Application of the effects of solvent and dissolved oxygen on the determination of benzo[a]pyrene by constant-wavelength synchronous spectrofluorimetry in smoke-flavouring

This work studies the effects of solvent and of dissolved oxygen in the determination of benzo[a]pyrene (BaP) by constant-wavelength synchronous spectrofluorimetry in smoke-flavour agents, as confirmation and quantification techniques. The wavelength of the most intense peak at the optimum excitation-emission wavelength interval (20 or 110 nm in most of nine solvents) varied by up to 5 nm, and the detection and quantification limits by a factor of up to 30. The best quantification limit was obtained with DMSO (0.09 mug l(-1)). The deoxygenation of the analyte solution decreased detection and quantification limits, by a variable factor (8-1.13 in the case of n-hexane and DMSO, respectively).     

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.     

Determination of Benzo[a]pyrene in smoking-flavour agents (water-soluble liquid smoke) by second derivative constant-wavelength synchronous spectrofluorimetry

We have developed a simple, rapid, inexpensive method for the determination of benzo[a]pyrene (BP, a known carcinogen) in smoking-flavour agents (water-soluble liquid smoke; WSLS). After purification of the WSLS by a single passage through a Sep Pak C18 Plus cartridge, BP in the hexane eluate was determined by second derivative constant-wavelength synchronous spectrofluorimetry. Method precision (RSD < 6%) and recovery ( approximately 92%) were satisfactory, and the detection and quantification limits (1.05 and 2.28 mug kg(-1) respectively) indicated that the current maximum permissible concentration of BP in smoke flavourings (10 mug kg(-1)) can be monitored by this method.     

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 pyrene and benzo(a)pyrene residues in water by derivative synchronous solid-phase spectrofluorimetry

Benzo(a)pyrene (BaP) and pyrene (Pyr) are two polycyclic aromatic hydrocarbons (PAHs) showing native fluorescence in solution. Both compounds have been determined in water at trace levels by solid-phase spectrofluorimetry, in which BaP and Pyr are fixed on Sephadex G-25 gel and the relative fluorescence intensity is measured after the system is packed in a 1-mm silica cell. First-derivative synchronous spectra obtained at =38 nm were used to determine BaP and Pyr in the presence of other potentially interferent PAHs. The spectral characteristics of the PAHs-gel system are described, the applicable concentration ranges being 0.4–2.5 ng/ml for BaP and 0.7–4.5 ng/ml for Pyr. The relative standard deviations were 1.1% and 1.4% for BaP and Pyr respectively. The detection limits were 0.04 ng/ml for BaP and 0.1 ng/ml for Pyr. The method was applied to the analysis of both compounds in water at trace levels and a recovery study on tap, natural and sea waters was carried out.     

Micelle-sensitized constant-energy synchronous fluorescence spectrometry for the simultaneous determination of pyrene, benzo[a]pyrene and perylene.

The use of micellar media in constant-energy synchronous fluorescence spectrometry has been proposed. The influence of some aqueous micellar systems on the determination of pyrene, perylene and benzo[a]pyrene has been investigated. The presence of these micellar systems allows their determination in aqueous media, thus avoiding the use of an organic solvent, and greatly enhances the fluorescence signals. The combination of a constant-energy synchronous scanning technique and a micellar system provided a single spectrum for the simultaneous identification and quantitative determination of the three polycyclic aromatic hydrocarbons (PAHs). Further there was no energy transfer among them, making the measurement simple and fast. A constant-energy difference of 2800 cm(-1) was selected. The analytical characteristics of the proposed method in the presence of anionic micelles of sodium dodecylsulfate (SDS) were studied. The detection limits were at a level of ng ml(-1). Analysis of water samples from two different origins spiked with known amount of pyrene, perylene and benzo[a]pyrene also gave satisfactory results, and total average recoveries were greater than 97.1%.     

The Electronic Structure of Azuleno[1,2,3-cd]phenalene and Azuleno[5,6,7-cd]phenalene,a Comparison

The photoelectron (PE.) spectra of azuleno[l, 2, 3-cd]phenalene ( 1 ) and azuleno- [5,6,7-cd]phenalene( 2 ) have been recorded. The first five bands of both compounds could be assigned to transitions corresponding to removal of electrons from 4a₂, 6b₁, 5b₁, 3a₂ and 4b_l orbitals. This assignment is based mainly on a comparison between the observed ionization potentials and orbital energies calculated in a HMO and a PPP model. The UV./VIS. polarized absorption spectrum of 1 in the region 10000–45000 cm^?1 has been measured by means of the stretched film technique. The measurements were performed in polyethylene sheets at 77°K. Several bands could be assigned to π* ← π transitions calculated by a PPP-CI method. A comparison between the electronic structures of 1 and 2 is made by means of a simple HMO diagram.     

Development of a micro dual beam fluorometric detector specific for microchip analysis of benzo[a]pyrene and benzo[k]fluoranthene in diesel exhaust particulate samples

We developed a device and some systems for detecting benzo[a]pyrene (B[a]P) and benzo[k]fluoranthene (B[k]F). The device uses a UV light-emitting diode that emits light with a wavelength of 370 nm and a violet laser diode that emits light with a wavelength of 395 nm as excitation light sources. The detection method is based on the following observation: characteristic fluorescence is emitted from both B[a]P and B[k]F, with intensities up to 10 times greater than those from 22 other polycyclic aromatic hydrocarbons (PAHs). The excitation and emission wavelengths for fluorescence from B[a]P and B[k]F are 370 and 429 nm, and 395 and 429 nm, respectively. Further, we calculated their concentrations in diesel exhaust particles by means of two calibration curves determined using a mixture of 24 PAHs. The detection limits of the proposed device with a microchip are 5.58 microg L(-1) for B[a]P and 6.03 microg L(-1) for B[k]F. We applied this method to analyze B[a]P or B[k]F contained in three types of diesel exhaust particles, and the results agreed well with those obtained by liquid chromatography.     

A novel route from triptycenes to a dibenzo(Hafner's hydrocarbon), benz[a]indeno[1,2,3-cd]azulene

Triptycenes carrying a leaving group at one of the bridgehead carbons afforded the title compound in good to moderate yields when irradiated with a low-pressure Hg lamp. The tropylium ion and the strong CT-complexes of the hydrocarbon were prepared.     

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.     

1H NMR spectra of benzo[b]furan,benzo[b]thiophene and benzo[b]selenophene oriented in a lyotropic mesophase

The proton nuclear magnetic resonance spectra of benzo[b]-furan, -thiophene and -selenophene oriented in a potassium laurate lyotropic liquid crystal have been analyzed. Geometrical information has been obtained and compared to previous thermotropic results and various hypothetical models.     

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.     

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 luminescence immunoassay test method for determining benzo[a]pyrene in natural water

A test method is developed for determining benzo[a]pyrene in natural water, based on the use of a polyethylene filter (frit) with adsorbed specific antibodies, placed within a transparent column. In passing a test solution, the analyte is adsorbed on the frit similarly to the process implemented in immunoaffinity preconcentration. The added conjugate of a labeled analyte takes the remained vacant binding sites of antibodies. Luminescent semiconductor nanoparticles (quantum dots) CdSe/ZnS, used as labels, enable visual determination under irradiation with UV light. The limit of detection for benzo[a]pyrene in water is ~0.5 ng/mL.     

Room-temperature excitation-emission phosphorescence matrices and second-order multivariate calibration for the simultaneous determination of pyrene and benzo[a]pyrene

The present article describes the simultaneous phosphorimetric determination of pyrene and benzo[a]pyrene, two highly toxic polycyclic aromatic hydrocarbons, through excitation-emission phosphorescence matrices (EEPMs) and second-order calibration. The developed approach enabled us to determine both compounds at μg L⁻¹ concentration levels without the necessity of applying separation steps, as well as significantly reducing the experimental time. An artificial neural network (ANN) approach was applied to optimize the chemical variables which have an influence on the room-temperature phosphorescence emission of the studied analytes. The present study was employed for the discussion of the scopes of the applied second-order chemometric tools: parallel factor analysis (PARAFAC) and partial least-squares with residual bilinearization (PLS/RBL). The superior capability of PLS/RBL to model the profiles of other potentially interferent polycyclic aromatic hydrocarbons (PAHs) was demonstrated. The quality of the proposed method was established with the determination of both pyrene and benzo[a]pyrene in artificial and real water samples.     

Flow-through sensor based on derivative synchronous fluorescence spectrometry for the simultaneous determination of pyrene, benzo(e)pyrene and benzo(ghi)perylene in water

A flow-through/first derivative synchronous spectrofluorimetric sensor for the determination of PAH has been described. This sensor has been used for the simultaneous determination of PAH mixtures (pyrene, benzo(e)pyrene and benzo(ghi)perylene). Linear calibration ranges between 10 and 500 ng/ml with acceptable precision (repeatability, expressed as relative standard deviation, smaller than 4.6%, and sampling frequency of 12 h^–1) have been obtained. The method has been applied to the determination of the target analytes in spiked water samples with excellent results (recoveries between 94 and 108%).     

Flow-through sensor based on derivative synchronous fluorescence spectrometry for the simultaneous determination of pyrene,benzo(e)pyrene and benzo(ghi)perylene in water

A flow-through/first derivative synchronous spectrofluorimetric sensor for the determination of PAH has been described. This sensor has been used for the simultaneous determination of PAH mixtures (pyrene, benzo(e)pyrene and benzo(ghi)perylene). Linear calibration ranges between 10 and 500 ng/ml with acceptable precision (repeatability, expressed as relative standard deviation, smaller than 4.6%, and sampling frequency of 12 h(-1)) have been obtained. The method has been applied to the determination of the target analytes in spiked water samples with excellent results (recoveries between 94 and 108%).