Effects of cluster formation on spectra of benzo[a]pyrene and benzo[e]pyrene

Absorption and fluorescence emission spectra of the polycyclic aromatic hydrocarbons benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) in solution and adsorbed on silica have been obtained and compared to examine the spectroscopic effects of clustering. Molecular mechanics calculations with the UFF potential were done to optimize monomer, dimer and trimer geometries, and energy differences were determined by MP2/6-31G* calculations. Fluorescence emission spectra of adsorbed BeP and BaP display a red shift that progresses with increased loading, and the two differ in their photodegradation kinetics. The experimental and theoretical results are found to be consistent.     

Reinvestigation of the jutz synthesis of benzo [e] pyrene and benzo [a] pyrene derivatives from benzanthrene

Base-catalyzed reactions of benzanthrene with “vinamidinium salts” ($\text{2a-c}$ ) followed by thermal electrocyclic ring closure are regiospecific affording only benzo [e] pyrene derivatives, contrary to previous claims.     

A convenient new synthesis of benzo[a]pyrene

A convenient new synthesis of the ubiquitous environmental carcinogen benzo[a]pyrene (BaP) is described. In the key step, the method entails Suzuki coupling of naphthalene 2-boronic acid with 2-bromobenzene-1,3-dialdehyde and requires only three steps. It is considerably shorter and simpler than the older methods and provides BaP in higher overall yield.     

Magnetic circular dichroism spectra of benzo[a]pyrene

Magnetic circular dichroism (MCD) and absorption spectra of benzo[a]pyrene have been measured. The absorption spectra have been assigned by comparing the experimental results with the signs of Faraday B terms and transition energies computed by using the Pariser—Parr—Pople SCF-π-MO CI method.     

Second-derivative constant-wavelength synchronous scan spectrofluorimetry for determination of benzo[b]fluoranthene, benzo[a]pyrene and indeno[1,2,3-cd]pyrene in drinking water

The use of derivative constant-wavelength synchronous scan fluorimetry is reported for the determination of three polycyclic aromatic hydrocarbon pollutants in drinking water (linearity range 0.4-4 mug 1(-1)). The limits of detection (LD) and quantification (LQ) (mug 1(-1)) are 0.01 and 0.07 for benzo[b]fluoranthene, 0.03 and 0.12 for benzo[a]pyrene and 0.19 and 0.57 for indeno[1,2,3-cd]pyrene in the presence of three other pollutants, benzo[k]fluoranthene, benzo[ghi]perylene and fluoranthene. The precision (RSD /= 85%) were satisfactory.     

A simple method for the determination of benzo[a]pyrene and benzo[k]fluoranthene in a mixture

Atmospheric particulate matter is routinely analysed for the concentration of the carcinogen benzo[a]pyrene (BaP). Benzo[k]fluoranthene (BkF) has identical spectral characteristics and interferes in the fluorimetric estimation. A simple method for the determination of BaP in the presence of BkF is described. Based on quenching of the fluorescence of BaP by the addition of small amounts of nitromethane, the method can be used for accurate estimation for wide concentration ratios of BaP to BkF ranging from 0.1 to 10.0.     

Measurement of benzo[a]pyrene,benzo[k]fluoranthene and benzo[g,h,i]perylene by ultraviolet spectroscopy

Microchimica Acta - The technique for determining benzo[a]pyrene, benzo[k]fhuoranthene, and benzo[g,h,i]perylene respectively inμg amounts by UV absorption measurements is described. The...     

Determination of benzo[a]pyrene in shale oil-by solid-surface fluorescence

A method has been developed for determining benzo[a]pyrene in shale oil by combining dry-column chromatography, thin-layer chromatography and fluorescence spectrometry. A two-step separation method was employed to isolate benzo[a]pyrene from shale oil. Benzo[a]pyrene was identified and determined by detecting its fluorescence directly from chromatoplates; as little as 0.06 ng can be detected. The limit of detection of benzo[a]pyrene in shale oil is ca. 1.2 ppm and the reproducibility of the method is ±2.6 ppm.     

Light induced interactions of benzo[a]pyrene with carboxylic acids

Abstract The in vitro photochemical behaviour of benzo[a]pyrene (BP) in presence of short and long chain carboxylic acids is studied. The direct irradiation (295–400 or 320–400 nm) of BP in solution in the presence of saturated carboxylic acids destroys more than 70% of this carcinogen in 72 h with a 150 W Xe arc lamp. Consumption of BP alone under similar conditions is less than 10%. The principal product resulting from direct interaction of BP with carboxylic acids is characterized as 6-acyloxybenzo[a]pyrene by means of UV, IR, NMR and mass spectroscopy. The other pathways of destruction may involve polymerization. Saturated fatty acids are shown to favour photoacyloxyation, while unsaturated fatty acids appear to facilitate polymerization of BP. The effect of different factors, such as the carboxylic acid involved, solvent, and wavelength on photoacyloxylation reaction as well as on the consumption of BP is discussed. Photoinduced interaction of BP with carboxylic acids seems to involve radical cation as well as free radicals of the hydrocarbon. Biological properties of BP esters in terms of primary irritancy and carcinogenic activity have also been tested by mouse skin assay. Both long and short chain esters do not show any carcinogenic activity; conversely, long chain esters are shown to be more severe irritants as compared to short chain esters or BP.     

Supersonic jet fluorescence spectrometry of perylene and benzo[a]pyrene

A supersonic jet instrument for fluorescence spectrometry is described. It consists of a high-temperature free expansion nozzle for continuous sample introduction and a vacuum chamber equipped with a high-speed pumping system. Rotationally cooled spectra obtained with the supersonic jet are compared with gas-phase spectra measured at high temperature for perylene and benzo[a]pyrene molecules. Each component of the unresolved band structure in the high-temperature spectra was found to be composed of a rotational congestion of several vibrational bands. For a 1:1 mixture of perylene and benzo[a]pyrene, selective detection is possible by using supersonic jet spectrometry. The detection limit for perylene is 100 ng. The advantage of this technique over other low-temperature spectrometric methods based on Shpol'skii and matrix isolation effects are discussed.     

Oxidized metabolites from benzo[a]pyrene, benzo[e]pyrene, and aza-benzo[a]pyrenes. A computational study of their carbocations formed by epoxide ring opening reactions

A DFT study aimed at understanding structure-reactivity relationships and fluorine substitution effects on carbocation stability in benzo[a]pyrene (BaP), benzo[e]pyrene (BeP), and aza-benzo[a]pyrene (aza-BaP) derivatives are reported. The relative energies of the resulting carbocations are examined and compared, taking into account the available biological activity data on these compounds. O-Protonation of the epoxides and diol epoxides leads to carbocation formation by barrierless processes. Charge delocalization modes in the resulting carbocations were deduced via NPA-derived changes in charges, and fluorine substitution effects were analyzed on the basis of charge density at different carbocation positions. Thus, fluorine substitution at sites bearing negative charge generated inductive destabilization of the carbocation, whereas a fluorine atom at a ring position which presented significant positive charge density produced a less pronounced destabilization due to fluorine p-pi back-bonding. Protonation reactions were also studied for the azaBaPs. In selected cases, the covalent adducts generated via bond formation with the exocyclic nitrogen of cytosine were computed and relative energies and geometries of the resulting adducts were examined.     

Metrological traceability for benzo[a]pyrene quantification in airborne particulate matter

Airborne particulate matter (PM) represents one of the most important sources of urban pollution due to its physical and chemical properties. There is a great concern for PM dangerous effects on human health because particles can deeply penetrate into the respiratory system, carrying the contaminants adsorbed onto their surface. Polycyclic aromatic hydrocarbons (PAHs) are a class of organic contaminants that can be adsorbed onto PM and can have harmful effects on health, due to their particular chemical structure. The International Agency for Research on Cancer (IARC) classified PAHs as potential carcinogenic agents and benzo[a]pyrene (BaP) as carcinogenic to humans. In this paper, the development of a metrologically traceable procedure for the quantification of BaP in airborne PM, performed at the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica—I.N.Ri.M.), is presented. The identification and quantification of BaP in PM samples were carried out by gas chromatography coupled with mass spectrometry (GC–MS). Metrological traceability was established in all the procedure steps, after performing the method validation. Suitable certified reference materials (CRMs) were used both to validate the analytical method and to calibrate the GC–MS. The measurement uncertainty was evaluated by identifying and taking into account all the relevant sources deriving from the whole procedure steps.     

Enrichment of benzo[a]pyrene in vegetable oils and determination by HPLC-FL

We have developed a simple method for the determination of the carcinogen Benzo[a]pyrene (BP) in vegetable oils. The method consists of extraction of the vegetable oil in acetonitrile, concentration to dryness in rotary evaporator and redissolution of the residue in hexane. The purification of the hexane extract was on Sep-Pack Silica Plus cartridges, and the determination of the BP in the isolated extract was by HPLC-FL. Detection and quantification limits were 0.23 and 0.32 μg kg⁻¹ of olive oil, respectively. Recovery (>93%) and RSD (<4%) were satisfactory. When applied to 18 oil samples, BP levels varied from not detected to 1.99 μg kg⁻¹.     

Synthesis and NMR characterization of a dioxa-analog of benzo[a]pyrene: The 1-benzopyrano[6,5,4-mna]-xanthene (1,6-dioxabenzo[a]pyrene)

1,6-Dioxabenzo[a]pyrene, the first dioxa-analog of benzo[a]pyrene, was synthesized from 5-methoxy-1-naphthol in an eight-step reaction involving two peri-heterocyclizations.     

The monomethyl and dimethyl derivatives of benzo[e]pyrene

Convenient syntheses of the previously unknown complete set of six isomeric monomethyl derivatives of benzo[e]pyrene, 1-, 2-, 3-, 4-, 9- and 10-methylbenzo[e]pyrene, are described. Syntheses of 1-, 2- and 3-methylbenzo[e]pyrene were accomplished through reaction of 7H-benzanthrene (or its 1-Me derivative as appropriate) with 1, 3-bis(dimethylamino)trimethinium perchlorate (or its 1-Me derivative) followed by thermal electrocyclic ring closure accompanied by elimination and aromatization. The earlier claim¹⁶ that the analogous isomeric benzo[a]pyrene derivatives are principal products of reactions of this type is disproven. Synthesis of 3,6- and 4,5-dimethylbenzo[e]pyrene are also described. The structural assignments of all mono- and dimethyl benzo[e] pyrene products are supported by high resolution 270 MHz proton NMR spectra; the chemical shifts and coupling constants of all aromatic protons are fully assigned.     

Characterization of antibodies against benzo[a]pyrene with thermodynamic and kinetic constants

Antibodies of a polyclonal antiserum against benzo[a]pyrene were characterized by determining thermodynamic and kinetic constants of the antigen–antibody reaction. Label-free binding assays with optical detection based on reflectometric interference spectroscopy were performed to determine these constants. Different evaluation methods for kinetic measurements were compared. Also, cross-reactivity against two other polycyclic aromatic hydrocarbons, chrysene and pyrene, was checked. The affinity constant between the antibodies and benzo[a]pyrene in homogeneous phase was determined to be K=(5.3±0.3)×10⁷ M⁻¹ which was in the middle of the usual range of antibody affinities. The association rate constant for the reaction at the surface was determined to be (3.8±0.9)×10⁵ M⁻¹ s⁻¹, the dissociation rate constant as (9.7±0.5)×10⁻³ s⁻¹. Different evaluation methods applied to the kinetic measurements led to the same results. This antiserum would be suitable for the selective determination of benzo[a]pyrene in concentrated samples.