Rate constants for the gas-phase reactions of a series of alkylnaphthalenes with the OH radical

Naphthalene and its C1- and C2-alkyl derivatives are semivolatile polycyclic aromatic hydrocarbons expected to be in the gas phase in ambient atmospheres and subject to degradation by gas-phase reactions with the hydroxyl (OH) radical. Using a relative rate method, rate constants for the gas-phase reactions of OH radicals with a series of alkylnaphthalenes have been measured at 298 +/- 2 K and at atmospheric pressure of air. The compounds studied include naphthalene, 1- and 2-methylnaphthalene (1-, 2-MN), 1- and 2-ethylnaphthalene (1-, 2-EN), and the 10 dimethylnaphthalene isomers (1,2-; 1,3-; 1,4-; 1,5-; 1,6-; 1,7-; 1,8-; 2,3-; 2,6-; and 2,7-DMN). Using 1,2,3-and 1,3,5-trimethylbenzene as reference compounds, the rate constant obtained for the OH radical reaction of naphthalene was (2.39 +/- 0.09) x 10(-11) cm3 molecule(-1) s(-1). Relative to naphthalene, the rate constants measured for the alkylnaphthalenes were (in units of 10(-11) cm3 molecule(-1) s(-1), where the errors given are two standard deviations and include the above uncertainty in the naphthalene rate constant) 1-MN, 4.09 +/- 0.20; 2-MN, 4.86 +/- 0.25; 1-EN, 3.64 +/- 0.41; 2-EN, 4.02 +/- 0.55; 1,2-DMN, 5.96 +/- 0.55; 1,3-DMN, 7.49 +/- 0.39; 1,4-DMN, 5.79 +/- 0.36; 1,5-DMN, 6.01 +/- 0.35; 1,6-DMN, 6.34 +/- 0.36; 1,7-DMN, 6.79 +/- 0.45; 1,8-DMN, 6.27 +/- 0.43; 2,3-DMN, 6.15 +/- 0.47; 2,6-DMN, 6.65 +/- 0.35; 2,7-DMN, 6.87 +/- 0.43. These data show that, under atmospheric conditions, the DMN isomers react most rapidly with the OH radical with calculated lifetimes of 1.9-2.4 h, followed by the MNs and ENs with lifetimes of 2.9-3.8 h and naphthalene with a lifetime of 5.8 h. These differences in reactivity were confirmed by the nighttime/daytime concentration ratios of the alkylnaphthalenes measured in ambient Riverside, CA, samples.     

Rate constants for the gas-phase reactions of a series of alkylnaphthalenes with the nitrate radical

Naphthalene and its methyl-, ethyl-, and dimethyl-derivatives are semivolatile polycyclic aromatic hydrocarbons expected to be in the gas phase in ambient atmospheres and are subject to nighttime degradation by gas-phase reactions with the nitrate (NO3) radical. Using a relative rate method, rate constants for the gas-phase reactions of NO3 radicals with a series of alkylnaphthalenes have been measured at 298 +/- 2 K and atmospheric pressure of air. The compounds studied were 1- and 2-methylnaphthalene (1- and 2-MN), 1- and 2-ethylnaphthalene (1- and 2-EN), and the 10 dimethylnaphthalene isomers (1,2-, 1,3-, 1,4-,1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6-, and 2,7-DMN). Sampling in Riverside, CA showed that these alkylnaphthalenes were readily detected in ambient air, with the exception of 1,8-DMN. The reactions of naphthalene and the alkylnaphthalenes with NO3 radicals proceed by initial addition of the radical to form an aromatic-NO3 adduct (with rate constant k(a)) which either decomposes back to reactants (with rate constant kb) or reacts with NO2 to form products (with rate constant k(c). Using naphthalene as the reference compound, the values of (k(a)k(c)/k(b)) obtained for the NO3 radical reactions (in units of 10(-28) cm(6) molecule(-2) S(-1), indicated errors are two least-squares standard deviations) were as follows: 1-MN, 7.15 +/- 0.37; 2-MN, 10.2 +/- 1.0; 1-EN, 9.82 +/- 0.69; 2-EN, 7.99 +/- 0.99; 1,2-DMN, 64.0 +/- 2.3; 1,3-DMN, 21.3 +/- 1.2; 1,4-DMN, 13.0 +/- 0.5; 1,5-DMN, 14.1 +/- 1.3; 1,6-DMN, 16.5 +/- 1.8; 1,7-DMN, 13.5 +/- 0.7; 1,8-DMN, 212 +/- 59; 2,3-DMN, 15.2 +/- 0.5; 2,6-DMN, 21.2 +/- 1.6; 2,7-DMN, 21.0 +/- 1.5.     

Reactions of chlorine atoms with a series of aromatic hydrocarbons

Aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), are present in urban and rural atmospheres. Reactions of PAHs with Cl atoms may occur in the marine boundary layer and in coastal regions. To assess the importance of these reactions and to investigate whether any unique chlorine-containing products are formed from these reactions, we have measured the rate constants for the gas-phase reactions of Cl atoms with toluene-d8, 1,3,5-trimethylbenzene (1,3,5-TMB), naphthalene, 1-methylnaphthalene-d10 (1-MN-d10), 1- and 2-methylnaphthalene (1- and 2-MN), 1- and 2-ethylnaphthalene (1- and 2-EN), and the dimethylnaphthalenes (DMNs) at 296 +/- 2 K. A relative rate technique was used, and, using our measured rate constant forthe reaction of Cl atoms with 1,3,5-TMB of 2.42 x 10(-10) cm3 molecule(-1) s(-1), the rate constants (in units of 10(-10) cm3 molecule(-1) s(-1)) are as follows: naphthalene, < or = 0.0091 +/- 0.0003; 1-MN, 1.21 +/- 0.16; 2-MN, 1.05 +/- 0.13; 1-EN, 2.12 +/- 0.35; 2-EN, 1.38 +/- 0.27; 1,2-DMN, 3.61 +/- 0.68; 1,3-DMN, 2.90 +/- 0.22; 1,4-DMN, 2.93 +/- 0.30; 1,5-DMN, 2.31 +/- 0.19; 1,6-DMN, 2.15 +/- 0.20; 1,7-DMN, 3.05 +/- 0.34; 1,8-DMN, 3.07 +/- 0.44; 2,3-DMN, 2.93 +/- 0.49; 2,6-DMN, 2.34 +/- 0.18; and 2,7-DMN, 2.00 +/- 0.22, where the indicated errors are two standard deviations and do not include the uncertainty in the rate constant for 1,3,5-TMB. The measured deuterium isotope effects for the toluene-d8 and 1-MN-d10 reactions indicate that the reactions proceed by initial H- (or D-) atom abstraction. The products identified and quantified from the toluene and 1-MN reactions using gas chromatography and in situ direct air sampling atmospheric pressure ionization tandem mass spectrometry were benzaldehyde (84% +/- 7% yield) and benzyl alcohol (11% +/- 2% yield) from toluene and 1-naphthaldehyde (approximately 36%, lower limit to yield) and 1-naphthyl alcohol (approximately 12%, lower limit to yield) from 1-MN. These products confirm that H-atom abstraction is the dominant, if not sole, reaction pathway for the alkylbenzenes and alkylnaphthalenes, consistent with the 100-fold lower rate constant measured for naphthalene compared to the alkylnaphthalenes and with the measured deuterium isotope effects.     

Enzymatic hydrolysis of edible Passiflora fruit glycosides

The combined action of Hemicellulase REG 2 and sweet almond glucosidase containing β-d-glucopyranosidase, α-l-rhamnopyranosidase, α-l-arabinopyranosidase and α-l-arabinfuranosidase activities allowed release of most of the volatile compounds bound as aglycones in edible Passiflora fruits. Great variability between the four species studied, P. edulis, P. edulis f falvicarpa, P. ligularis, P. molissima, was noticed. 2,5-Dimethyl-4-hydroxy-3-(2H) furanone (furaneol) was identified for the first time in bound form in purple and yellow passion fruit. Only geraniol was identified as the aglycone in P. molissima. and no terpenol is present in the hydrolysate obtained from P. ligularis. Several terpene diols: 2,6-dimethyl-1,8-octanediol, (E)- and (Z)-2,6-dimethylocta-2,7-diene-1,6-diol, 2,6-dimethylocta-3,7-dien-2,6-diol and 2,6-dimethylocta-1,7-dien-3,6-diol have been identified in both purple and yellow passion fruit and small amounts of (Z)-2,6-dimethylocta-2,7-diene-1,6-diol are present in P. molissima. α-Ionol derivatives oxygenated in position 3 seem to be characteristic of purple passion fruit whereas β-ionol compounds oxygenated in position 3 are the major norisoprenoids identified as the aglycone in yellow passion fruit. The bound norisoprenoid content of P. ligularis and P. molissima is low. Important concentrations of bound aromatic alcohols are found in purple and yellow passion fruit whereas phenolics can be considered as characteristic of purple varieties. ©     

Soil column evaluation of factors controlling biodegradation of DNT in the vadose zone

High concentrations of 2,4-dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) are present in vadose zone soils at many facilities where explosives manufacturing has taken place. Both DNT isomers can be biodegraded under aerobic conditions, but rates of intrinsic biodegradation observed in vadose zone soils are not appreciable. Studies presented herein demonstrate that nutrient limitations control the onset of rapid 2,4-DNT biodegradation in such soils. In column studies conducted at field capacity, high levels of 2,4-DNT biodegradation were rapidly stimulated by the addition of a complete mineral medium but not by bicarbonate-buffered distilled deionized water or by phosphate-amended tap water. Biodegradation of 2,6-DNT was not observed under any conditions. Microcosm studies using a DNT-degrading culture from column effluent suggest that, after the onset of 2,4-DNT degradation, nitrite evolution will eventually control the extent of degradation achieved by two mechanisms. First, high levels of nitrite (40 mM) were found to strongly inhibit 2,4-DNT degradation. Second, nitrite production reduces the solution pH, and at pH levels below 6.0, 2,4-DNT degradation slows rapidly. Under conditions evaluated in laboratory-scale studies, 2,4-DNT biodegradation enhanced the rate of contaminant loss from the vadose zone by a factor of 10 when compared to the washout due to leaching.     

Anaerobic oxidation of crude oil hydrocarbons by the resident microorganisms of a contaminated anoxic aquifer

The biodegradation of two crude oils by microorganisms from an anoxic aquifer previously contaminated by natural gas condensate was examined under methanogenic and sulfate-reducing conditions. Artificially weathered Alaska North Slope crude oil greatly stimulated both methanogenesis and sulfate reduction. Gas chromatographic analysis revealed the entire n-alkane fraction of this oil (C13-C34) was consumed under both conditions. Naphthalene, 2-methylnaphthalene, and 2-ethylnaphthalene were also biodegraded but only in the presence of sulfate. Alba crude oil, which is naturally depleted in n-alkanes, resulted in a relatively modest stimulation of methanogenesis and sulfate reduction. Polycyclic aromatic hydrocarbon biodegradation was similar to that found for the Alaska North Slope crude oil, but a broader range of compounds was metabolized, including 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene in the presence of sulfate. These results indicate that n-alkanes are relatively labile, and their biodegradation in terrestrial environments is not necessarily limited by electron acceptor availability. Polycyclic aromatic hydrocarbons are relatively more recalcitrant, and the biodegradation of these substrates appeared to be sulfate-dependent and homologue-specific. This information should be useful for assessing the limits of in situ crude oil biodegradation in terrestrial environments and for making decisions regarding risk-based corrective actions.     

Cyclodextrin enhanced biodegradation of polycyclic aromatic hydrocarbons and phenols in contaminated soil slurries

This work aimed to evaluate the relative contribution of soil catabolic activity, contaminant bioaccessibility, and nutrient levels on the biodegradation of field-aged polycyclic aromatic hydrocarbons and phenolic compounds in three municipal gas plant site soils. Extents of biodegradation achieved, in 6 week-long soil slurry assays, under the following conditions were compared: (i) with inoculation of catabolically active PAH and phenol-degrading microorganisms, (ii) with and without hydroxypropyl-beta-cyclodextrin supplementation (HPCD; 100 g L(-1)), and finally (iii) with the provision of additional inorganic nutrients in combination with HPCD. Results indicated no significant (p < 0.05) differences between biodegradation endpoints attained in treatments inoculated with catabolically active microorganisms as compared with the uninoculated control. Amendments with HPCD significantly (p < 0.05) lowered biodegradation endpoints for most PAHs and phenolic compounds. Only in one soil did the combination of HPCD and nutrients consistently achieve better bioremediation endpoints with respect to the HPCD-only treatments. Thus, for most compounds, biodegradation was not limited by the catabolic activity of the indigenous microorganisms but rather by processes resulting in limited availability of contaminants to degraders. It is therefore suggested that the bioremediation of PAH and phenol impacted soils could be enhanced through HPCD amendments. In addition, the biodegradability of in situ and spiked (deuterated analogues) PAHs following 120 days aging of the soils suggested that this contact time was not sufficient to obtain similar partitions to that observed for field-aged contaminants; with the spiked compounds being significantly (p < 0.05) more available for biodegradation.     

Intra-aggregate mass transport-limited bioavailability of polycyclic aromatic hydrocarbons to Mycobacterium strain PC01

Biodegradation kinetics for three- and four-ring PAHs by Mycobacterium sp. strain PC01 were measured in whole and density-fractionated estuarine sediments and in a system without intra-aggregate mass transport limitations. The biokinetic data in the systems with and without intra-aggregate mass transport limitations were compared with abiotic PAH desorption kinetics. The results indicate that intra-aggregate mass transport limitations, and not the intrinsic bacterial PAH utilization capacity, were most important in controlling the rate of biodegradation of sediment-sorbed PAHs. Achievable extent of biodegradation could be predicted by the independently measured traction of desorbable PAHs in the fast-diffusion regime of a two-domain intra-aggregate mass transport model. A closed-form mathematical model was developed to describe sediment-pore water partitioning and rapid aqueous-phase diffusion of PAHs through the macropore and mesopore network of sediment aggregates, followed by first-order biodegradation of desorbed PAHs in the bulk aqueous domain. The model effectively predicted independent biodegradation kinetics of PAHs field-aged in two estuarine sediments. Despite low aqueous solubility of PAHs, macropore and mesopore diffusion may be an important mechanism controlling intra-aggregate mass transport and bioavailability of the most readily and extensively desorbed PAHs in sediments.     

Effect of a nonionic surfactant on biodegradation of slowly desorbing PAHs in contaminated soils

The influence of the nonionic surfactant Brij 35 on biodegradation of slowly desorbing polycyclic aromatic hydrocarbons (PAHs) was determined in contaminated soils. We employed a soil originated from a creosote-polluted site, and a manufactured gas plant soil that had been treated by bioremediation. The two soils differed in their total content in five indicator 3-, 4-, and 5-ring PAHs (2923 mg kg(-1) and 183 mg kg(-1) in the creosote-polluted and bioremediated soils, respectively) but had a similar content (140 mg kg(-1) vs 156 mg kg(-1)) of slowly desorbing PAHs. The PAHs present in the bioremediated soil were highly recalcitrant. The surfactant at a concentration above its critical micelle concentration enhanced the biodegradation of slowly desorbing PAHs in suspensions of both soils, but it was especially efficient with bioremediated soil, causing a 62% loss of the total PAH content. An inhibition of biodegradation was observed with the high-molecular-weight PAHs pyrene and benzo[a]pyrene in the untreated soil, possibly due to competition effects with other solubilized PAHs present at relatively high concentrations. We suggest that nonionic surfactants may improve bioremediation performance with soils that have previously undergone extensive bioremediation to enrich for a slowly desorbing profile.     

Effect of NO₂ concentration on dimethylnitronaphthalene yields and isomer distribution patterns from the gas-phase OH radical-initiated reactions of selected dimethylnaphthalenes

Dimethylnitronaphthalene (DMNN) formation yields from the reactions of 1,7- and 2,7- dimethylnaphthalene (DMN) with OH radicals were measured over the NO(2) concentration range 0.04-1.4 ppmv. The measured DMNN formation yields under conditions that the OH-DMN adducts reacted solely with NO(2) were 0.252 ± 0.094% for Σ1,7-DMNNs and 0.010 ± 0.005% for Σ2,7-DMNNs. 1,7-DM-5-NN was the major isomer formed, with a limiting high-NO(2) concentration yield of 0.212 ± 0.080% and with equal reactions of the adduct with NO(2) and O(2) occurring in air at 60 ± 39 ppbv of NO(2). The reactions of the OH-DMN adducts with NO(2) must therefore result in products other than DMNNs. Although the yields of the DMNNs are low, ≤0.3%, the DMNN (and ethylnitronaphthalene) profiles from chamber experiments match well with those observed in polluted urban areas under conditions where OH radical-initiated chemistry is dominant. Daytime OH radical and nighttime NO(3) radical reactions appear to account for the alkylnitronaphthalenes formed and their observed profiles under most urban atmospheric conditions, with profiles reflecting daytime OH chemistry modified by contributions from isomers formed by any NO(3) radical chemistry that had occurred. Since the formation yields and NO(2) dependencies for the formation of a number of alkylnitronaphthalenes have now been measured, the effect of NO(x) emissions control strategies on their atmospheric formation can be quantitatively assessed, and the decrease in formation of these genotoxic species may provide a previously unrecognized health benefit of NO(x) control.     

Automobile tires--a potential source of highly carcinogenic dibenzopyrenes to the environment

Eight tires were analyzed for 15 high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAH), using pressurized fluid extraction. The variability of the PAH concentrations determined between different tires was large; a factor of 22.6 between the lowest and the highest. The relative abundance of the analytes was quite similar regardless of tire. Almost all (92.3%) of the total extractable PAH content was attributed to five PAHs: benzo[ghi]perylene, coronene, indeno[1,2,3-cd]pyrene, benzo[e]pyrene, and benzo[a]pyrene. The difference in the measured PAH content between summer and winter tires varied substantially across manufacturers, making estimates of total vehicle fleet emissions very uncertain. However, when comparing different types of tires from the same manufacturer they had significantly (p = 0.05) different PAH content. Previously, there have been no data available for carcinogenic dibenzopyrene isomers in automobile tires. In this study, the four dibenzopyrene isomers dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene, and dibenzo[a,h]pyrene constituted <2% of the sum of the 15 analyzed HMW PAHs. These findings show that automobile tires may be a potential previously unknown source of carcinogenic dibenzopyrenes to the environment.     

Effect of activated carbon amendment on bacterial community structure and functions in a PAH impacted urban soil

We collected urban soil samples impacted by polycyclic aromatic hydrocarbons (PAHs) from a sorbent-based remediation field trial to address concerns about unwanted side-effects of 2% powdered (PAC) or granular (GAC) activated carbon amendment on soil microbiology and pollutant biodegradation. After three years, total microbial cell counts and respiration rates were highest in the GAC amended soil. The predominant bacterial community structure derived from denaturing gradient gel electrophoresis (DGGE) shifted more strongly with time than in response to AC amendment. DGGE band sequencing revealed the presence of taxa with closest affiliations either to known PAH degraders, e.g. Rhodococcus jostii RHA-1, or taxa known to harbor PAH degraders, e.g. Rhodococcus erythropolis, in all soils. Quantification by real-time polymerase chain reaction yielded similar dioxygenases gene copy numbers in unamended, PAC-, or GAC-amended soil. PAH availability assessments in batch tests showed the greatest difference of 75% with and without biocide addition for unamended soil, while the lowest PAH availability overall was measured in PAC-amended, live soil. We conclude that AC had no detrimental effects on soil microbiology, AC-amended soils retained the potential to biodegrade PAHs, but the removal of available pollutants by biodegradation was most notable in unamended soil.     

Effect of interface fertilization on biodegradation of polycyclic aromatic hydrocarbons present in nonaqueous-phase liquids

The main goal of this study was to use an oleophilic biostimulant (S-200) to target possible nutritional limitations for biodegradation of polycyclic aromatic hydrocarbons (PAHs) at the interface between nonaqueous-phase liquids (NAPLs) and the water phase. Biodegradation of PAHs present in fuel-containing NAPLs was slow and followed zero-order kinetics, indicating bioavailability restrictions. The biostimulant enhanced the biodegradation, producing logistic (S-shaped) kinetics and 10-fold increases in the rate of mineralization of phenanthrene, fluoranthene, and pyrene. Chemical analysis of residual fuel oil also evidenced an enhanced biodegradation of the alkyl-PAHs and n-alkanes. The enhancement was not the result of an increase in the rate of partitioning of PAHs into the aqueous phase, nor was it caused by the compensation of any nutritional deficiency in the medium. We suggest that biodegradation of PAH by bacteria attached to NAPLs can be limited by nutrient availability due to the simultaneous consumption of NAPL components, but this limitation can be overcome by interface fertilization.     

Optimization for biodegradation of 2,4,6-trinitrotoluene (TNT) by Pseudomonas putida

In this study, a strain of Pseudomonas putida KP-T202, isolated from the soil in a contaminated site, degraded 2,4,6-trinitrotoluene (TNT). In order to make this biodegradation process commercially feasible and reduce biodegradation time, optimal environmental factors are determined. At an initial concentration of 100 mg/l, TNT was totally degraded within 15 h under aerobic conditions. The optimal conditions for the biodegradation of TNT were found to be 30 degrees C, pH 7, 1% corn steep liquor (CSL), 0.025% NH,CI and 0.1% Tween 80; the reaction rate constant was 0.348 h(-1) These environmental conditions can be used to improve the efficiency of large-scale reactors for the treatment of TNT-contaminated wastewater and soil. In addition, the intermediates were identified as 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,4-dinitrotoluene and 2,6-dinitrotoluene.     

Polycyclic aromatic hydrocarbons contamination of traditionally grilled pork marketed in South Benin and health risk assessment for the Beninese consumer

ABSTRACT

Polycyclic aromatic hydrocarbons (PAHs) contamination was monitored in grilled pork sold in Beninese street restaurants, as well as in grilled pork from a well-controlled experiment replicating traditional grilling using Acacia auriculiformis wood as fuel. Fifteen PAHs were analysed using a high-performance liquid chromatography method coupled with fluorescence detection. To assess the risk for the consumer, the margins of exposure (MOEs) were calculated, as the ratio between benchmark PAHs levels and consumer intakes. A MOE below 10,000 indicates a concern for human health for carcinogenic compounds such as PAHs. Benzo(a)pyrene (BaP) levels up to 17.9 and 53.6 µg/kg were found in grilled pork sampled in restaurants and from the controlled experiment, respectively. When considering both median estimated daily intake and median PAHs contamination levels, MOEs calculated for Benzo(a)pyrene (BaP) alone, or for the sum of 2, 4 or 8 PAHs were above 10,000, meaning no risk in these cases. However, for the same PAHs contamination level, MOE for consumers having large amounts of grilled pork (97.5th percentile and maximum level of pork consumption) were well below 10,000. When considering the maximum level of PAHs contamination, MOEs ranged between 257 and 2,757 for the high and median levels of consumption, indicating a safety concern for these consumers. This study reveals that Beninese grilled pork consumers from South Benin can be exposed to high levels of PAHs, which might result in public health issues.     

Extending the Rayleigh equation to allow competing isotope fractionating pathways to improve quantification of biodegradation

The Rayleigh equation relates the change in isotope ratio of an element in a substrate to the extent of substrate consumption via a single kinetic isotopic fractionation factor (alpha). Substrate consumption is, however, commonly distributed over several metabolic pathways each potentially having a different alpha. Therefore, extended Rayleigh-type equations were derived to account for multiple competing degradation pathways. The value of alpha as expressed in the environment appears a function of the alpha values and rate constants of the various involved degradation pathways. Remarkably, the environmental or apparent alpha value changes and shows non-Rayleigh behavior over a large and relevant concentration interval if Monod kinetics applies and the half-saturation constants of the competing pathways differ. Derived equations were applied to previously published data and enabled (i) quantification of the share that two competing degradation pathways had on aerobic 1,2-dichloroethane (1,2-DCA) biodegradation in laboratory batch experiments and (ii) calculation of the extent of methyl tert-butyl ether (MTBE) biodegradation shared over aerobic and anaerobic degradation at a field site by means of an improved solution to two-dimensional (carbon and hydrogen) compound-specific isotope analysis (CSIA).     

Rapid determination of polycyclic aromatic hydrocarbons in natural tocopherols by high-performance liquid chromatography with fluorescence detection

A simple and rapid method has been developed and validated for the determination of seventeen polycyclic aromatic hydrocarbons (PAHs) in natural tocopherol products. Samples were dissolved in n-hexane, cleaned by an alumina column, and separated and determined by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection. The recoveries were greater than 77.9%, except for the lowest molecular weight PAHs (Na, 1-Me, 2-Me, AC, F) which were between 15.9% and 75.8%. The limits of quantification were less than 0.38 ng/g for the heavy PAHs and less than 1.50 ng/g for the light PAHs. Good repeatabilities were achieved with RSD less than 10.7% for all the objective compounds. This method has been applied to evaluating PAHs contents in various natural tocopherol products and controlling natural tocopherol product quality.