be detected by GC-MS. Using the LC-APLI-MS method, various 6- to 8-ring PAHs were detected in environmental samples for the first time. After developing the method, it was successfully validated in ruggedness tests. The concentrations determined by the LC-APLI-MS method were in good accord with the certified concentrations in three certified reference materials (contaminated soils and sediments). Upon applying the method to environmental samples, it was found that (1) the presence of dibenzo[a,i]pyrene and dibenzo[a,h]pyrene in urban soil samples could only be detected using LC-APLI-MS (i.e., not GC-MS) due to its high sensitivity, (2) a bituminous coal sample yielded 211 tentative peaks from aromatic compounds in the C-C range, and (3) eleven of those compounds occurred in different environmental samples in similar patterns. Hence, 6- to 8-ring PAHs occur in solid environmental samples in which other 6-ring PAHs such as indeno[1,2,3-cd]pyrene or benzo[ghi]perylene may also be present. Some of these numerous higher molecular weight PAH compounds could have very high carcinogenic potential, which will need to be elucidated to ensure the reliability of PAH risk assessments.

Photoionization and photofragmentation in mass spectrometry with visible and UV lasers

“…In 2017, they published a study in which polyaromatic hydrocarbons with six to eight aromatic rings were detected in environmental samples using liquid chromatography together with APLI and mass spectrometry. The reported sensitivity was 1000 times higher than in established GC‐MS applications (Thiäner & Achten, ). In the same year, they showed that GC‐APLI‐MS is not only sensitive and selective but also reliable by comparing measurements with certified reference material.…”

Eluent-assisted Nonresonant Multiphoton Ionization of Polycyclic Aromatic Hydrocarbons in a Liquid Chromatograph-mass Spectrometer

“…We reveal that the fragmentation-and background-free 87 detections by APLI 8,16 are also possible with a sub-…”

“…Since the laser power 45 was stable enough during the experiments, the fluctuation of 46 the ion signal was satisfactorily small. However, the limit of 47 detection was far from that achieved by the established 48 APLI methods8,16 applied for real environmental samples.49 For example, the limit of detection of PAHs achieved by 50 APLI with a time-of-flight MS was on the order of tens of 51 femtograms. 16 The unfavorable detection limit of the present 52 results was attributed to the very small volume of primary 53 ionization as well as the small cross section of multiphoton 54 ionization.…”

“…The 36 mass spectra of anthracene obtained by APCI (Figure S2a) 37 included ions that originated from anthracene, eluent, and 38 presumably impurities, while that obtained by APLI (Figure 39S2b) included only the ions of anthracene. The 40 fragmentation-and background-free features of APLI8,16…”

Analysis of polycyclic aromatic hydrocarbons by capillary electrochromatography by using capillary columns packed with polycyclic‐aromatic‐hydrocarbon‐specific particles

“…The conventional analysis methods for polycyclic aromatic hydrocarbons are of diversity from common separation technologies alone such as GC , HPLC and CE , and typical detection techniques alone such as UV and MS detection to hybrid methodologies combining separation and detection technologies such as GC–MS and HPLC–MS . Of these methodologies, GC–MS is prevailing because of its inherent merits in highly efficient and sensitive analysis of volatile and weakly polar PAHs.…”