Determination of the fluorescence properties of polynuclear aromatic hydrocarbons in the vapor phase and adsorbed on solid supports by laser-induced molecular fluorescence

The fluorescence properties (lifetimes and spectra) of anthracene and fluoranthene were found to be independent of temperature in the ranges 80–110°C and 60–95°C, respectively, in vacuum and in helium, nitrogen, and air atmospheres. The fluorescence lifetimes and spectra were also measured for these two compounds individually adsorbed on silica, alumina, magnetite, or hematite. In all cases, the emission profiles for the adsorbed aromatic hydrocarbon were red-shifted with respect to the gas-phase spectra. The fluorescence lifetimes for both anthracene and fluoranthene increased for the different supports in the order alumina < silica < magnetite < hematite.     

Conventional fluorescence spectrometry of polynuclear aromatic hydrocarbons in Shpol'skii matrices at 77 K

A simple fluorimeter assembled from commercial components and its use for the study and application of the Shpol'skii effect on polynuclear aromatic hydrocarbons (PAHs) in n-alkane matrices at 77 K are described. The correlation between the dimensions and geometries of PAHs and their corresponding Shpol'skii solvents is considered. Analytical figures of merit have been evaluated, and the power of the Shpol'skii technique with a conventional fluorimeter in the direct qualitative and quantitative determination of 11 PAHs in mixture is demonstrated. Comparisons with conventional room-temperature fluorescence and laser-excited Shpol'skii spectrometry are also commented upon.     

Magnetic field effects-polarization-resonant synchronous fluorescence spectrometry for simultaneous analysis of polynuclear aromatic hydrocarbons in mixtures

The level and undulation of scattered light can be effectively suppressed by magnetic field effects-polarization-resonant synchronous fluorescence spectrometry. The established technique was used for simultaneous determination of a sample mixture containing fluorene, acenaphthene, anthracene, benzo-[a]-pyrene (B-[a]-P) and perylene. The detection limits were 0.23, 7.90, 0.13, 1.10, 0.0083 ng ml⁻¹ for fluorene, acenaphthene, anthracene, B-[a]-P and perylene, respectively. The relative standard deviations were less than 5%.     

Detection of particulate polycyclic aromatic hydrocarbons by laser-induced time-resolved fluorescence

Summary Laser-induced fluorescence is introduced as an analytical technique for the detection of particle-bound PAHs, which can be found as a result of most combustion processes. A quartz fiber is used to couple the light of a frequency-doubled excimer-pumped dye laser into the sensor head. The fluorescence light is detected using collecting optics, a set of interference filters and a photomultiplier. PAHs in different forms (crystalline, as homogeneous particles and coated on NaCl particles) were investigated. Fluorescence spectra and time-resolved signals, which exhibit characteristic decay times, are presented.     

Determination of polynuclear aromatic hydrocarbons in micellar solution by electrogenerated chemiluminescence

When polarized cathodically in aqueous acetate solution (pH 7.0) containing peroxodisulfate, a micelle-forming surfactant (Brij-35) and a polynuclear aromatic hydrocarbon, an oxide-covered aluminum electrode produces an intense electroluminescence where the emitting species is the micelle-encapsulated hydrocarbon. The detection limit is ca. 10^?8 M for 9,10- diphenylanthracene.     

Determination of polynuclear aromatic hydrocarbons in environmental samples by Micellar liquid chromatography

A method for the separation of polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography using a hybrid micellar mobile phase is described. The detection of PAHs was carried out using the fluorescence method with programmable excitation and emission wavelength. The method is applied to the analysis of several environmental samples (sea water, sediments, limpets, sea worms) and several of these compounds are quantitated at concentration below 70 ng L⁻¹(kg⁻¹) in the original samples.     

Determination of polynuclear aromatic hydrocarbons in water by flotation enrichment and HPLC

A method of concentration and determination of several polynuclear aromatic hydrocarbons (PAHs) in water by flotation enrichment and HPLC is described. Triton X-100 was used as the foaming agent to extract the PAHs from water by passage of nitrogen. Reversed-phase liquid chromatography with coupled fluorescence detection was applied to separate and determine these PAHs. Various factors which may affect the recovery of PAHs from water, including pH, temperature and the concentration of Triton X-100 added, are discussed. This simplified method of concentrating PAHs from water has been applied to determine PAHs in water from Lake Erie. The method has practical value for the determination of PAHs in large volumes of water.     

Analysis for polynuclear aromatic hydrocarbons in working atmospheres by computerized gas chromatography-mass spectrometry

Polynuclear aromatic hydrocarbons in particulate matter from working atmospheres have been analyzed by a glass capillary gas chromatography—mass spectrometer—computer system which has high separation efficiency and is capable of separating and identifying these complex mixtures. More than one hundred polynuclear aromatic hydrocarbons have been identified in samples from a coke plant and an aluminum smelter, including both pure polycyclic aromatic hydrocarbons and compounds where a CH-group is substituted with the hetero atoms oxygen, nitrogen, or sulfur. The occurrence of polynuclear aromatic hydrocarbons in working atmospheres is compared to that in ambient air and emissions from other sources.     

Cryogenic-temperature fluorescence spectroscopy of polynuclear aromatic hydrocarbons of molecular weight 378

Quasi-linear fluorescence spectra were recorded at 63 K from polynuclear aromatic hydrocarbons with molecular weights of 378, consisting of seven cata-condensed benzene rings. The sensitivity of the method used is clearly sufficient for nine well resolved spectra to be recorded, even though the solubility of the compounds is low in most solvents.     

Cryogenic-temperature fluorescence spectroscopy of polynuclear aromatic hydrocarbons of molecular weight 328

Quasi-linear fluorescence spectra of polynuclear aromatic hydrocarbons with a molecular weight of 328 were recorded at cryogenic temperatures. Thirteen of the sixteen compounds studied showed fluorescence spectra with quasilines at 63 K. Of these, six compounds exhibited highly resolved and intense spectra when dissolved in n-hexane.     

Laser fluorimetry of polynuclear aromatic hydrocarbons based on time-resolved fluorescence detection

Three polynuclear aromatic hydrocarbons are quantified from the pre-exponential factor of the fluorescence decay curve, instead of the integrated fluorescence intensity. The slopes of the calibration plots are independent of the oxygen concentration in the solvent as predicted. Deaeration of sample solutions gives lower detection limits (around 10^?10 M); the extent of improvement depends on the fluorescence lifetime.     

Quantitation and identification of polynuclear aromatic hydrocarbons by liquid chromatography and multiwavelength absorption spectrometry

This paper describes the combined use of liquid chromatographic separation with multiwavelength absorption detection for the quantitation and identification of polynuclear aromatic hydrocarbons. Quantiative results are presented for three- and four-component mixtures with complete and partial separation. Qualitative data are presented for a twelve-component synthetic mixture and for extracts from a filter used to collect particulate emissions from a biomass-gasifier system. It is shown that multiwavelength data-processing methods commonly applied to absorption spectra can be applied with significant advantage to second-derivative spectra. Results indicate that significant improvements can be achieved by the use of different wavelength ranges for different components in mixtures. Detection limits for single-component samples varied between 3 and 11 μg l^?1 for eleven hydrocarbons and the scatter about calibration plots for mixtures was in the range of 0.05 to 0.4 μg ml^?1. The identities of all twelve components in the synthetic mixture were confirmed and nineteen components were identified in the sample from the biomass gasifier filter.     

Determination of ultratrace quantities of uranium by laser-induced fluorescence spectrometry

Uranium (1.5–12 ng l^?1) is co-precipitated with calcium fluoride, the precipitate is ignited in air, and the uranium fluorescence induced by a pulsed nitrogen laser is measured. The detection limit is 0.5 ng l^?1 uranium. Iron(III) and lead interfere seriously.     

Determination of polynuclear aromatic hydrocarbons in aerosol by solid-phase extraction and gas chromatography-mass spectrum

The optimum procedures for clean up aerosols in silica solid-phase extraction (SPE) cartridge prior to the analysis of polynuclear aromatic hydrocarbons (PAHs) by gas chromatography–mass spectrum (GC–MS) in selected ion monitoring detection mode have been investigated. The silica SPE cartridge is activated by dichloromethane and hexane, and then dried up by vacuum in SPE instrument for about 5 min. The sample volume loaded on the cartridge is 3 ml and after loading the sample the cartridge was dried in vacuum for 5 min. The PAHs were eluted from the cartridge by 3 ml 20% dichloromethane in hexane. The flow-rate of sample loading and eluting was controlled in about 1 ml min⁻¹. The aerosols collected on the campus of Beijing Normal University from August 2001 to July 2002 have been processed with these optimum procedures and 16 EPA priority pollution PAHs in the aerosols have been quantitatively determined.     

Penetration of mercury-adsorbed phospholipid monolayers by polynuclear aromatic hydrocarbons

The penetration of phospholipid monolayers (dioleoyl lecithin) adsorbed on mercury by polynuclear aromatic hydrocarbons (PAH) is described. The PAH studied were anthracene, phenanthrene, pyrene, benzo[a]anthracene, fluoranthene and perylene. The penetration is monitored by measuring the differential capacitance of the monolayer; the uptake of PAH causes a potential shift (up to ?0.25 V) in the cathodic capacitance peaks. This occurs without displacement of the lipid from the mercury. The differential capacitance is measured by out-of-phase (90°) a.c. voltammetry and rapid cyclic voltammetry. The PAH permeate the mercury-adsorbed lipid layers from dilute aqueous solution; the order of affinity is benzo[a]anthracene > fluoranthrene = pyrene > anthracene = phenanthrene. The rates of penetration vary for the different compounds and depend on their water solubility.     

Determination of polycyclic aromatic hydrocarbons by electron spin resonance spectrometry

The use of electron spin resonance spectrometry with a modern instrument is described for the determination of polynuclear aromatic hydrocarbons (PAHs) down to nanogram levels, after adsorption on calcined silica/alumina. A single PAH or the total number of moles of PAHs can be determined. Implication for liquid chromatography are discussed.     

Determination of basic azaarenes and polynuclear aromatic hydrocarbons in airborne particulate matter by gas chromatography

Polynuclear aromatic hydrocarbons (PAH) and their nitrogen analogs, basic azaarenes, are extracted from samples of airborne particulate matter by toluene with ultrasonic treatment. The basic azaarenes are extracted from the toluene phase with phosphoric acid, re-extracted from the phosphoric acid phase (adjusted to pH 14 with potassium hydroxide) with dichloromethane, and determined by capillary gas chromatography (g.c.) with a nitrogen-sensitive detector. The PAH in the toluene phase are isolated by means of semipreparative high-performance liquid chromatography and liquid-liquid extraction and determined by g.c. with a flame-ionization detector. Eleven basic azaarenes were identified; their concentration were one to two orders of magnitude lower than those of PAH. Results from the determination of the concentrations of basic azaarenes and PAH in the atmosphere in a busy street and in a suburban residential area of Copenhagen are presented and discussed.     

Phosphorimetric determination of polynuclear aromatic hydrocarbons in gasoline

The possibility of determining pyrene, anthracene, and fluorene in gasoline by phosphorimetry at room temperature after the micellar extraction with sodium dodecyl sulfate was examined. It was found that the above polynuclear aromatic hydrocarbons simultaneously present in gasoline can be selectively determined by room-temperature phosphorimetry using different techniques for the excitation and population of the triplet states of luminophore (stationary and pulse excitation and triplet energy transfer). The proposed procedure was verified by gas chromatography with a mass-selective detector.