Determination of trace hydroxyl polycyclic aromatic hydrocarbons in urine using graphene oxide incorporated monolith solid‐phase extraction coupled with LC‐MS/MS

The biomonitoring of hydroxy polycyclic aromatic hydrocarbons in urine, as a direct way to access multiple exposures to polycyclic aromatic hydrocarbons, has raised great concerns due to their increasing hazardous health effects on humans. Solid‐phase extraction is an effective and useful technique to preconcentrate trace analytes from biological samples. Here, we report a novel solid‐phase extraction method using a graphene oxide incorporated monolithic syringe for the determination of six hydroxy polycyclic aromatic hydrocarbons in urine coupled with liquid chromatography‐tandem mass spectrometry. The effect of graphene oxide amount, washing solvent, eluting solvent, and its volume on the extraction performance were investigated. The fabricated monoliths gave higher adsorption efficiency and capacity than the neat polymer monolith and commercial C₁₈ sorbent. Under the optimum conditions, the developed method provided the detection limits (S/N = 3) of 0.02–0.1 ng/mL and the linear ranges of 0.1–1500 ng/mL for six analytes in urine sample. The recoveries at three spiked levels ranged from 77.5 to 97.1%. Besides, the intra column‐to‐column (n = 3) and inter batch‐to‐batch (n = 3) precisions were ≤ 9.8%. The developed method was successfully applied for the determination of hydroxy polycyclic aromatic hydrocarbons in urine samples of coke oven workers.     

Supercritical fluid extraction followed by supramolecular solvent microextraction as a fast and efficient preconcentration method for determination of polycyclic aromatic hydrocarbons in apple peels

In this work, reverse micelle‐based supramolecular solvent microextraction method coupled with supercritical fluid extraction and used for determining trace amounts of polycyclic aromatic hydrocarbons in apple peels. The extract was analyzed by high‐performance liquid chromatography equipped with a fluorescence detector. Coupling supramolecular solvent microextraction with supercritical fluid extraction method, resolve low preconcentration factor of supercritical fluid extraction method, improved limit of detection of polycyclic aromatic hydrocarbons and allow the use of supramolecular solvent microextraction in solid matrices. The effective parameters on the supramolecular solvent microextraction and supercritical fluid extraction efficiency were optimized using one variable at a time and face centered design methods, respectively. Under the optimum condition, the limits of detection and limits of quantifications were in the range of 0.34–1.27 and 1.03–3.82 µg/kg, respectively. Analysis of polycyclic aromatic hydrocarbons in apple peels showed that the supercritical fluid extraction/ supramolecular solvent microextraction method provide great potential for trace analysis of polycyclic aromatic hydrocarbons in fruit samples (RSDs < 7.7%).     

Investigating the robustness and extraction performance of a matrix‐compatible solid‐phase microextraction coating in human urine and its application to assess 2–6‐ring polycyclic aromatic hydrocarbons using GC–MS/MS

In this work, a polydimethylsiloxane/divinylbenzene fiber overcoated with a layer of polydimethylsiloxane was evaluated as analytical sampling tool for the first time in human urine. Urinary polycyclic aromatic hydrocarbons with 2–6 aromatic rings were considered as target compounds. The analyte uptake in kinetic and thermodynamic regime was evaluated and compared to the performances of polydimethylsiloxane/divinylbenzene and polydimethylsiloxane fibers. The assessment of the robustness and endurance of the overcoated fiber was carried out by direct immersion solid‐phase microextraction in undiluted urine performing up to 120 consecutive extractions. The overcoated fiber was then used to develop a fast and easy direct immersion solid‐phase microextraction with gas chromatography and triple quadrupole mass spectrometry protocol for the quantification of the target polycyclic aromatic hydrocarbons. The attained values of accuracy and precision were 75–114% and 2–19%, respectively, while the limits of quantification ranged between 0.05 and 1 ng/L. The proposed protocol was applied to the screening of urine samples collected from smoking and nonsmoking volunteers. The successful results obtained by using the overcoated fiber create not only new alternatives for polycyclic aromatic hydrocarbon exposure assessment but also new perspectives for the application of direct immersion solid‐phase microextraction to the analysis of bioclinical matrixes.     

An in‐needle solid‐phase microextraction device packed with etched steel wires for polycyclic aromatic hydrocarbons enrichment in water samples

A novel, low‐cost and effective in‐needle solid‐phase microextraction device was developed for the enrichment of trace polycyclic aromatic hydrocarbons in water samples. The in‐needle solid‐phase microextraction device could be easily assembled by inserting hydrofluoric acid‐etched wires, which were used as adsorbent, into a 22‐gauge needle tube within spring supporters. Compared with the commercial solid‐phase microextraction fiber, the developed device has higher efficiency for the extraction of polycyclic aromatic hydrocarbons with four to six rings from water samples using the optimized extraction conditions. With gas chromatography equipped with a flame ionization detector, the limits of detection for the polycyclic aromatic hydrocarbons with four to six rings ranged from 0.0020 to 0.0067 ng/mL. The relative standard deviations for one needle and needle‐to‐needle extractions were in the range of 5.2–9.9% (n = 5) and 3.4–12.3% (n = 5), respectively. The spiked recoveries of the polycyclic aromatic hydrocarbons in tap water samples ranged from 73.2 to 95.4%. This in‐needle solid‐phase microextraction device could be a good field sampler because of the low sample loss over a long storage time.     

Inorganic–organic hybrid coating material for the online in‐tube solid‐phase microextraction of monohydroxy polycyclic aromatic hydrocarbons in urine

An inorganic–organic hybrid nanocomposite (zinc oxide/polypyrrole) that represents a novel kind of coating for in‐tube solid‐phase microextraction is reported. The composite coating was prepared by a facile electrochemical polymerization strategy on the inner surface of a stainless‐steel tube. Based on the coated tube, a novel online in‐tube solid‐phase microextraction with liquid chromatography and mass spectrometry method was developed and applied for the extraction of three monohydroxy polycyclic aromatic hydrocarbons in human urine. The coating displayed good extraction ability toward monohydroxy polycyclic aromatic hydrocarbons. In addition, long lifespan, excellent stability, and good compression resistance were also obtained for the coating. The experimental conditions affecting the extraction were optimized systematically. Under the optimal conditions, the limits of detection and quantification were in the range of 0.039–0.050 and 0.130–0.167 ng/mL, respectively. Good linearity (0.2–100 ng/mL) was obtained with correlation coefficients larger than 0.9967. The repeatability, expressed as relative standard deviation, ranged between 2.5% and 9.4%. The method offered the advantage of process simplicity, rapidity, automation, and sensitivity in the analysis of human urinary monohydroxy polycyclic aromatic hydrocarbons in two different cities of Hubei province. An acceptable recovery of monohydroxy polycyclic aromatic hydrocarbons (64–122%) represented the additional attractive features of the method in real urine analysis.     

New micromethod combining miniaturized matrix solid-phase dispersion and in-tube in-valve solid-phase microextraction for estimating polycyclic aromatic hydrocarbons in bivalves

Miniaturized matrix solid-phase dispersion (MSPD) was developed for the extraction of common polycyclic aromatic hydrocarbons (PAHs) from bivalve samples (100mg, dry weight). Additional clean-up and analyte enrichment was accomplished by in-tube solid-phase microextraction (SPME). For this purpose the extracts collected after MSPD were diluted with water and injected into a capillary column coated with the extractive phase. This capillary column was connected to the analytical column by means of a switching valve. Separation and quantification of the PAHs were carried out using a monolithic LC column and fluorescence detection. Since the in-tube SPME device allowed the processing of large volumes of the extracts (2.0 mL) excellent sensitivity was achieved, thus making solvent evaporation operations unnecessary. The overall recoveries ranged from 10% to 28% for the studied compounds. The relative standard deviation (RSD) ranged from 2% to 10% for intra-day variation (n=3), and the limits of detection (LODs) were < or =0.6 ng/g (dry weight). The proposed procedure was very simple and rapid (total analysis time was approximately 20 min), and the consumption of organic solvents and extractive phases was drastically reduced. The reliability of the proposed MSPD/in-tube SPME method was tested by analysing several bivalves (mussels and tellins) as well as a standard reference material (SRM).     

石墨烯应用于样品前处理的研究进展

样品前处理技术在样品分析中发挥着越来越重要的作用,而对分析物的富集能力和对样品基体的净化程度主要取决于高效的样品前处理材料,所以发展高性能的样品前处理材料一直是该领域的前沿研究方向。近年来,各类先进材料已经被引入样品前处理领域,发展了多种高性能的萃取材料。由于独特的物理化学性质,石墨烯已在各个研究领域获得广泛关注,在样品前处理领域也发挥着重要作用。基于高的比表面积、大的π电子结构、优异的吸附性能、丰富的官能团和易于化学改性等优点,石墨烯和氧化石墨烯基萃取材料被成功应用于各种样品的前处理,对不同领域中多种类型分析物表现出优异的萃取性能。该论文总结和讨论了近3年来石墨烯材料(石墨烯、氧化石墨烯及其功能化材料)在柱固相萃取、分散固相萃取、磁性固相萃取、搅拌棒萃取、纤维固相微萃取和管内固相微萃取等方面的研究进展。基于多种萃取机理如π-π、静电、疏水、亲水、氢键等相互作用,石墨烯萃取材料能够高效萃取和选择性富集不同类别的目标分析物,如重金属离子、多环芳烃、塑化剂、雌激素、药物分子、农药残留、兽药残留等。基于新型石墨烯萃取材料的各种样品前处理技术与多种检测技术如色谱、质谱、原子吸收光谱等联用,广泛应用于环境监测、食品安全和生化分析等领域。最后,总结了石墨烯在样品前处理领域中存在的问题,并展望了未来的发展趋势。     

Extraction and enrichment of polycyclic aromatic hydrocarbons by ordered mesoporous carbon reinforced hollow fiber liquid‐phase microextraction

A novel microextraction method, ordered mesoporous carbon reinforced hollow fiber liquid‐phase microextraction coupled with high‐performance liquid chromatography and fluorescence detection, was developed for the determination of some organic pollutants in water samples. Four polycyclic aromatic hydrocarbons (fluorene, anthracene, fluoranthene, and pyrene) were selected to validate this new method. Main parameters that could influence the extraction efficiency such as extraction time, fiber length, stirring rate, the type of the extraction solvent, pH value, the concentration of ordered mesoporous carbon, and salt effect were optimized. Under the optimal extraction conditions, good linearity was observed in the range of 2–1000 ng/L, with the correlation coefficients of 0.9954–0.9986. The recoveries for the spiked samples were in the range of 88.96–100.17%. The limits of detection of the method were 0.4–4 ng/L. The relative standard deviations varied from 4.2–5.9%. The results demonstrated that the newly developed method was an efficient pretreatment and enrichment procedure for the determination of polycyclic aromatic hydrocarbons in environmental water samples.     

Optimization of multiwalled carbon nanotubes reinforced hollow‐fiber solid–liquid‐phase microextraction for the determination of polycyclic aromatic hydrocarbons in environmental water samples using experimental design

A novel design of hollow‐fiber liquid‐phase microextraction containing multiwalled carbon nanotubes as a solid sorbent, which is immobilized in the pore and lumen of hollow fiber by the sol–gel technique, was developed for the pre‐concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples. The proposed method utilized both solid‐ and liquid‐phase microextraction media. Parameters that affect the extraction of polycyclic aromatic hydrocarbons were optimized in two successive steps as follows. Firstly, a methodology based on a quarter factorial design was used to choose the significant variables. Then, these significant factors were optimized utilizing central composite design. Under the optimized condition (extraction time = 25 min, amount of multiwalled carbon nanotubes = 78 mg, sample volume = 8 mL, and desorption time = 5 min), the calibration curves showed high linearity (R ² = 0.99) in the range of 0.01–500 ng/mL and the limits of detection were in the range of 0.007–1.47 ng/mL. The obtained extraction recoveries for 10 ng/mL of polycyclic aromatic hydrocarbons standard solution were in the range of 85–92%. Replicating the experiment under these conditions five times gave relative standard deviations lower than 6%. Finally, the method was successfully applied for pre‐concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples.     

Optimization of solid‐phase microextraction using Taguchi design to quantify trace level polycyclic aromatic hydrocarbons in water

This article introduces a simple, rapid, and reliable solid‐phase microextraction (SPME) method coupled with GC‐MS for the quantitative determination of 16 polycyclic aromatic hydrocarbons in water. In this study, the Taguchi experimental design was used to optimize extraction conditions of polycyclic aromatic hydrocarbons using SPME method to obtain highly enriched analytes. Consequently, quantitative determination of polycyclic aromatic hydrocarbons in water was achieved by GC‐MS technique. The selected parameters affecting enrichment of polycyclic aromatic hydrocarbons were sample extraction time, stirring speed, temperature, ionic strength, and pH. The study revealed that optimal operating conditions were found to be 90‐min extraction time, 1400 rpm stirring speed, and 60°C sample temperature. The effect of ionic strength and pH were shown to be insignificant. Optimized conditions were also reevaluated by placing the 16 polycyclic aromatic hydrocarbons into several subgroups based on their molecular weight. The extraction efficiency of polycyclic aromatic hydrocarbons with low molecular weight was shown to be a function of only the extracting temperature. Satisfactory results were obtained for linearity (0.983–0.999), detection limits (2.67–18.02 ng/L), accuracy (71.2–99.3%), and precision (4.3–13.5%). The optimum conditions reported by other design approaches were evaluated and generalized optimum conditions were suggested.     

π-hole bonding: A new retention mechanism for the solid phase extraction of polycyclic aromatic hydrocarbons from the hexane extracts of soil samples

In this work, the perfluorobenzene-bonded silica sorbent was tested to adsorb polycyclic aromatic hydrocarbons in hexane. In the comparison experiments, the perfluorobenzene-bonded sorbent's performance was better than octadecyl silica sorbent and phenyl-bonded silica sorbents, which indicated that the π-hole···π bonds between perfluorobenzene and the polycyclic aromatic hydrocarbons were stronger than π···π interactions and hydrophobic interactions in hexane. Then the perfluorobenzene-bonded silica sorbent was applied to solid-phase extraction of 15 polycyclic aromatic hydrocarbons from the hexane extracts of soil samples directly without the solvent replacement, which simplified the soil pretreatment process. And the results showed that under the optimal conditions, the proposed method for the determination of polycyclic aromatic hydrocarbons in the environment soil presented good recoveries and stabilities for the 10 heavier polycyclic aromatic hydrocarbons with the recoveries ranging from 75.1% to 104.6% and the relative standard deviations being in the range of 1.4%–5.8%. The limits of detection of the method varied from 0.1 to 2 ng/g. This work reveals the great application potential of the π-hole bond as a new retention mechanism in the field of solid-phase extraction.     

Trace level determination of polycyclic aromatic hydrocarbons in river water with automated pretreatment HPLC

A novel on‐line pretreatment pump‐injection HPLC system for polycyclic aromatic hydrocarbons is proposed. We report novel pump‐injection HPLC‐based on‐line SPE with a specially designed pretreatment column for the determination of trace amounts of chemical substances in surface water. Polycyclic aromatic hydrocarbons are well known for strong carcinogenicity and thus a severe concentration control is required for drinking water and/or river water, which is the main resource of tap water. We found it possible to detect ng/L levels of polycyclic aromatic hydrocarbons by using pump‐injection column switching HPLC with fluorescence detection. To avoid the phenomenon, in which polycyclic aromatic hydrocarbons can be often adsorbed on the surface of flow lines of HPLC by their highly hydrophobicity especially resin‐made parts in sample delivery pump, we employed “autodilution” device that provides reliable recovery and repeatability. Additionally, real water samples were collected and then the spiked polycyclic aromatic hydrocarbons were determined at ng/L levels.     

溶胶-凝胶杂化整体柱修饰及在多环芳烃检测中的应用

利用点击反应对含叠氮基的溶胶-凝胶整体柱进行了表面修饰,制备了C₆-硅胶杂化整体萃取柱。实验以多环芳烃为分析对象,考察了制备和修饰条件对萃取效率的影响,在优化的条件下,新制备的整体柱对萘、菲、芘和苯并[a]芘的萃取富集倍数分别达到95.9、114.2、103.2和57.8。萃取实验的日内和日间精密度(RSD)分别小于5.5%(n=8)和7.3%(n=10)。建立的管内固相微萃取-高效液相色谱检测16种常见多环芳烃方法的检出限(S/N=3)达到0.08~3.72 μg/L,定量限(S/N=10)达到0.26~12.40 μg/L。土壤中多环芳烃分析的加标回收率为82.4%~110.6%, RSD为2.6%~7.9%(n=3)。与美国国家环境保护局检测土壤中多环芳烃的方法比较,结果一致,准确性高。实验表明,该方法萃取效率高,灵敏可靠,操作简便,重现性好,可满足土壤等样品中痕量多环芳烃检测的要求。     

Selective solid-phase microextraction of polycyclic aromatic hydrocarbons in water based on oriented phosphorus-containing titanium oxide nanofibers grown on titanium support prior to high-performance liquid chromatography with ultraviolet detection

A novel solid-phase microextraction coating of phosphorous-containing titanium oxide composite was developed using titanium fiber as a support and a titanium source by hydrothermal oxidation in a phosphoric acid solution containing hydrogen peroxide. The morphology of the fiber coatings was controlled by the conditions of the hydrothermal oxidation reaction. The oriented nanofiber coating was employed to extract several types of representative aromatic analytes. The experimental results demonstrated that the as-prepared fiber exhibited excellent extraction efficiency toward polycyclic aromatic hydrocarbons. Combined with high-performance liquid chromatography with ultraviolet detection, main extraction conditions were optimized, including pH, ionic strength, extraction temperature, stirring rate, extraction time and desorption time. The established method presented good linearity from 0.05 to 200 μg/L with limit of detection ranging from 0.012 to 0.126 μg/L. This convenient and green procedure was suitable for the selective extraction and determination of typical polycyclic aromatic hydrocarbons in environmental water samples. The relative recoveries of 85.8–112% were obtained for the determination of target polycyclic aromatic hydrocarbons in water samples spiked with 5.0 and 15.0 μg/L. Moreover, the as-prepared fiber showed at least 210 extraction/desorption cycles due to its high mechanical and chemical stability.     

基于整体柱的固相萃取-高效液相色谱法测定尿液中4种羟基多环芳烃

建立了基于聚合物整体柱的固相萃取-高效液相色谱测定尿液中4种羟基多环芳烃（OH-PAHs）的分析方法。在注射器管中合成聚（甲基丙烯酸丁酯-乙二醇二甲基丙烯酸酯）整体柱（poly （BMA-co-EDMA））,并将其用于尿液中4种羟基多环芳烃的前处理,同时考察了上样浓度、淋洗液、洗脱液和洗脱体积对萃取效率的影响。结合高效液相色谱-荧光分析,4种羟基多环芳烃在各自的范围内线性关系良好（r≥0.9991）;方法的检出限和定量限分别为0.06~0.09 ng/mL和0.20~0.30 ng/mL;日内（n=5）和日间（n=3）精密度分别为1.4%~5.3%和2.6%~7.3%。对焦炉工人尿液样品进行加标（3 ng/mL）回收试验,回收率为78.2%~117.0%。该固相萃取柱能够有效萃取和净化尿液中4种羟基多环芳烃,并且可以重复使用。该法简单、准确,可应用于尿液中羟基多环芳烃的分析。     

固相微萃取/高效液相色谱联用分析食品中痕量苯并咪唑

建立了整体柱固相微萃取/高效液相色谱-紫外联用方法用于食品中6种痕量苯并咪唑的分析。在三元溶剂(N,N-二甲基甲酰胺、对二甲苯和异辛烷)体系下,以4-乙烯基苯硼酸与乙二醇二甲基丙烯酸酯原位聚合法制备了4-乙烯基苯硼酸-乙二醇二甲基丙烯酸酯固相微萃取整体柱,并采用热重分析仪、红外光谱、电镜进行表征。分别研究了萃取溶剂、萃取流速、净化体积、解吸溶剂、解吸流速和解吸体积对富集量的影响。在优化条件下,该方法对苯并咪唑的富集倍数高达1 607~3 015倍,方法的线性范围为0.100~100μg/L,检出限为21~33 ng/L,相对标准偏差(RSD)不大于7.4%。采用该方法分析鱼肉、鸭肉、鸭血和鸭肝样品中的苯并咪唑,加标回收率为75.0%~118%,RSD为1.6%~8.7%。该方法灵敏、准确,能满足食品中痕量苯并咪唑的分析要求。     

Liquid-phase deposition of silica nanoparticles into a capillary for in-tube solid-phase microextraction coupled with high-performance liquid chromatography

A silica nanoparticle (NP)-deposited capillary fabricated by liquid-phase deposition (LPD) and modified with octadecyl groups was introduced for in-tube solid-phase microextraction coupled to high-performance liquid chromatography with UV detection (in-tube SPME–HPLC). The resultant capillary (60 cm × 50 μm I.D.) was demonstrated to be of higher extraction capacity by comparing with an octadecyl-grafted bare capillary and an octadecyl-grafted silica-coated capillary that was prepared by sol–gel chemistry. Two groups of compounds, endocrine disruptors and polycyclic aromatic hydrocarbons, were used as model analytes to further evaluate extraction capacity of the silica NP-deposited capillary, and its reproducibility and stability was also investigated. The extraction time profiles were monitored for all the chemicals, and their limits of detection were calculated to be in the range of 0.42–0.78 and 0.034–0.19 ng/mL with RSD values of peak area less than 4.6%.     

Solid-phase microextraction combined with gas chromatography/triple quadrupole tandem mass spectrometry for determination of nitrated polycyclic aromatic hydrocarbons in sediments

Nitro-polycyclic aromatic hydrocarbons have been detected in various environmental media. However, determination in sediment matrix is challenging due to the lack of a suitable method. In this study, a reliable method for determining 15 nitro-polycyclic aromatic hydrocarbons in sediments was developed based on accelerated solvent extraction and solid-phase microextraction coupled with gas chromatography–tandem mass spectrometry. The accelerated solvent extraction and solid-phase microextraction are sample pre-treatment techniques that have advantages, such as rapid operation and minimal sample volume. Initially, the solid-phase microextraction was optimized using five commercial fibers and from that 65 μm polydimethylsiloxane/divinylbenzene fiber was selected as the best fiber. Further, the accelerated solvent extraction conditions were optimized by Taguchi experimental design, such as extraction temperature (120℃), extraction solvent (dichloromethane), number of cycles (two), static extraction period (4 min), and rinse volume (90%). The method parameters, such as limits of quantitation, and intraday and interday accuracy and precision, were in the range of 0.067–1.57 ng/g, 75.2–115.2%, 69.9–115.4%, and 1.0–16.5%, respectively. Upon meeting all the quality criteria, the method was applied successfully to analyze real sediment samples. Therefore, our study creates a new prospect for the future application of direct immersion solid-phase microextraction in sediment analysis.     

Application of Solid-Phase Microextraction for the Analysis of Nitropolycyclic Aromatic Hydrocarbons in Water

The present work investigates the applicability of solid-phase microextraction coupled to gas-chromatography mass-spectrometry for the determination of trace amounts of nitropolycyclic aromatic hydrocarbons in water samples. The main parameters affecting solid-phase microextraction (sampling mode, fibre type, sampling time, agitation rate and ionic strength of the aqueous solution) were controlled and the optimal experimental conditions found were: 65-μm polydimethylsiloxane-divinylbenzene fibre immersed for 45 min to 5 mL spiked water samples, stirred at 1250 rpm. The developed solid-phase microextraction method was found to be linear in the concentration range 0.1 to 10 μg L⁻¹, with the detection limits ranging between 0.004 and 0.060 μg L⁻¹ (under the selective ion monitoring mode) and the repeatability varying between 1.7 and 5.9% (n=5). Analysis of spiked tap and well water samples revealed that matrix had little effect on extraction. Overall, it was found that solid-phase microextraction is suitable for the trace analysis of nitropolycyclic aromatic hydrocarbons in water samples. Revised: 14 October and 14 November 2005     

Polyurethane foam chips combined with liquid chromatography in the determination of unmetabolized polycyclic aromatic hydrocarbons excreted in human urine

A method suitable for the determination of unmetabolized polycyclic aromatic hydrocarbons (PAHs) excreted at trace levels (ng/L) in human urine for the monitoring of exposure of the general population to PAH contamination was developed. PAHs were determined, after enrichment by solid-phase extraction on polyurethane foam (PUF) chips, by HPLC with fluorescence detection. Different parameters affecting analyte extraction to the PUF, including urine salting-out and organic additives, and optimization of conditions for clean-up and desorption have been investigated. Optimized conditions were 40 mL acidified urine sample, added with magnesium sulfate, tetrahydrofuran and a 2 cm3 PUF chip, and extracted by shaking at 30 rpm for 1 h at ambient temperature. Desorption was performed, after a clean-up step with diluted sodium hydroxide, using a small amount of diethyl ether. The recovery of PAH congeners from spiked urines was >90% in the 2-100 ng/L range; the detection limit was 0.1-0.5 ng/L, depending on the considered PAH congener; day-to-day precision, at 50 ng/L native PAH content, was CV = 10-20%. The proposed technique provides a simple, economical and effective procedure for the determination of trace amounts of unmetabolized PAHs excreted in human urine spot samples.