Polycyclic Aromatic Hydrocarbons In Solution Research Articles

Simultaneous quantification of dilute aqueous solutions of certain polycyclic aromatic hydrocarbons (PAHs) with significant fluorescent spectral overlap using total synchronous fluorescence spectroscopy (TSFS) and N-PLS, unfolded-PLS and MCR-ALS analysis

The possibility of simultaneous quantification of dilute aqueous solutions of five polycyclic aromatic hydrocarbons (PAHs) with substantial overlap of fluorescence spectra without preseparation was examined by using total synchronous fluorescence spectroscopy (TSFS) with multivariate methods like N-way partial least square (N-PLS), unfolded-PLS and multivariate curve resolution-alternating least square (MCR-ALS) analysis. The PAHs chosen were anthracene, benzo[a]pyrene, chrysene, perylene and pyrene. Two calibration sets were made using different approaches. Even with significant spectral overlap, the N-PLS, unfolded-PLS and MCR-ALS models were found to be robust for the quantification of all five PAHs in the calibration set where the amounts of PAHs were changed with the fixed relative ratio. The second calibration set, which is relatively difficult to analyse, consisted of samples where amounts of PAHs were changed randomly. It was found that even for this set, predictions were satisfactory. The three calibration models based on N-PLS, unfolded-PLS and MCR-ALS in the second set were relatively more robust for chrysene, benzo[a]pyrene and perylene compared to other PAHs. Root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) and regression parameters were calculated for all the three calibration models. The various parameters show that the combination of TSFS and N-PLS, unfolded-PLS and MCR-ALS analysis can be used for the simultaneous quantification of PAHs in water without any preseparation even when there is substantial overlap of fluorescence.

One-Calibrant Kinetic Calibration for On-Site Water Sampling with Solid-Phase Microextraction

The existing solid-phase microextraction (SPME) kinetic calibration technique, using the desorption of the preloaded standards to calibrate the extraction of the analytes, requires that the physicochemical properties of the standard should be similar to those of the analyte, which limited the application of the technique. In this study, a new method, termed the one-calibrant kinetic calibration technique, which can use the desorption of a single standard to calibrate all extracted analytes, was proposed. The theoretical considerations were validated by passive water sampling in laboratory and rapid water sampling in the field. To mimic the variety of the environment, such as temperature, turbulence, and the concentration of the analytes, the flow-through system for the generation of standard aqueous polycyclic aromatic hydrocarbons (PAHs) solution was modified. The experimental results of the passive samplings in the flow-through system illustrated that the effect of the environmental variables was successfully compensated with the kinetic calibration technique, and all extracted analytes can be calibrated through the desorption of a single calibrant. On-site water sampling with rotated SPME fibers also illustrated the feasibility of the new technique for rapid on-site sampling of hydrophobic organic pollutants in water. This technique will accelerate the application of the kinetic calibration method and also will be useful for other microextraction techniques.

Photochemistry of phenanthrene, pyrene, and fluoranthene in ice and snow

Although polycyclic aromatic hydrocarbons (PAHs) are common pollutants in snow, there is little quantitative data about their rates of photodegradation in this environment. To begin to address this gap, we have measured the degradation kinetics of phenanthrene, pyrene, and fluoranthene on ice, as these are the most abundant PAHs in arctic snow. Frozen aqueous solutions of individual PAHs, with and without added hydrogen peroxide (HOOH) as a source of hydroxyl radical ( OH), were illuminated with simulated sunlight. For all three PAHs, direct photodecay is the main mechanism of degradation, while OH-initiated indirect photodegradation is a minor sink. Rate constants (±1 SE) for direct photodegradation extrapolated to midday, surface snow conditions at Summit, Greenland on the summer solstice are 3.8 (±0.8) × 10 −5, 28 (±3) × 10 −5, and 1.4 (±0.7) × 10 −5 s −1 for phenanthrene, pyrene, and fluoranthene, respectively. Apparent quantum efficiencies for photodegradation with simulated sunlight were 3.8 (±0.8) × 10 −3, 4.3 (±0.5) × 10 −4, and 2 (±1) × 10 −5, respectively. Calculated PAH lifetimes in surface snow under Summit conditions are 1–19 h during mid-summer, but increase to >100 days in the dark winter. While the short photodegradation lifetimes in the summer suggest that there should be no appreciable PAH levels in this season, past measurements at Summit sometimes show significant levels of these PAHs in summer surface snow. This discrepancy is likely due to differences in PAH location between lab samples (where the PAHs are probably in quasi-liquid layers) and real snow (where PAHs are likely primarily associated with particulate matter).

Final report on CCQM-K38: Determination of PAHs in solution

Solutions of known mass fraction of organic analytes of interest are typically used to calibrate the measurement processes used in the determination of these analytes. Appropriate value assignments and uncertainty calculations for these calibration solutions are critical. For the Mutual Recognition Arrangement (MRA) developed by the CIPM, there are numerous Calibration and Measurement Capability Claims (CMCs) published in Category 3 Organic Solutions in the CIPM MRA Appendix C. Additional CMCs in this category are being proposed and reviewed. Evidence of successful participation in formal, relevant international comparisons is needed to support these claims.A CCQM pilot study conducted in 2004 was comprised of three parts: CCQM-P31a Organic Solution—Polycyclic Aromatic Hydrocarbons (PAHs), CCQM-P31b Organic Solution—Polychlorinated Biphenyl (PCB) Congeners, and CCQM-P31c Organic Solution—Chlorinated Pesticides. The results from the CCQM-P31a study are summarized below for the PAHs. After review of the P31a results at the April 2004 Organic Analytical Working Group (OAWG) meeting (Sèvres 2004) and the October 2004 OAWG meeting (Beijing 2004), it was decided to proceed with a key comparison study for PAHs in solution (CCQM-K38) with a concurrent second pilot study for the PAHs in solution (CCQM-P31a.1). CCQM-K38 was conducted during the same time period as a PAHs in soil pilot study (CCQM-P69) coordinated by CENAM and BAM.This Key Comparison study demonstrated a high level of equivalence in capabilities of the participating NMIs to successfully identify and measure five PAHs (phenanthrene, fluoranthene, benz[a]anthracene, benzo[a]pyrene, and benzo[ghi]perylene) in a solution using GC/MS-based methods. The PAHs measured in CCQM-K38 were selected to be representative of PAHs typically used as calibrants in the determination of the PAHs found in environmental samples and to provide the typical analytical measurement challenges encountered in the value-assignment of these PAH calibration solutions, such as volatility losses and resolution from potential interferences and other PAHs present as components in the solution during chromatographic separation. The abilities demonstrated by the laboratories that provided comparable measurements for all five PAHs in this Key Comparison should be indicative of their ability to provide reference measurements for a suite of PAHs in solutions when present at levels greater than 3 µg/g provided the laboratory demonstrates an acceptable degree of separation of the PAHs in the specific solution being analyzed.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Quantification of 13 priority polycyclic aromatic hydrocarbons in human urine by headspace solid-phase microextraction gas chromatography–isotope dilution mass spectrometry

Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants in both living and working environments. The aim of this study was the development of a headspace solid-phase microextraction gas chromatography–isotope dilution mass spectrometry (HS-SPME/GC–IDMS) method for the simultaneous quantification of 13 PAHs in urine samples. Different parameters affecting PAHs extraction by HS-SPME were considered and optimized: type/thickness of fiber coatings, extraction temperature/time, desorption temperature/time, ionic strength and sample agitation. The stability of spiked PAHs solutions and of real urine samples stored up to 90 days in containers of different materials was evaluated. In the optimized method, analytes were absorbed for 60 min at 80 °C in the sample headspace with a 100 μm polydimethylsiloxane fiber. The method is very specific, with linear range from the limit of quantification to 8.67 × 10 3 ng L −1, a within-run precision of <20% and a between-run precision of <20% for 2-, 3- and 4-ring compounds and of <30% for 5-ring compounds, trueness within 20% of the spiked concentration, and limit of quantification in the 2.28–2.28 × 10 1 ng L −1 range. An application of the proposed method using 15 urine samples from subjects exposed to PAHs at different environmental levels is shown.

On the preferential solvation of drugs and PAHs in binary solvent mixtures

The preferential solvation parameters, i.e., the differences between the local and bulk mole fractions of the solvents in solutions of certain drugs and polycyclic aromatic hydrocarbons (PAHs) are derived from their solubilities in binary solvent mixtures by means of the inverse Kirkwood-Buff integral (IKBI) and the quasi-lattice quasi-chemical (QLQC) methods. The solutes include caffeine, niflumic acid, diazepam, benzocaine, phenacetin, paracetamol, nalidixic acid, anthracene, and tr-stilbene and both aqueous and non-aqueous mixtures are considered. The findings are rationalized in terms of the interactions between the solute and solvents and the solvent components among themselves.

Phytotoxicities of fluoranthene and phenanthrene deposited on needle surfaces of the evergreen conifer, Japanese red pine ( Pinus densiflora Sieb. et Zucc.)

Polycyclic aromatic hydrocarbons (PAHs) have been widely studied with respect to their carcinogenic and mutagenic effects on animals and human cells. Phenanthrene (PHE) and fluoranthene (FLU) effects on the needle photosynthetic traits of 2-year-old Japanese red pine ( Pinus densiflora Sieb. et. Zucc.) seedlings were investigated. Three months after fumigation of foliage with solutions containing these PAHs (10 μM each), FLU had negative effects on net photosynthesis at near-saturating irradiance, stomatal conductance, initial chlorophyll fluorescence, and the contents of total chlorophyll, magnesium, and ribulose 1,5-bisphosphate carboxylase (rubisco) of current-year needles. PHE had similar negative effects to FLU but in lesser magnitude. The effects of the PAHs were mitigated by the addition of an OH-radical scavenger (mannitol) into the PAH solutions. PAHs deposited on the surface of pine needles may induce the generation of reactive oxygen species in the photosynthetic apparatus, a manner closely resembling the action of the herbicide paraquat.

Determination of polycyclic aromatic hydrocarbons in vegetable oils using solid-phase microextraction–comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry

A simple and fast solid-phase microextraction method coupled with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry was developed for analysis of polycyclic aromatic hydrocarbons in edible oil, performed directly in a hexane solution of the oil. Sampling conditions (solvent used, extraction time, extraction temperature and fiber rinsing time) were optimized by using a sample of oil fortified with a standard solution of polycyclic aromatic hydrocarbons. The method was validated by calculating linear range, correlation coefficient, accuracy, repeatability, detection limit and quantification limit. The method was applied to several oils collected from the market and directly from an olive pomace extraction plant.

Solid-phase extraction with C 30 bonded silica for analysis of polycyclic aromatic hydrocarbons in airborne particulate matters by gas chromatography–mass spectrometry

A solid-phase extraction (SPE) method using triacontyl bonded silica (C 30) as sorbent was developed for the determination of 16 US Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matters quantitatively by gas chromatography–mass spectrometry (GC–MS). Optimization experiments were conducted using spiked standard aqueous solution of PAHs and real airborne particulates samples aiming to obtain highest SPE recoveries and extraction efficiency. Factors were studied in SPE procedures including the concentration of organic modifier, flow rate of sample loading and elution solvents. The ultrasonication time and solvents were also investigated. Recoveries were in the range of 68–107% for standard PAHs aqueous solution and 61–116% for real spiked sample. Limits of detection (LODs) and limits of quantification (LOQs) with standard solution were in the range of 0.0070–0.21 μg L −1 and 0.022–0.67 μg L −1, respectively. The optimized method was successfully applied to the determination of 16 PAHs in real airborne particulate matters.

Prediction of polycyclic aromatic hydrocarbon solubilities in benzene

AbstractSolubilities of polycyclic aromatic hydrocarbon (PAH) solutes; naphthalene, fluorene, acenaphthene, fluoranthene, anthracene, phenanthrene, pyrene, chrysene and triphenylene in benzene are predicted using UNIFAC, modified UNIFAC (Dortmund), and combination of Flory‐Huggins and Scatchard‐Hildebrand (FH‐SH) methods. Applicability of the R‐UNIFAC method to the binary PAHs in benzene systems is studied. Exponent R of the R‐UNIFAC method is used in the modified UNIFAC (Dortmund) model to get a new expression for combinatorial activity coefficient. It is shown that the group contribution models using exponent R in combinatorial part of the equation perform much better than the original ones but none of the models considered satisfactorily predicts solid‐liquid equilibria (SLE) of all PAHs studied (FH‐SH model gives a prediction error of 98.08% for chrysene + benzene system). It is also shown that accounting the heat capacity change on melting terms makes considerable difference with ideal solubility in the case of higher melting PAHs in benzene. Copyright © 2007 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Removal of naphthalene in Brij 30-containing solution by ozonation using rotating packed bed

The removal efficiency of polycyclic aromatic hydrocarbons (PAHs) by ozonation using a rotating packed bed (RPB) in the surfactant-containing solution is studied. As an ozonation process starts, the ozone-containing gas is introduced and transferred into to the solution. The target PAHs in the solution would be then eliminated via both the gas stripping and ozonation decomposition. The RPB, which provides high gravitational force by adjusting the rotational speed, is employed as a novel ozone contactor. The naphthalene (NAP) and Brij 30 are chosen as the model pollutant and surfactant. Note that the experiments with different concentrations of NAP, Brij 30, and inlet gas ozone are performed for the further investigation. The residual NAP, effluent dissolved oxygen and ozone, and off-gas ozone concentrations are simultaneously monitored. As a result, the removal of NAP in the RPB is remarkably efficient compared with the convectional contactors because of its greater mass transfer coefficient. Moreover, the removal efficiency of NAP is found significantly dependent on the concentrations of NAP, Brij 30, and inlet gas ozone. It takes about several minutes to reach the steady state under the conditions of this study. In addition, it suggests employing RPBs as ozone contacting devices for the high removal efficiency of NAP. Consequently, the present study is useful for the practicable understanding of application of RPBs for the ozonation of PAHs in surfactant-containing solution.

Flow-through system for the generation of standard aqueous solution of polycyclic aromatic hydrocarbons

Standard aqueous solution of organic pollutants is used for the development of analysis methods and novel water sampling devices. The use of solid-phase microextraction (SPME) and other novel technologies for research in water sampling and analysis requires systems for the reliable generation of standard aqueous solution. In this communication, a new flow-through system based on permeation is introduced for the generation of standard aqueous solution of polycyclic aromatic hydrocarbons (PAHs). The main difference between the new developed system and typical system is that the syringe pump was changed with a permeation generator. The generator-based permeation offers many advantages, including convenient, inexpensive, solvent-free, long lifetime and production of high concentrations of the target analytes. The observed change in the concentration of the six PAH compounds was less than 20% over 3 months.

Removal of sorbed polycyclic aromatic hydrocarbons from soil, sludge and sediment samples using the Fenton’s reagent process

The use of the Fenton’s reagent process has been investigated for the remediation of environmental matrices contaminated by polycyclic aromatic hydrocarbons (PAHs). Laboratory experiments were first conducted in aqueous solutions, to study the kinetics of oxidation and adsorption of PAHs. Benzo[ a]pyrene was more rapidly degraded than adsorbed, while only partial oxidation of fluoranthene occurred. In the case of benzo[ b]fluoranthene, its adsorption prevented its oxidation. Besides competition effects between PAHs were found, with slower oxidation of mixtures as compared to single PAH solutions. Apparition of some by-products was observed, and a di-hydroxylated derivative of benzo[ a]pyrene could be identified under our conditions. Consequently, application to solid environmental matrices (soil, sludge and sediment samples) was performed using large amounts of reagents. The efficiency of the Fenton treatment was dependent on the matrix characteristics (such as its organic carbon content) and the PAH availability (correlated to the date and level of contamination). However, no pH adjustment was required, as well as no iron addition due to the presence of iron oxides in the solid matrices, suggesting the potential application of Fenton-like treatment for the remediation of PAH-contaminated environmental solids.

Polymer film sensor for sampling and remote analysis of polycyclic aromatic hydrocarbons in clear and turbid aqueous environments

A sensor for remote analysis of polycyclic aromatic hydrocarbons (PAHs) has been developed. It is based on direct solid phase extraction of the pollutants on a polymeric film, followed by monitoring the laser induced fluorescence, emitted from the film, via optical fibers. The proposed sensor has been applied to direct PAH analysis in clear and turbid aqueous environments. Linear calibration plots have been obtained for PAH solutions containing both humic substances and clay suspensions. Detection limits in the range of 10 ppt have been achieved. Results are obtained almost instantaneously (in drinking water) or within minutes, in more complicated matrices. This set-up has provided considerable improvement of the detection limits, when compared to the traditional fiber-optic fluorescence probe. In case of pyrene, a 100-fold and a 250-fold improvement in the detection limits have been obtained for the clay and humic substances-containing water, respectively. The spectral response of the polymeric film has been studied under various conditions and the feasibility of the method for analysis of PAH mixtures has been addressed.

Remediation of Matrices Contaminated by Polycyclic Aromatic Hydrocarbons: Use of Fenton's Reagent

The presence of toxic organic micropollutants in municipal sewage sludges is a major problem on account of risks associated with the agricultural valorization of the sludges. Therefore, a process that would enable reduction in organic pollutant concentrations in sewage sludges would be of great interest. The aim of this study was to investigate the use of the Fenton's reagent (Fe(II)-H 2 O 2 ) to degrade polycyclic aromatic hydrocarbons (PAHs) in sewage sludges. As the Fenton's reagent generates hydroxyl radicals that further oxidize pollutants in the solution, the authors' efforts focused on finding experimental conditions that would ensure stability of aqueous PAH solutions, and also allow the Fenton's reaction to occur in the medium. It appeared that Teflon recipients along with the addition of an organic solvent or the use of surfactants were required for obtaining stable PAHs solutions. However, a nonionic surfactant (Brij-35) was more suitable as it minimizes hydroxyl radical consumption.

Photochemical treatment of a mixed PAH/surfactant solution for surfactant recovery and reuse

AbstractBecause of their hydrophobic nature, polycyclic aromatic hydrocarbons (PAHs) are generally thought to be unavailable to in situ remediation processes, and solubilization of PAHs by surfactants is usually recommended. However, mixed PAH/surfactant solutions are wastewaters that need a post‐treatment after solubilization. In this study, mixed solutions of PAH and perfluorinated surfactant (PFS) were photochemically treated with and without hydrogen peroxide (H2O2), and the subsequent recovery and reuse of surfactant solutions were demonstrated. Phenanthrene and pyrene were selected as representative PAHs and lithium perfluorooctanesulfonate (LiFOS) as a PFS. Direct photolysis (UV only) and UV/H2O2 process enhanced the PAH degradation in LiFOS solutions compared to water. Both treatment processes selectively degraded PAHs without damaging PFS, suggesting that PFS withstands photolysis. Overall, it is demonstrated that UV and UV/H2O2 processes of mixed PAH/PFS solutions are effective for surfactant recovery/reuse, as well as PAH degradation.

Partition controlled delivery of hydrophobic substances in toxicity tests using poly(dimethylsiloxane) (PDMS) films.

Interpretation of toxicity test results may be hampered when doubt exists about the actual exposure concentration. Processes that are responsible for differences between the nominal and the actual concentration in aqueous test systems may include sorption, precipitation, volatilization, chemical and biological degradation, and uptake into biological or test tissue. In this study, the use of a poly(dimethylsiloxane) (PDMS) film containing the test compound is introduced as a versatile technique for partition controlled delivery of hydrophobic compounds to aqueous toxicity tests. Two methods developed produced preloaded films, having toxicant added to the PDMS prepolymer solution before film deposition and curing, and postloaded films, which are created by the addition of toxicant in a solvent to an already-polymerized PDMS film. Preloaded films were generally more easily prepared, may better accommodate larger molecules, and have a higher capacity than postloaded films. Postloaded films provided film-solution partition coefficients with higher precision and allowed for the use of films from stock and thus for a more portable technique. Chemical analysis showed that equilibrium between films and the aqueous solution was established within 7-10 min and was maintained for a suite of aromatic compounds (log Kow ranging from 2.8 to 6.1). The reliability of the film technique was demonstrated by application to the Microtox bacterial toxicity tests of solutions of polycyclic aromatic hydrocarbons (PAHs).

Aqueous sonolytic decomposition of polycyclic aromatic hydrocarbons in the presence of additional dissolved species

Sonochemical degradation of aqueous polycyclic aromatic hydrocarbons (PAHs) results in a first-order loss of the PAHs ( k=0.010–0.027 s −1 ). When sonication occurred in the presence of other organic compounds, the degradation rate constant was reduced quite dramatically. This reduction is believed to come about through scavenging of radicals by the matrix chemical. When oxygen was bubbled into the PAH solution before sonication, the degradation rate constant was elevated. Nitrogen purging resulted in decreased rate constants. These results indicate that oxygen was an important precursor in the degradation of the PAHs. Organic compounds, including humic acid, benzoic acid, and sodium dodecyl sulfate, decreased PAH degradation rate constants by scavenging oxygen derived reactive transients.

Laterally attached liquid crystalline polymers as stationary phases in reversed-phase high-performance liquid chromatography: V. Study of retention mechanism using linear solvation energy relationships

A linear solvation energy relationship model was used to characterize the retention behavior of a stationary phase based upon a nematic side-on liquid crystalline polymer (SOLCP) in reversed-phase liquid chromatography. The set of solutes was constituted of a high variety of compounds whose molecular sizes were considerably smaller than the mesogenic unit size. The results showed good statistical fits for these retention data in 65:35, 75:25 and 85:15 (v/v) methanol–water mobile phases. Both the cavity term and excess molar refraction are the most important favorable retention-governing parameters, whereas the solute hydrogen bond acceptor basicity is the most unfavorable retention parameter. Hydrophobicity and π–π interactions decrease strongly when the percentage of methanol increases, leading to an important retention decrease despite the fact that the hydrogen bond interaction weakens as the organic solvent is added. The shape recognition ability of this side-on liquid crystalline stationary phase on polycyclic aromatic hydrocarbon solutes is partly explained by the solutes’ high polarizability due to the presence of π-electrons. However, the solute polarizability is not sufficient and a stationary phase’s “structure effect” must to be taken into account for the shape discrimination observed. The strong interaction between liquid crystal molecules caused likely a adsorption retention mechanism rather than a partition mechanism.

Fenton Oxidation of Polycyclic Aromatic Hydrocarbons After Surfactant-Enhanced Soil Washing

The feasibility of using a combination of two well-studied technologies - soil washing and Fenton oxidation - to remove polycyclic aromatic hydrocarbons (PAH) from soil and subsequently destroy them in the resulting waste water solution was investigated. Three well-characterized New Jersey soils, representing a wide range of organic carbon content, were artificially contaminated with a mixture of anthracene, phenanthrene, and fluoranthene to simulate PAH-contaminated field soil. Batch laboratory-scale surfactant-enhanced soil washing was used to remove PAH from these soils. Two nonionic octylphenyl ethoxylate-type surfactants - Triton X-100 and Igepal CA-720 - were employed. PAH concentration in wash solution containing 1% surfactant was increased by over an order of magnitude above the level possible with water alone. The resulting solutions were treated with Fenton's reagent (H2O2 plus Fe2+) to destroy PAH in solution. Greater than 99% of PAH parent material was destroyed in the Triton X-100 wash soluti...