Polycyclic aromatic hydrocarbons (PAHs) are some of the most common environmental pollutants encountered worldwide. Eco-toxicological studies attribute a significant portion of the biological activity of PAH contaminated samples to the presence of high molecular weight PAHs (HMW-PAHs), i.e. PAHs with molecular mass (MM) greater than 300 Da. The research presented here focuses on the analysis of PAH isomers of MM 302 Da. This is not a trivial task. There are 23 isomers with MM302Da available to commercial and academic researchers. Many of them are difficult to separate in the chromatographic column and have virtually identical fragmentation patterns. The selectivity of HPLC absorption and fluorescence detectors is modest for resolving co-eluting isomers. Previous work in our lab demonstrated the potential of laser excited time-resolved Shpol'skii spectroscopy (LETRSS) for the analysis of 302 Da isomers in HPLC fractions. The main limitation of the technique was instrumental and due to the narrow range of excitation wavelengths of the tunable dye laser used for sample excitation. Herein, we remove this limitation with an optical parametric oscillator (OPO)- based wavelength tuning laser that covers the whole excitation range of 302 Da isomers. It is possible no w to excite each isomer at its excitation wavelength for maximum fluorescence emission and reach limits of - 1 detection at the parts-per-trillion level (pg.mL ). The excitation bandwidth of the OPO laser (0.2 nm) is a good match for the narrow excitation spe ctra of 302 Da isomers in n -octane. This feature, associated to unique vibrational fluorescence profiles and lifetime decays, allows for the unambiguous identification of co-eluting isomers in RPLC fractions. The same is true for their quantitative analysis in coal tar samples.

Santos, S.M., Nascimento, D.C., Costa, M.C., Neto, A.M.B., Fregolente, L.V., 2020. Flash point prediction: Reviewing empirical models for hydrocarbons, petroleum fraction, biodiesel, and blends. Fuel 263, 116375.

http://www.sciencedirect.com/science/article/pii/S0016236119317296 Flash Point (FP) of fuels is essential to determine the requirements for transportation and storage temperature. FP may be a restriction for incorporating light fractions into final products; therefore, accurate prediction models are necessary. However, finding the most accurate prediction model might be a challenge due to the high variety of methods. Hence, we reviewed empirical correlations, the simplest approach to predict FP of pure hydrocarbons, petroleum fractions, blends and biodiesel-FAME once it does not require complex calculation and known composition. Those correlations originally adjusted for pure hydrocarbons were extended to predict FP of petroleum fractions and, vice-versa, to verify the possibility of extension of the models. In addition, empirical models based on blending indexes were tested to predict FP of blends of diesel-biodiesel and hydrocarbons, which were also compared to Liaw's model. The empirical models were assessed using experimental data from literature and from Brazilian refineries. As a result, there is not only one reasonable method for FP estimation of those compounds. It depends on the type of hydrocarbons, range of FP, and ideality and volumetric fraction for blending systems. In addition, we obtained a reasonable result for biodiesel FP prediction from specific vegetable oils by applying kinematic viscosity with AAD=4.14K. For petroleum fractions (distillation range from 340 K to 505 K), unexpectedly, a method firstly developed for pure compounds presented the most sati sfactory performance with AAD=8.11K. Finally, we developed a new model to estimate flash point of Brazilian diesel fractions S500 with AAD=2.11K.

Sanz-Robinson, J., Williams-Jones, A.E., 2020. The solubility of Nickel (Ni) in crude oil at 150, 200 and 250 °C and its application to ore genesis. Chemical Geology 533, 119443.

http://www.sciencedirect.com/science/article/pii/S0009254119305728 The very low solubility of Ni in saline brines and the correspondingly high concentration of Ni in some crude oils raise the possibility that liquid hydrocarbons may be the ore fluids for black-shale-hosted Ni deposits. To test the feasibility of this hypothesis, Ni wires were reacted with three crude oils of differing composition at 150, 200 and 250 °C for up to 30 days, and the concentration of Ni in the oil determined. At 150 °C, Ni concentrations in the three oils remained relatively low. Above 200 °C, however, Ni concentrations were elevated and correlated positively with the thiol content of the oil. Our most thiol-rich oil dissolved 217 ± 40.4 ppm Ni after 30 days at 250 °C. X-ray photoelectron spectroscopic (XPS) analyses performed on the residual oil coating the Ni wires after reaction independently corroborate the conclusion that Ni has a strong chemical affinity for thiols in crude oil. In crude oils with no thiols, the Ni reacted with other sulfur compounds (potentially sulfonic acids) to form thiols. Significantly, our XPS analyses show that iron (Fe) from the oil was