Solid-phase extraction and purification for the quantification of polycyclic aromatic hydrocarbon metabolites in fish bile

An analytical protocol including solid-phase extraction and purification is described for the individual quantification of polycyclic aromatic hydrocarbon metabolites (hydroxylated PAHs) in liquid biological matrices such as plasma and bile. The method consists in an enzymatic deconjugation followed by a solid-phase extraction on a C₁₈ cartridge and by a cleanup on an NH₂ cartridge. Extracts are then submitted to a derivatization step before gas chromatography/mass spectrometry (GC/MS) analysis. The quantification of PAH metabolites is ensured by adding an internal standard, 1-hydroxypyrene deuterated, at the beginning of the protocol. Recoveries obtained for the entire protocol were for the major part of the compounds between 96 and 70%. However, recoveries were not so satisfying concerning 2-hydroxybiphenyl and especially 3-hydroxybenzo(a)pyrene, with 62 and 36% respectively. Finally, the protocol was applied to different fish bile samples and showed its good applicability to fish bile samples. The NH₂ cleanup step has been proved to be a very selective purification step, necessary to remove most of the bile pigments before GC/MS injection. Different PAH metabolites could be detected in those natural samples and their quantification allowed us to distinguish different levels of fish exposure.     

Particle-size distribution of polycyclic aromatic hydrocarbons in urban air in southern Spain

The size distribution of polycyclic aromatic hydrocarbons (PAH) was determined for airborne particles from a large city with high vehicular traffic. The analytical method was optimised and validated using NIST standard reference material (SRM 1649a Urban Dust). The 16 priority PAH listed in the US-EPA were Soxhlet-extracted from filtered particulate matter and then fractionated using on-column chromatography. The aromatic fraction was quantified by gas chromatography-mass spectrometry. Real samples of particles collected in Seville (Spain) were analysed using the validated method. Values for the total concentration of PAH in the air, as well as the concentrations of each PAH in six particle-size ranges were obtained. Values of the PAH in TSP, PM₁₀, PM_2.5 and PM₁ were assessed.     

Monitoring of Polychlorinated Biphenyls in Surface Water Using Liquid Extraction,GC/MS,and GC/ECD

Abstract

A rapid and reliable analytical method, at trace level concentration was developed and validated for monitoring polychlorinated biphenyls (PCBs) in Jordanian surface water. The method combines the advantage of liquid extraction together with gas chromatography‐mass spectrometry (GC/MS) and gas chromatography‐electron capture detector (GC/ECD). The performance of the method was evaluated by analyzing certified reference material (CRM) of the analytes and applied on real water samples collected from different sites in Jordan. A mixture of 60∶40 dichloromethan‐petroleum ether was chosen as a convenient binary solvent for liquid–liquid extraction. The GC conditions for GC/MS were optimized using He as a carrier gas, temperature programming, and chlorpropham as an internal standard (IS).

The conditions for GC/ECD were performed using N₂ gas and a temperature program from 160 to 280°C with different increasing rates. The method of GC/MS in the selective ion mode (SIM) gave linear relationships for all PCBs tested between 0.60–6.0 µg/l with R ²=0.9934 (n=7×18). Recoveries from spiked water samples ranged between 87.6 and 91.4%. The mean accuracy and precision obtained were 4.9% and 2.16%, respectively. The mean of detection limit was 0.14±0.04 µg/l. In GC/ECD, linear relationships for all PCBs examined over the range of 0.3–2.4 µg/l was verified as characterized by a linear regression equation and correlation coefficient, R ²=0.9915 (n=12). The average precision and accuracy were 4.86% and 5.21%, respectively. Analyses results clarified that none of the examined Jordanian water samples contained any of the searched for PCBs within the detection limit achieved.     

Comparison of microprobe two-step laser desorption/laser ionization mass spectrometry and gas chromatography/ mass spectrometry studies of polycyclic aromatic hydrocarbons in ancient terrestrial rocks

Microprobe two-step laser desorption/laser ionization mass spectrometry (μL²MS) and gas chromatography/mass spectrometry (GC/MS) were used to analyze polycyclic aromatic hydrocarbons (PAHs) in ancient terrestrial rocks. μL²MS provides an in situ analysis of very small samples, records the PAHs with no isomer information, and gives quantitative data on the degree of alkylation of a given PAH series over the complete mass range. GC/MS provides isomer separation and quantitation of PAHs in bitumen but not kerogen, and is limited by sample size. Combination of these techniques allows analysis of very small samples by μL²MS with GC/MS confirmation of isomer distributions of the solvent extractable components (bitumen). It was found that the concentration of bitumen within the rock samples affects the PAH alkylation signal for μL²MS. At low bitumen concentrations μL²MS can produce pyrolysis products from kerogen that is present; however, as bitumen concentrations increase, the PAH distribution from bitumen dominates the signal.     

Quantitative analysis of polycyclic aromatic hydrocarbons using high-performance liquid chromatography-photodiode array-high-resolution mass spectrometric detection platform coupled to electrospray and atmospheric pressure photoionization sources

Polycyclic aromatic hydrocarbons (PAHs) are common pollutants present in atmospheric aerosols and other environmental mixtures. They are of particular air quality and human health concerns as many of them are carcinogenic toxins. They also affect absorption of solar radiation by aerosols, therefore contributing to the radiative forcing of climate. For environmental chemistry studies, it is advantageous to quantify PAH components using the same analytical technics that are commonly applied to characterize a broad range of polar analytes present in the same environmental mixtures. Liquid chromatography coupled with photodiode array and high-resolution mass spectrometric detection (LC-PDA-HRMS) is a method of choice for comprehensive characterization of chemical composition and quantification of light absorption properties of individual organic compounds present in the environmental samples. However, quantification of non-polar PAHs by this method is poorly established because of their imperfect ionization in electrospray ionization (ESI) technique. This tutorial article provides a comprehensive evaluation of the quantitative analysis of 16 priority pollutant PAHs in a standard reference material using the LC–MS platform coupled with the ESI source. Results are further corroborated by the quantitation experiments using an atmospheric pressure photoionization (APPI) method, which is more sensitive for the PAH detection. The basic concepts and step-by-step practical guidance for the PAHs quantitative characterization are offered based on the systematic experiments, which include (1) Evaluation effects of different acidification levels by formic acid on the (+)ESI-MS detection of PAHs. (2) Comparison of detection limits in ESI+ versus APPI+ experiments. (3) Investigation of the PAH fragmentation patterns in MS² experiments at different collision energies. (4) Calculation of wavelength dependent mass absorption coefficient (MAC_λ) of the standard mixture and its individual PAHs using LC-PDA data. (5) Assessment of the minimal injected mass required for accurate quantification of MAC_λ of the standard mixture and of a multi-component environmental sample.     

Simultaneous analysis of carbohydrates,polyols and amines in urine samples using chemical ionization gas chromatography with tandem mass spectrometry

A simple method for the simultaneous derivatization of carbohydrates, polyols, amines and amino acids using hexamethyldisilazane and N,O‐bis(trimethylsilyl)trifluoroacetamide was developed. This method allows the direct derivatization of urine samples without sample pretreatment before derivatization. The method was successfully used for analysis of the selected metabolites in urine samples of healthy individuals and neonates suffering from galactosemia. The limits of detection by positive chemical ionization gas chromatography with tandem mass spectrometry analysis were in the range of 1.0 mgL^‐1 for mannitol to 4.7 mg/L for glucose.     

Comparison of different methods to estimate the uncertainty in composition measurement by chromatography

Natural gas is a mixture that contains hydrocarbons and other compounds, such as CO₂ and N₂. Natural gas composition is commonly measured by gas chromatography, and this measurement is important for the calculation of some thermodynamic properties that determine its commercial value. The estimation of uncertainty in chromatographic measurement is essential for an adequate presentation of the results and a necessary tool for supporting decision making. Various approaches have been proposed for the uncertainty estimation in chromatographic measurement. The present work is an evaluation of three approaches of uncertainty estimation, where two of them (guide to the expression of uncertainty in measurement method and prediction method) were compared with the Monte Carlo method, which has a wider scope of application. The aforementioned methods for uncertainty estimation were applied to gas chromatography assays of three different samples of natural gas. The results indicated that the prediction method and the guide to the expression of uncertainty in measurement method (in the simple version used) are not adequate to calculate the uncertainty in chromatography measurement, because uncertainty estimations obtained by those approaches are in general lower than those given by the Monte Carlo method.     

Determination of column selectivity toward polycyclic aromatic hydrocarbons

An empirical test is described for the evaluation of column selectivity in reversed-phase liquid chromatography. Using a test mixture of three polycyclic aromatic hydrocarbons (PAH), overall column selectivity toward PAH was assessed for over 20 different commercial C₁₈ columns. Retention behavior was correlated to phase type (i.e., monomeric and polymeric surface modification chemistry) for custom synthesized phases. A classification scheme is proposed in which commercial C₁₈ columns are grouped into three classes based on retention behavior: monomeric-like, polymeric-like, and intermediate phase selectivity toward PAH. Correlation of retention behavior of the test mixture with the separation of PAH mixtures and with more general column properties (e.g., phase thickness) is discussed.     

Synthèse,séparation et identification par chromatographie gazeuse sur colonne capillaire d'hydrocarbures polycycliques aromatiques

Résumé L'hydrogénation de plusieurs hydrocarbures aromatiques polycycliques condensés (PAH) a été réalisée au moyen de RhCl₃·3H₂O et NaBH₄ en milieu éthanol-tétrahydrofuranne à 40°C et pression atmosphérique. On obtient ainsi rapidement la plupart des divers composés partiellement hydrogénés prévisibles, séparés par chromatographie gazeuse sur colonne capillaire. Leur identification a été réalisée par chromatographie gazeuse couplée à la spectrométrie de masse, par résonance magnétique nucléaire¹H et par comparaison avec des étalons authentiques. Qualques nouveaux Index de rétention ont été déterminés et contribuent à l'identification des PAH semihydrogénés dans les produits d'hydroliquéfaction et de pyrolyse du charbon.

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Synthesis, separation and identification by glass capillary gas chromatography of partly-hydrogenated, polycyclic aromatic hydrocarbons

Summary Hydrogenation of several polycyclic aromatic hydrocarbons (PAH) has been achieved with RhCl₃·3H₂O and NaBH₄ in a ethanol-tetrahydrofuran mixture at 40°C and atmospheric pressure. This method, suitable for most PAH, quickly leads to the expected partly-hydrogenated compounds which have been separated by glass capillary gas chromatography. They were identified by GC-MS and proton NMR spectroscopy by comparison with authentic samples. Some new retention indices have also been determined and contribute to the identification of partly hydrogenated PAH in coal liquefaction and pyrolysis products.

     

Development of an impurity‐profiling method for source identification of spilled benzene series compounds by gas chromatography with mass spectrometry: Toluene as a case study

In this study, an impurity profiling method was established for the source identification of spilled benzene series compounds. Toluene was used as a case study to demonstrate the feasibility of this approach. Gas chromatography with mass spectrometry was applied for identification and quantification of the impurities including ethyl benzene, p‐xylene, m‐xylene, and o‐xylene in toluene. Impurities in toluene were detected at very low levels by applying mass spectrometry in selected‐ion monitoring mode. Eight authentic toluene samples collected from different manufacturers were analyzed by the developed gas chromatography with mass spectrometry method to construct the characteristic impurity profiling of toluene. Then, combined with scatter distribution, similarity analysis and t‐test, a suite of diagnostic ratios based on the impurity distribution was used for the differentiation of toluene from different sources. Results indicated that scatter distribution method can discriminate the original toluene samples from different manufacturers. Similarity calculation and t‐test methods can identify effectively the weathered toluene samples. The proposed impurity profiling method was useful for discrimination between toluene samples from different sources. Statistical analysis of these impurity profiles demonstrated the potential to investigate whether two questioned spilled toluene samples encountered in forensic casework are from the same source.     

Investigation of the role of the carrier gas in capillary gas-solid chromatography

Nonideal interactions of the sorbate and the carrier gas and adsorption of the sorbate on the adsorbent surface in capillary gas-solid chromatography were studied. Chromatographic retention was found to be largely determined by adsorption processes. With respect to the retention coefficients (capacity factors) of a sorbate (k) with different carrier gases (P₁ and P₂), the correlation relationshipk(P₂) =A·k(P₁) +B (A, B are parameters of the equation) is closely obeyed. The advantages of carbon dioxide as the carrier gas were analyzed; the use of carbon dioxide allows the efficiency of the column to be enhanced.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 627–633, March, 1996.     

Large Volume Injection in Fast Gas Chromatography with On‐Column Injector

In this work a fast gas chromatography set‐up with on‐column injection was optimized and evaluated with a model mixture of C₈–C₂₈ n‐alkanes. Usual injection volumes when using narrow‐bore (e. g., 0.1 mm i.d.) analytical columns are ca. 0.1 μL. The presented configuration allows introduction of 10–30‐fold larger sample volumes without any distortion of peak shapes. In the set‐up a normal‐bore retention gap (1 m×0.32 mm i. d.) was coupled to a narrow‐bore (4.8 m×0.1 mm i. d.×0.4 μm film thickness) analytical column using a low dead volume column connector. The effects of the experimental conditions such as inlet pressure, sample volume, initial injection temperature, and oven temperature on a peak focusing are discussed. H‐u curves for helium and hydrogen are used to compare their suitability for high speed gas chromatography and to show the dependence of separation efficiency on the carrier gas velocity at high inlet pressures. In the fast gas chromatography system a baseline separation of C₁₀–C₂₈ n‐alkanes was achieved in less than 3 minutes.     

Application of direct thermal desorption gas chromatography time-of-flight mass spectrometry for determination of nonpolar organics in low-volume samples from ambient particulate matter and personal samplers

Direct thermal desorption and in-situ derivatization thermal desorption methods in conjunction with gas chromatography time-of-flight mass spectrometry have been characterized and evaluated for analysis of trace components from filters loaded with ambient particulate matter (PM). The limits of quantification were in the range of 7–24 pg for n-alkanes, 20 pg for hopanes, and 4–22 pg for polycyclic aromatic hydrocarbons (PAH). The limit of quantification was defined as the minimum amount of substance that conforms to the minimum distinguishable signal plus 9 times the standard deviation of this background signal from PM-loaded filters. The method has been successfully applied to low-volume samples from ambient PM collected with stationary and personal samplers. Stationary samples were collected in winter 2008 and 2010 in Augsburg, Germany. Sample aliquots of 0.2-0.3 m3 from stationary sampling were analyzed. High diurnal variation in concentration and source contribution was found especially during periods with low wind speed and low mixing layer height. High contributions of solid fuel combustion (wood and coal) were found in evening and nighttime samples, leading to peak PAH concentrations at midnight more than 10 times higher than at noon. Finally, the method was applied to samples collected by means of a personal sampler, i.e. a micro aethalometer, in Xi’an, China. Quantitative data on n-alkanes, hopanes, and PAH were obtained from sample volumes of 17 and 24 l. The impact of different sources such as vehicular and biogenic emissions could be distinguished.     

Matrix solid‐phase dispersion with chitosan‐zinc oxide nanoparticles combined with flotation‐assisted dispersive liquid–liquid microextraction for the determination of 13 n‐alkanes in soil samples

In this study, chitosan‐zinc oxide nanoparticles were used as a sorbent of miniaturized matrix solid‐phase dispersion combined with flotation‐assisted dispersive liquid–liquid microextraction for the simultaneous determination of 13 n‐alkanes such as C₈H₁₈ and C₂₀H₄₂ in soil samples. The solid samples were directly blended with the chitosan nanoparticles in the solid‐phase dispersion method. The eluent of solid‐phase dispersion was applied as the dispersive solvent for the following flotation‐assisted dispersive liquid–liquid microextraction for further purification and enrichment of the target compounds prior to gas chromatography with flame ionization detection. Under the optimum conditions, good linearity with correlation coefficients in the range 0.9991 < r² < 0.9995 and low detection limits between 0.08 to 2.5 ng/g were achieved. The presented procedure combined the advantages of chitosan‐zinc oxide nanoparticles, solid‐phase dispersion and flotation‐assisted dispersive liquid–liquid microextraction, and could be applied for the determination of n‐alkanes in complicated soil samples with acceptable recoveries.     

Carbon and oxygen isotope microanalysis of carbonate

Technical modification of the conventional method for the δ¹³C and δ¹⁸O analysis of 10–30 µg carbonate samples is described. The CO₂ extraction is carried out in vacuum using 105% phosphoric acid at 95°C, and the isotopic composition of CO₂ is measured in a helium flow by gas chromatography/isotope ratio mass spectrometry (GC/IRMS). The feed‐motion of samples to the reaction vessel provides sequential dropping of only the samples (without the sample holder) into the acid, preventing the contamination of acid and allowing us to use the same acid to carry out very large numbers of analyses. The high accuracy and high reproducibility of the δ¹³C and δ¹⁸O analyses were demonstrated by measurements of international standards and comparison of results obtained by our method and by the conventional method. Our method allows us to analyze 10 µg of the carbonate with a standard deviation of ±0.05‰ for δ¹³C and δ¹⁸O. The method has been used successfully for the analyses of the oxygen and carbon isotopic composition of the planktonic and benthic foraminifera in detailed palaeotemperature reconstructions of the Okhotsk Sea. Copyright © 2009 John Wiley & Sons, Ltd.     

A convenient technique for determination of reactivity ratios

A new technique to determine the reactivity ratios for monomers is described. It is based on vapor-phase chromatography and can be used for any volatile monomer. A new simplified equation was deduced which permits the direct use of the retention times to obtain the pair r₁r₂. The method is suggested for use in determination of the molar ratios of the chemical units in the polymer chain, regardless of chemical composition or constitution. The simplicity of this technique allows its use for monomer–polymer systems composed of any number of volatile monomers. The validity of this method was checked by using the pair methyl methacrylate–styrene. This technique is also being applied to the study of kinetics in polymerizations, since it allows the measurements of several samples taken from a single experiment.     

Field Evaluation of N-Methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) Coated Silica Gel Cartridges for the Measurement of Lower Carbonyls in Air

A rapid analytical method based on Soxhlet extraction has been developed for determination of polycyclic aromatic hydrocarbons (PAH) in palm dates and tuna fish. The method is based on selected ion-storage gas chromatography–mass spectrometry. In the work discussed we were interested in the analysis of 16 polycyclic aromatic hydrocarbons (PAH) regarded by the EPA as priority pollutants. Soxhlet extraction of real, fortified, and blank samples, with hexane as solvent, was used to extract the analytes of interest. An excellent detection limit and good relative standard deviations (RSD) were obtained and analysis time was short. The linearity and sensitivity of the method for measurement of these analytes at trace levels are discussed.     

Nitroarene products from the gas-phase reactions of volatile polycyclic aromatic hydrocarbons with the OH radical and N2O5

The nitroarene products of the gas-phase reactions of acenaphthylene, acenaphthene, phenanthrene, and anthracene-d₁₀ with N₂O₅ and the OH radical (in the presence of NO_x) are reported. The calculated atmospheric lifetimes of these polycyclic aromatic hydrocarbons (PAH), as well as those of naphthalene, 1- and 2-methylnaphthalene, biphenyl, fluoranthene, pyrene, and acephenanthrylene, show that reaction with the OH radical is the dominant loss process for these PAH, with the exception of acenaphthylene, acenaphthene, and acephenanthrylene which contain an external cyclopenta-fused ring. For these latter PAH, reaction with the NO₃ radical, and for acenaphthylene and acephenanthrylene reaction with O₃, are also expected to be important atmospheric loss processes. The nitroarenes observed as products of the atmospherically-important gas-phase reactions of the PAH in environmental chamber studies are compared with the nitroarenes measured in ambient air samples collected in California. It is concluded that although nitroarenes are formed in low yields (?5%) from the OH radical-initiated reactions of the PAH, atmospheric formation of nitroarenes may contribute significantly to ambient nitroarene concentrations.     

Estimating the PDMS-Coated, SPME-Fibre/Water- and Fibre/Gas-Partition Coefficients of Chlorinated Ethenes by Headspace-SPME

In this work, a simple, fast and reproducible method is presented for the determination of fibre/liquid-phase and fibre/gas-phase partition coefficients of five chlorinated ethenes on a poly-(dimethylsiloxane), PDMS-coated, solid-phase microextraction fibre, by employing a headspace HS-SPME coupled with gas chromatography. The partition coefficients were estimated by a numerical method using a Level-I fugacity method coupled with parameter-estimation software. Dimensionless partition coefficients between SPME fibre and liquid as well as gas phases were obtained at temperatures of 10 °C, 25 °C and 30 °C. The partition coefficients of the fibre and the gas phase, K _fg, increase with decreasing temperature by a factor of ≈2 to 6, and they are directly proportional to the linear slope of the regression line. The same tendency is observed for the partition coefficient of the fibre and liquid phase, K _fw, in a factor ≈1.2 to 2.0. The sorption enthalpy is higher in the gas phase; therefore, the sorption onto the fibre is favoured at lower temperatures. The correlation of the log K _ow versus log K _fw and log K _oa versus log K _fg shows a linear relationship with the number of chlorine atoms in the C = C molecule. Long-term experiments resulted in sorption to Teflon surfaces and possible losses in 43 mL vials, not observed in 250 mL Boston bottles.     

Coupled N,C and S stable isotope measurements using a dual‐column gas chromatography system

Many laboratories routinely analyze plant, animal and soil samples with elemental analyzers coupled to isotope ratio mass spectrometers, obtaining rapid results for nitrogen (%N, δ¹⁵N) and carbon (%C, δ¹³C) from the same sample. The coupled N and C measurements are possible because of a gas chromatography (GC) separation of N₂ and CO₂ gases produced in elemental analysis. Adding a second GC column allows additional measurement of sulfur (%S, δ³⁴S) from the same sample, so that combined N, C and S information is obtained routinely. Samples are 1–15 mg, and replicates generally differ by less than 0.1‰ for δ¹⁵N, δ¹³C or δ³⁴S. An example application shows that the N, C, and S measurement system allows a three‐dimensional view of element dynamics in estuarine systems that are undergoing pollution inputs from upstream watersheds. Extension of these GC principles should allow coupled H, C, N, and S isotope measurements in future work. Copyright © 2007 John Wiley & Sons, Ltd.