Andres D. Campiglia

Polycyclic aromatic hydrocarbons (PAHs) of molecular mass (MM) 302 Da comprise numerous structural isomers that are of high concern for human health. Because of their multiplicity, low abundance in the environment, and limited availability of authentic standards, their occurrence, composition, and environmental health risk remain not well characterized. Here we extend the characterization of MM 302 Da PAH isomers in combustion-related particulate matter with the addition of four newly synthesized and previously unidentified MM 302 Da isomers: dibenzo[ a , l ]fluoranthene (DBalF), dibenzo[ b , l ]fluoranthene (DBblF), dibenzo[ a , j ]fluoranthene (DBajF), and naphtho[2,1- j ]fluoranthene (N21jF). Using a coupled high-performance liquid chromatography/gas chromatography-mass spectrometric system with a 50% phenyl methylpolysiloxane stationary phase, 24 MM 302 Da isomers were annotated in four Standard Reference Materials, SRM 1648a, SRM 1649b, SRM 1650b, and SRM 2975, and in four combustion-related particulate matter samples consisting of two traffic-impacted filters and two laboratory-generated combustion samples. Three of the four previously unidentified compounds, DBalF, DBajF, and N21jF, were chromatographically resolved and quantified for the first time in these samples. Quantitative analysis of nine MM 302 Da PAHs (∑MM302Da) showed that these compounds accounted for roughly 0.66–4.1% of the total mass for 50 PAHs. The previously unidentified isomers were recurring but generally minor contributors to the ∑MM302Da burden, with N21jF representing 8–14%, DBalF typically 6–10% (but 23% in SRM 2975), and DBajF varying between 1 and 5%. These results demonstrate both the ubiquity and compositional variability of MM 302 Da PAHs in combustion-derived particulate matter and provide new reference data for analytical investigations of MM 302 Da PAHs. Graphical abstract

When high-performance liquid chromatography (HPLC) is used for the analysis of polycyclic aromatic hydrocarbons (PAHs) in complex samples, further examination of HPLC fractions is recommended to confirm PAH assignments solely based on retention times. Gas chromatography–mass spectrometry (GC-MS) has been particularly relevant in the unambiguous determination of PAHs with remarkably similar retention times. The combination of HPLC and GC requires lengthy analysis times to ensure proper assignments. This article presents an approach for the analysis of co-eluted PAHs with no need for further chromatographic separation. Benzo[a]pyrene (BaP) and dibenzo[a,l]pyrene (DBalP) were directly determined in a co-eluted HPLC fraction via room-temperature fluorescence excitation–emission matrices (RTF-EEMs). RTF-EEMs can be recorded in a matter of seconds with a spectrofluorometer equipped with a multichannel detection system. The spectral overlapping of BaP and DBalP was resolved using parallel factor analysis (PARAFAC). The analytical advantages of this approach were demonstrated with the trace analysis (ng/mL) of these two PAHs in pre-concentrated tobacco extracts.

Polycyclic aromatic hydrocarbons (PAHs) represent one of the most extensive classes of known carcinogenic and genotoxic compounds widely distributed across the globe. Particularly relevant to ecotoxicological studies is the possible presence of PAHs with molecular weight (MW) 302 Da. Since the toxicity of 302 Da PAHs differs significantly from isomer to isomer, understanding their relative toxicity is essential for assessing their potential risks to human health. This study investigates the toxic effects of micromolar concentrations of four HMW-PAHs isomers of MW = 302 Da, namely dibenzo(b,l)fluoranthene (DB(b,l)F), dibenzo(a,j)fluoranthene (DB(a,j)F), dibenzo(a,l)fluoranthene (DB(a,l)F) and naphtho(1-2j)fluoranthene (N(1-2j)F), upon exposure and metabolic activation in HepG2 cells. Appropriate assays were selected to investigate their potential to disrupt cellular viability and to induce cytotoxicity, apoptosis/necrosis, genotoxicity, and oxidative stress with DNA damage. After 48 h of exposure time, DB(a,l)F was the only isomer to reduce cellular viability in a concentration-dependent manner. In all cases, apoptosis was the main mechanism of HepG2 cell death, which could be induced by the significant DNA damage and an increase in 8-hydroxy-2′-deoxyguanosine (8-OHdG) adduct level formation. The highest concentrations of DB(a,l)F tested exhibited the greatest potential to induce HepG2 DNA damage and 8-OHdG formation. Altogether, these facts demonstrate that the distinct arrangements of the atoms in HMW-PAHs isomers can impact on their toxic potential and that DB(a,l)F was the most toxic isomer evaluated in this study. These results shed light on the importance to thoroughly characterize MW302 PAHs to substantiate their human and environmental risk assessments.

Fluorescence spectroscopy is an attractive candidate for analyzing samples of nylon. Impurities within the polymers formed during the synthesis and processing of nylons give rise to the observed fluorescence, allowing for nylons to be analyzed based on their impurities. Nylons from the same source are expected to display similar fluorescence profiles, and nylons with different fluorescence are expected to be from different sources. This paper investigates an important case where different nylons displayed similar fluorescence, preventing easy discrimination. Samples of Nylon 6 and Nylon 6/12 had visually indistinguishable excitation–emission matrices (EEM), excitation spectra, fluorescence spectra, and synchronous fluorescence spectra at larger Δλ. By collecting synchronous fluorescence spectra at smaller Δλ, additional features in the fluorescence profiles were identified that allowed for some discrimination between the two nylons. Combining the EEM and synchronous fluorescence data with chemometric algorithms provided a clearer differentiation between the two nylons. parallel factor analysis, principal component analysis, and common dimension partial least squares (ComDim-PLS) showed two distinct clusters in the data, with ComDim-PLS providing the greatest distinction between the clusters. The loadings revealed the variables of interest to the ComDim-PLS were the 400 nm and 335 nm bands for all synchronous fluorescence spectra, the 460 nm and 310 nm bands for the Δλ = 20 nm and Δλ = 30 nm synchronous fluorescence spectra, and the 440 nm band for the Δλ = 20 nm synchronous fluorescence spectra. The linear discriminant analysis performed with the PLS data yielded a classification accuracy of 95% with the EEM data and 100% with the synchronous fluorescence data, displaying the power of this technique to differentiate two different nylons with visually indistinguishable fluorescence spectra.

Microplastics have garnered an infamous reputation as a sorbate for many concerning environmental pollutants and as a delivery vehicle for the aquatic food chain through the ingestion of these contaminated small particulates. While sorption mechanisms have been extensively studied for polycyclic aromatic hydrocarbons, polycyclic aromatic sulfur heterocycles (PASHs) have not been investigated, partly due to their low concentrations in aquatic ecosystems. Herein, an analytical methodology is presented for the analysis of dibenzothiophene, benzo[b]naphtho[1,2-b]thiophene, benzo[b]naphtho[2,1-b]thiophene, benzo[b]naphtho[2,3-b]thiophene, chryseno[4,5-bcd]thiophene and dinaphtho[1,2-b:1′,2′-d]thiophene at relevant environmental concentrations based on solid phase extraction and high-performance liquid chromatography. The sorption uptake behavior and the sorption kinetics of the three benzo[b]napthothiophene isomers were then investigated on nylon microplastics to provide original information on their environmental fate and avoid human contamination through the food chain. The obtained information might also prove relevant to the development of successful remediation approaches for aquatic ecosystems.

Recent research has demonstrated the unambiguous positive effects of active learning in a variety of college-level courses. We report the implementation and assessment of a 50 minute active-learning in-class activity to conceptualize light absorbance, reflectance, and transmittance, coupled with a writing-to-learn exercise. The activity is suitable in a classroom setting using portable hand-held sensors and samples, including textiles and food-dye solutions. The assessment of the activity included a quasi-experimental design, in which 116 students in an introductory university chemistry course completed the activity, with outcomes compared to a different section, including 322 students, without the active-learning exercise. To determine the efficacy of the activity, students’ written reports and exam assessment items relating to reflectance, transmittance, and absorbance were evaluated. With the assessment questions showing statistically significant improvement, it was concluded that the hands-on activity was effective in helping the students better understand the relationships among the three properties of light.