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.

Due to several polycyclic aromatic hydrocarbons (PAHs) being highly carcinogenic and at the same time occurring at very low environmental concentrations up to the microgram per kilogram range, highly sensitive chemical analysis in various matrices is needed. Here, for the first time, a method using gas chromatography (GC) and atmospheric pressure laser ionization-mass spectrometry (APLI-MS), which is much more sensitive compared to common GC-MS, proved to produce reliable (certified reference materials) and comparable (GC-MS) results. PAHs and selected isomers of alkyl-PAHs were targeted, whereby 53 analytes could be quantified individually; for one pair, the sum had to be calculated. In combination with the selective and sensitive (1+1)-REMPI process of the APLI, limits of detection (LODs) between 5 and 50 fg/μL could be obtained. To prove the reliability of this method, four certified reference materials (SRM1649b urban dust, SRM 1941b organics in marine sediment, BCR 535 fresh water harbor sediment, and ERM CC013a contaminated soil from a former gas plant site) were analyzed. The results were in good accordance with the certified values. In addition, analytical results of three different environmental matrices (bituminous coal, suspended particulate matter from river and pine needles) were compared to values obtained with well-established GC-EI-MS. The results show that this method presents an excellent tool ready-to-use for the analysis of environmental samples with very low PAH content or very low sample amount.

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