Optimization and validation of a low temperature microwave-assisted extraction method for analysis of polycyclic aromatic hydrocarbons in airborne particulate matter

A low temperature microwave-assisted extraction method (MAE) is reported for the analysis of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter (PM). The main parameters affecting the extraction efficiency (choice of extractants, microwave power, and extraction time) were investigated and optimized. The optimized procedure requires a 20 ml mixture of acetone:n-hexane (1:1) for extraction of PAHs in PM at 150 W of microwave energy (20 min extraction time). Clean-up of MAE extracts was not found to be necessary. The optimized method was validated using two different SRM (1648-urban particulate matter and 1649a, urban dust). The results obtained are in good agreement with certified values. PAHs recoveries for both reference materials were between 79 and 122% with relative standard deviation ranging from 3 to 21%. Detection limits were determined based on blank determination using two kinds of quartz filter substrates (n = 10), which ranged from 0.001 (0.03) ng m⁻³ (pg/μg) for B(k)Ft to 1.119 (37.3) for Naph in ng m⁻³ (pg/μg), respectively. The repeatability and day-to-day reproducibility obtained in this study were in the range of 4-16 and 3-25% for spiked standards and SRM 1649, respectively. The optimized and validated MAE technique was applied to the extraction of PAHs from a set of real world PM samples collected in Singapore. The sum of particulate-bound PAHs in outdoor PM ranged from 1.05 to 3.45 ng m⁻³ while that in indoor PM (cooking emissions) ranged from 27.6 to 75.7 ng m⁻³, respectively.     

Thermal desorption gas chromatography–mass spectrometry as an enhanced method for the quantification of polycyclic aromatic hydrocarbons from ambient air particulate matter

Polycyclic aromatic hydrocarbons (PAHs) from ambient air particulate matter (PM) were analysed by a two-step thermal desorption (TD) injection system integrated to a gas chromatograph–mass spectrometer (GC/MS). The operational variables of the TD method were optimised and the analytical expanded uncertainties were calculated to vary from 8% to 16% over the operative concentration range (40–4000 pg). The performance of the TD method was validated by the analysis of a standard reference material and by comparison of PAH concentrations in PM samples to those obtained by a conventional liquid extraction (LE) method. The TD method reported lower uncertainties than the LE method for the analysis of similar concentrations in air. The TD method also showed advantages for shorter sampling times in comparison to 24 h for source apportionment applications and for reducing losses of more reactive compounds such as benzo[a]pyrene.     

Ultrasound-assisted extraction and on-line LC–GC–MS for determination of polycyclic aromatic hydrocarbons (PAH) in urban dust and diesel particulate matter

A method has been developed for determination of polycyclic aromatic hydrocarbons (PAH) in particulate matter from ambient air and diesel exhaust emissions. It is reproducible and accurate and, compared with similar methods for analysis of individual PAH components in complex matrices, it is relatively fast and simple. Single PAH components can be determined in samples of particulate matter from ambient air and diesel exhaust emissions with LOD of approximately 1 pg/sample. Further, sample throughput is high, because more than 20 samples can be extracted and prepared for analysis in one working (8-h) day. The particulate matter is subjected to ultrasound-assisted extraction, a technique that is shown to extract PAH from particulate material with efficiencies fully comparable with those of Soxhlet extraction. An aliphatic/PAH-enriched fraction is obtained by solid-phase extraction before isolation, separation, and identification/quantification of PAH by on-line liquid chromatography–gas chromatography–mass spectrometry. The method was validated by analysis of US National Institute of Standards and Technology (NIST) Standard Reference Materials (SRM) 1649a, Urban Dust, and 2975, Diesel Particulate Matter. Results from the method are in good agreement with the NIST-certified PAH concentrations and with NIST reference PAH concentrations.     

固相微萃取-气相色谱法测定红葡萄酒中残留的有机磷农药

采用溶胶-凝胶包埋技术制备了耐高温固相微萃取头(SPME),用该萃取头与气相色谱-热离子化检测器联用对红葡萄酒中的12种有机磷农药残留进行了测定。实验中对搅拌速度、萃取时间、盐浓度等条件进行了优化。结果表明,在样品用量25 mL,搅拌速度1250 r/min,盐浓度 150 g/L,萃取时间30 min的条件下,绝大多数组分峰面积的相对标准偏差（RSD）在5%以下,各种有机磷农药的检测限为5 ng/L到0.38 μg/L。     

Polyvinylimidazole/sol–gel composite as a novel solid‐phase microextraction coating for the determination of halogenated benzenes from aqueous solutions

A polyvinylimidazole/sol–gel composite is proposed as a novel solid‐phase microextraction fiber to extract five halobenzenes from the headspace of aqueous solutions in combination with gas chromatography with mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The obtained results showed that porous polyvinylimidazole/sol–gel composite was chemically deposited on fused silica fiber. The effect of important extraction parameters including extraction temperature, extraction time, and salt content were investigated. The optimum conditions were as follows: extraction temperature 25°C, extraction time 20 min, and salt concentration 30 w/v%. Detection limits and relative standard deviations of the developed method for halogenated benzenes were below 0.1 pg/mL and 15%, respectively. Repeatability of the proposed method, explained by relative standard deviation, varied between 5.48 and 9.15% (n = 5). The limits of detection (S/N = 3) ranged between 0.01 and 0.10 ng/L using gas chromatography with mass spectrometry with selected ion monitoring mode. For real sample analysis, three types of water samples with different matrices (ground, surface, and tap water) were studied. The optimized procedure was applied to extraction and method validation of halogenated benzenes in spiked water samples.     

Trace analysis of polycyclic aromatic hydrocarbons in suspended particulate matter by accelerated solvent extraction followed by gas chromatography–mass spectrometry

An analytical procedure based on extraction by accelerated solvent extraction (ASE) followed by gas chromatography–mass spectrometry (GC/MS) analysis has been developed for the determination of particulate polycyclic aromatic hydrocarbons (PAHs) from large-volume water samples (20 L). The effect of temperature and number of cycles on the efficiency of ASE was investigated: the best results were obtained by using a temperature of 100°C and one static cycle. A mixture of hexane/acetone 1:1 (v/v) was used as extraction solvent. Mean total method recovery under optimized conditions was 85%. The developed methodology was applied to the analysis of suspended particulate matter from Lake Maggiore waters (north of Italy). Mean PAH concentrations in suspended particulate matter from Lake Maggiore ranged from 0.2 ng L⁻¹ for anthracene to 18.7 ng L⁻¹ for naphthalene.     

Rapid determination of inorganic elements in airborne particulate matter by using acidified subcritical-water extraction and inductively-coupled plasma–optical-emission spectrometry

A rapid and simple method has been developed for determination of inorganic elements in airborne particulate matter (PM10) by using acidified subcritical water and ICP–OES. Elements such as Al, As, B, Ba, Cd, Cu, Fe, Mn, Pb, Se, and Zn were rapidly and efficiently extracted from PM10 samples with a solution of 0.1 mol L^–1 HNO₃ under subcritical conditions. The method requires approximately 5% of the amount of acid used in the standard microwave extraction procedure. The material selected for the subcritical extraction manifold was poly ether ether ketone (PEEK), to avoid sample contamination with elements present in previously reported stainless-steel manifolds. The extraction temperature, time of static and dynamic extraction, and flow rate of acidified water were studied keeping the pressure controlled at about 1,500 psig. The efficiency of extraction of most of the analytes increased with temperature, tending to quantitative extraction at temperatures near 150°C. After the extraction process the analytes were determined directly in the extract by ICP–OES. When the method was compared with the USEPA counterpart, the results indicate that under optimized conditions (static extraction time: 15 min, dynamic extraction time: 30 min, flow rate: 2 mL min^–1) the analytes were extracted with recoveries between 73 and 158%. Alternatively, by using an extraction time of 15 min, the method could be used to screen for all the elements, with recoveries over 50%. The developed method was applied to the determination of inorganic elements in airborne particulate matter in the atmosphere of Santiago, Chile.     

Analysis of polycyclic aromatic hydrocarbons in atmospheric particulate samples by microwave‐assisted extraction and liquid chromatography

A methodology based on microwave‐assisted extraction (MAE) and LC with fluorescence detection (FLD) was investigated for the efficient determination of 15 polycyclic aromatic hydrocarbons (PAHs) regarded as priority pollutants by the US Environmental Protection Agency and dibenzo(a,l)pyrene in atmospheric particulate samples. PAHs were successfully extracted from real outdoor particulate matter (PM) samples with recoveries ranging from 81.4 ± 8.8 to 112.0 ± 1.1%, for all the compounds except for naphthalene (62.3 ± 18.0%) and anthracene (67.3 ± 5.7%), under the optimum MAE conditions (30.0 mL of ACN for 20 min at 110°C). No clean‐up steps were necessary prior to LC analysis. LOQs ranging from 0.0054 ng/m³ for benzo(a)anthracene to 0.089 ng/m³ for naphthalene were reached. The validated MAE methodology was applied to the determination of PAHs from a set of real world PM samples collected in Oporto (north of Portugal). The sum of particulate‐bound PAHs in outdoor PM ranged from 2.5 and 28 ng/m³.     

Liquid chromatography-tandem mass spectrometry analysis of 17α-trenbolone, 17β-trenbolone and trendione in airborne particulate matter

Trenbolone acetate (TbA) is a potent synthetic anabolic steroid that was approved by the FDA as a growth promoter in beef cattle in 1987. Given the endocrine-modulating activity of TbA and its metabolites in all vertebrates, a sensitive and reliable analytical method is needed to detect TbA and related residues in environmental matrices. We have developed a method that incorporates solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of the three major TbA metabolites (trendione, 17β-trenbolone, 17α-trenbolone) in total suspended particulate matter (TSP) samples. Sample preparation involved pressurized liquid extraction followed by cleanup on solid-phase extraction cartridges. The procedure was optimized to obtain maximum recovery and minimum signal suppression/enhancement from matrix effects. Analytes were separated with a Phenomenex Gemini-NX C18 analytical column (150 mm × 2.0 mm, 3 μm particle size) using an aqueous methanol gradient at a flow rate of 0.2 mL/min. Column effluent underwent positive electrospray ionization (ESI). Two or more diagnostic product ions were acquired from analyte specific precursor ions for unambiguous confirmation and quantification. The method detection limit was 3.27-4.87 ng/g of particulate matter (PM). Method accuracy, determined with analyte recoveries, ranged between 68% and 117%, and method precision, expressed as relative standard deviation, was below 15% at spiked levels of 6.67, 33.3, and 167 ng/g PM. Analysis of TSP samples demonstrated the presence of the target species associated with PM in the vicinity of beef cattle feeding operations.     

Determination of dibenzopyrenes in standard reference materials (SRM) 1649a, 1650, and 2975 using ultrasonically assisted extraction and LC–GC–MS

A method has been developed for analysis of the highly potent polycyclic aromatic hydrocarbon (PAH) carcinogens dibenzo(a,l)pyrene, dibenzo(a,h)pyrene, and dibenzo(a,i)pyrene (molecular weight 302) present in small amounts in diesel and air particulate material. The method can also be used for analysis of the PAH benzo(a)pyrene, coronene, and perylene, for which reference and certified values are available for the standard reference materials used for validation of the method—SRM 1649a (urban dust) and SRM 2975 (diesel particulate matter). The only NIST values that have been published for these dibenzopyrene isomers in the analyzed SRM are reference values for dibenzo(a,i)pyrene and dibenzo(a,h)pyrene in SRM 1649a. The concentrations determined in the SRM were in good agreement with reported NIST-certified and reference values and other concentrations reported in the literature. Standard reference material 1650 (diesel particulate matter) was also analyzed. The method could not, however, be validated using this material because certification of SRM 1650 had expired. The method is based on ultrasonically assisted extraction of the particulate material, then silica SPE pre-separation and isolation, and, separation and detection by hyphenated LC–GC–MS. The method is relatively rapid and requires only approximately 1–5 mg SRM particulate material to identify and quantify the analytes. Low extraction recoveries for the analytes, in particular the dibenzopyrenes, when extracting diesel SRM 2975 and 1650 resulted, however, in the dibenzopyrenes being present in amounts near their limits of quantifications in these samples. The method’s limit of quantification (LOQ), based on analyses of SRM 1649a, is in the range 10–77 pg. By use of this method more than 25 potential PAH isomers with a molecular weight of 302 could be separated.     

Static subcritical water extraction with simultaneous solid-phase extraction for determining polycyclic aromatic hydrocarbons on environmental solids

A rapid and very simple method for extracting polycyclic aromatic hydrocarbons (PAHs) from soils, sediments, and air particulate matter has been developed by coupling static subcritical water extraction with styrene-divinylbenzene (SDB-XC) extraction discs. Soil, water, and the SDB-XC disc are placed in a sealed extraction cell, heated to 250 degrees C for 15 to 60 min, cooled, and the PAHs recovered from the disc with acetone/methylene chloride. If the cells are mixed during heating, all PAHs with molecular weights from 128 to 276 are quantitatively (>90%) extracted and collected on the sorbent disc and are then recovered by shaking with acetone/methylene chloride. After water extraction, the sorbent discs can be stored in autosampler vials without loss of the PAHs, thus providing a convenient method of shipping PAH extracts from field sites to the analytical laboratory. The method gives good quantitative agreement with standard Soxhlet extraction, and with certified reference materials for PAH concentrations on soil, sediment (SRM 1944), and air particulate matter (SRM 1649a).     

GC/MS analysis of water-soluble organics in atmospheric aerosol: optimization of a solvent extraction procedure for simultaneous analysis of carboxylic acids and sugars

The main goal of the present study was to develop a procedure for the simultaneous GC/MS analysis of a wide range of water-soluble organic compounds (WSOCs, mainly dicarboxylic acids and sugars) in atmospheric aerosol as chemical markers of atmospheric processes. The response surface methodology, including central composite design, was applied to systematically investigate and optimize the operating conditions of a solvent extraction method as the most widely used procedure for determining WSOCs in particulate matter (PM) samples. A solvent mixture of methanol/dichloromethane (90:10) and a volume of 10 ml were the optimum conditions that permit the simultaneous analysis of 30 target WSOCs, including dicarboxylic acids and sugars. Recoveries and limits of detection were determined for a standard mixture containing target analytes, and they varied from 79 to 103 % and 0.3 to 1 ng?m^?3, respectively. The optimized procedure was used for the analysis of field PM filters and demonstrated its feasibility in detecting several important environmental WSOCs.     

Determination of polycyclic aromatic hydrocarbons and their oxy-, nitro-, and hydroxy-oxidation products

A sensitive method has been developed for the trace analysis of PAHs and their oxidation products (i.e., nitro-, oxy-, and hydroxy-PAHs) in air particulate matter (PM). Following PM extraction, PAHs, nitro-, oxy-, and hydroxy-PAHs were fractionated using solid phase extraction (SPE) based on their polarities. Gas chromatography–mass spectrometry (GC–MS) conditions were optimized, addressing injection (i.e., splitless time), negative-ion chemical ionization (NICI) parameters, i.e., source temperature and methane flow rate, and MS scanning conditions. Each class of PAH oxidation products was then analyzed using the sample preparation and appropriate ionization conditions (e.g., nitro-PAHs exhibited the greatest sensitivity when analyzed with NICI–MS while hydroxy-PAHs required chemical derivatization prior to GC–MS analysis). The analyses were performed in selected-ion-total-ion (SITI) mode, combining the increased sensitivity of selected-ion monitoring (SIM) with the identification advantages of total-ion current (TIC). The instrumental LODs determined were 6–34 pg for PAHs, 5–36 pg for oxy-PAHs, and 1–21 pg for derivatized hydroxy-PAHs using electron ionization (GC-EI-MS). NICI–MS was found to be a useful tool for confirming the tentative identification of oxy-PAHs. For nitro-PAHs, LODs were 1–10 pg using negative-ion chemical ionization (GC-NICI-MS). The developed method was successfully applied to two types of real-world PM samples, diesel exhaust standard reference material (SRM 2975) and wood smoke PM.     

Optimization and determination of polycyclic aromatic hydrocarbons in biochar‐based fertilizers

The agronomic benefit of biochar has attracted widespread attention to biochar‐based fertilizers. However, the inevitable presence of polycyclic aromatic hydrocarbons in biochar is a matter of concern because of the health and ecological risks of these compounds. The strong adsorption of polycyclic aromatic hydrocarbons to biochar complicates their analysis and extraction from biochar‐based fertilizers. In this study, we optimized and validated a method for determining the 16 priority polycyclic aromatic hydrocarbons in biochar‐based fertilizers. Results showed that accelerated solvent extraction exhibited high extraction efficiency. Based on a Box–Behnken design with a triplicate central point, accelerated solvent extraction was used under the following optimal operational conditions: extraction temperature of 78°C, extraction time of 17 min, and two static cycles. The optimized method was validated by assessing the linearity of analysis, limit of detection, limit of quantification, recovery, and application to real samples. The results showed that the 16 polycyclic aromatic hydrocarbons exhibited good linearity, with a correlation coefficient of 0.996. The limits of detection varied between 0.001 (phenanthrene) and 0.021 mg/g (benzo[ghi]perylene), and the limits of quantification varied between 0.004 (phenanthrene) and 0.069 mg/g (benzo[ghi]perylene). The relative recoveries of the 16 polycyclic aromatic hydrocarbons were 70.26–102.99%.     

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.     

Development and validation of capillary electrophoresis for the determination of selected metal ions in airborne particulate matter after sequential extraction

A capillary electrophoresis (CE) method has been developed and validated for the determination of the distribution of metals in particulate matter after three-stage sequential extraction. Fe(II), Zn(II), Cu(II), Mn(II), and Cd(II) ions were separated using a background electrolyte consisting of 200 mmol L(-1) ammonium acetate (pH 5.5), 0.5 mmol L(-1) 1,10-phenanthroline, 10 mmol L(-1) hydroxylamine hydrochloride, and 20% acetone. The method was validated with respect to specificity, linearity, detection limits, precision, and accuracy. Detection limits are at sub-microg L(-1) levels (tens of microg g(-1) of particulate matter) using pressure injection. The analytical procedure was checked by analyzing a standard reference material, NIST SRM 1648 Urban Particulate Matter.     

Developing a miniaturized setup for in‐tube simultaneous determination of three alkaloids using electromembrane extraction in combination with ultraviolet spectrophotometry

Herein, electromembrane extraction was combined with ultraviolet spectrophotometry using a customized manifold for preconcentration and simultaneous determination of morphine, codeine, and papaverine in water and human urine samples. Absorption spectra of the extracts were recorded inside the lumen of the hollow fiber using two fiber optics connected to a miniature spectrophotometer. Partial least squares regression was applied to resolve the overlapped spectra of the analytes. Performance of the model was validated by an independent test set. Central composite design was applied to optimize the extraction parameters. The optimized extraction conditions are as follows; supporting liquid membrane: 2‐nitrophenyl octyl ether containing 15% v/v bis(2‐ethylhexyl) phosphate, applied voltage: 80 V, donor pH: 3.0, acceptor pH: 1.0, extraction time: 20 min. Finally, the optimized extraction method was validated for determination of the mentioned alkaloids in human urine samples. The method showed good linearity (R² > 0.995) for all of the mentioned alkaloids. The limits of detection for morphine, codeine, and papaverine in diluted human urine were found to be 0.6, 1.1, and 0.6 ng/mL, respectively with acceptable relative standard deviations. Enrichment factors of 104, 108, and 102 were achieved for morphine, codeine, and papaverine, respectively.     

Optimization and validation of a capillary electrophoresis methodology for inorganic anions in atmospheric aerosol samples

Optimization and validation of a method for the determination of inorganic anions, such as chloride, nitrate, sulphate, fluoride and phosphate, in atmospheric particulate matter is described. Ultrasonic extraction followed by CE, using CTAB as EOF modifier, has been established for this separation using chromate as visualization reagent for the indirect UV/vis detection. Optimization of the experimental chemical conditions (pH, surfactant concentration, chromate concentration and acetonitrile concentration) and instrumental parameters (temperature, applied voltage and injection time) is described. Linear calibrations plots are obtained for the five ions, with detection limits in the high ng/mL range. A standard reference material, SRM 1648 Urban Particulate Matter, has been used to validate the proposed method. Satisfactory reproducibility and acceptable agreement to the matter atmospheric samples has been found (recoveries ranging from 86 to 96%). Application to real particulate matter atmospheric samples, collected on high volume samplers from the air quality surveillance network of Extremadura, southwest Spain, is shown.     

快速溶剂提取-高效液相色谱法测定PM2.5中16种多环芳烃

建立大气细颗粒物(PM2.5)中16种多环芳烃(PAHs)的快速溶剂提取-直接进样-高效液相色谱测定方法.PM2.5经玻璃纤维滤膜收集,采样后的滤膜直接用乙腈经快速溶剂萃取仪提取,以乙腈和水作为流动相,提取液通过ZORBAX Eclipse PAH液相色谱柱分离,紫外串联荧光检测器检测.16种PAHs分离效果良好,在0.025~5.000μg/mL范围内线性相关系数r≥0.9998,方法加标回收率为78.3%~113.2%,相对标准偏差为0.5%~9.5%,检出限为0.007~0.062 ng/m3.本方法操作简便、快速、准确、灵敏,适于PM2.5中16种PAHs的同时测定.     

Application of solid-phase microextraction and gas chromatography-mass spectrometry for the determination of chlorophenols in leather

This paper proposes a new analytical procedure based on the headspace solid‐phase microextraction (HS‐SPME) technique and gas chromatography‐selected ion monitoring‐mass spectrometry (GC‐SIM‐MS) for the determination of 16 phenols extracted from leather samples. The optimized conditions for the HS‐SPME were obtained through two experimental designs – a two‐level fractional factorial design followed by a central composite design – using the commercial SPME fiber polyacrylate 85 μm (PA). The best extraction conditions were as follows: 200 μL of derivatizing agent (acetic anhydride), 20 mL of saturated aqueous NaCl solution and extraction time and temperature of 50 min and 75°C, respectively. All optimized conditions were obtained with fixed leather sample mass (250 mg), vial volume (40 mL) and phosphate buffer pH (12) and concentration (50 mmol/L). Detection limits ranging from 0.03 to 0.20 ng/g, and relative standard deviation (RSD) lower than 10.23% (n=6) for a concentration of 800 ng/g (chlorophenols) and 1325 ng/g (2‐phenylphenol) in the splitless mode were obtained. The recovery was studied at three concentration levels by adding different amounts of phenols to the leather sample and excellent recoveries ranging from 90.0 to 107.2% were obtained. The validated method was shown to be suitable for the quantification of phenols in leather samples, as it is simple, relatively fast and sensitive.