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.     

Development of an analytical method for the simultaneous determination of 15 carcinogenic polycyclic aromatic hydrocarbons and polycyclic aromatic nitrogen heterocyclic compounds. Application to diesel particulates

A new method enabling the determination of 15 priority carcinogenic polyaromatic compounds (PAC) proposed by the US National Toxicology Program (NTP) has been developed and applied to diesel exhaust particulates (DEP). The clean-up procedure consists of solid-phase extraction (SPE) and HPLC fractionation on silica phases followed by liquid-liquid extraction and chromatography on a polyvinylbenzene copolymer column. The method gives good recoveries for all PAC studied except dibenzo[a,j]acridine and dibenzo[a,h]pyrene, for which recovery values are below 80%. The use of GC-MS ion trap and its capacity to achieve single-ion storage enhanced the sensitivity of the method, enabling the detection of high-molecular-weight PAH in the low ng g(-1) concentration range. Intermediate polarity GC columns, e.g. BPX-50 or equivalent, enabled better separation, when applied to DEP analysis, than the generally used DB-5 apolar phase. This is observed mainly for separation of isomeric compounds belonging to the benzofluoranthene and dibenzopyrene families. The application of this method to DEP sampled from the exhaust of a diesel engine and in confined locations such as a tunnel has shown that all PAH of the NTP list could be detected, except dibenzo[a,h]pyrene. No dibenzacridine or dibenzocarbazole could be detected in such matrices. The method is sufficiently sensitive to be applicable to environmental exposure measurements in occupational health surveys.     

Uncertainties of polynuclear aromatic hydrocarbon and carbonyl measurements in heavy-duty diesel emission

In this note we describe the speciated particle-phase PM2.5 polynuclear aromatic hydrocarbon (PAH) and gas-phase carbonyl emissions as collected from a heavy-duty diesel bus outfitted with an oxidation catalyst for exhaust after-treatment. The vehicle was run on a chassis dynamometer during a transient cycle test reproducing a typical city bus route (Azienda Tramviaria Municipalizzata cycle). The diluted tailpipe emissions were sampled for PAH using a 2.5 microm cut size cyclone glass fiber filter assembly, while carbonyls were absorbed onto dinitrophenyl hydrazine-coated silica cartridges. The former compounds were analysed by CGC-MS, the latter by HPLC-UV. Combining the two sets of speciation data resulting from 15 identical dynamometer tests provided a profile of both unregulated organic emissions. PAH emission rates decreased with the number of benzene fused rings. Fluoranthene and pyrene amounted to 90% of total PAHs quantified; six-ring PAHs accounted only for 0.5%. Similarly, formaldehyde and acetaldehyde accounted for approximately 80% of the total carbonyl emissions. Uncertainties of the method in the determination of individual emission factors were calculated. Statistical data processing revealed that all the measurements were quite unaffected by systematic errors and repeatability percentages did not exceed 50% for the majority of components of both groups.     

Selective determination of substituted PAH in aerosols using liquid CO2-extraction,HPLC prefractionation on chemically activated silica,and HRGC combined with negative ion mass spectrometry

A method is described which allows the determination of different substituted polycyclic aromatic hydrocarbons (PAH) such as NO₂-PAH, carbazoles, keto-PAH, and aza-arenes in aerosol samples. Liquid CO₂-extraction is used to minimize the loss of reactive compounds. High performance liquid chromatography on chemically activated silica is employed to prefractionate the samples into subfractions with a minimum of overlap between different PAH compound classes. Both electron capture detection and negative ion chemical ionization combined with capillary gas chromatography are used for identification and quantification. The latter method also allows distinction between isomers with different toxic properties when N₂O/CH₄ reaction gas mixtures are used. Selectivity for tetrachlorodibenzo-p-dioxins as against pesticides and polychlorinated biphenyls can be improved by this technique. The applicability of the method is critically discussed and different examples are given.     

S_2OF_(10)气体标准样品制备方法和测定方法研究

提出了一系列的安全、方便、可靠、在线和可连续操作的热解吸／色谱分析柱制备Ｓ２ＯＦ１０纯品、指数稀释法配制Ｓ２ＯＦ１０标准样品、应用定量校正系数测定样品中痕量Ｓ２ＯＦ１０的方法和技术。分别采用气相色谱、红外光谱、气相色谱／质谱等方法对色谱制备的Ｓ２ＯＦ１０纯品进行了纯度分析和测定。配制Ｓ２ＯＦ１０标准气体的体积分数范围为８．０×１０－７～２．６×１０－４。气相色谱测定Ｓ２ＯＦ１０的定量校正系数为０．１９７,测定方法的相对误差范围为１．８％～２０％。     

Large sample injection method (≥ 100 μL) for capillary GC using a commercial thermodesorption unit as injection device

A commercial thermodesorption and cold trap unit can be used as a large sample volume injection device in high resolution gas chromatography. Volumes of more than 100 μl can be injected. More than 97% of solvents, such as hexane, can be removed by a Tenax TA precolumn without any loss of compounds with volatilities comparable to naphthalene. Experimental conditions, recovery rates of polycyclic aromatic hydrocarbons, and the reproducibility of the method are described in detail. The method was successfully applied for the determination of PAH in air particulate matter extracts.     

Pilot study: PAH fingerprints of aircraft exhaust in comparison with diesel engine exhaust

In the course of a preliminary investigation the PAH fingerprints from diesel engines were compared with those from aircraft turbines. The goal was to determine whether PAH fingerprints permit to distinguish between the sources of air and road traffic. The results showed that the PAH spectra of both sources do not vary significantly. However, in turbine exhaust gas p-quaterphenyl was found, that is untypical for diesel engines. So this component may be a tracer for PAH pollution from aeroplanes.     

Rapid determination of polycyclic aromatic hydrocarbons in the exhaust gases of direct-injecting Diesel engines by HPLC

A rapid HPLC procedure is introduced that allows the quantification of polycyclic aromatic hydrocarbons (PAH) in the exhaust gases of direct injecting Diesel engines. A branch stream of the motor exhaust gas is passed through a cooler and a filter. Then the cooler rinsing phase and the soot collected on the filter are extracted with toluene. The clean-up is carried out by solid phase extraction and thin-layer chromatography. Using this method, which is reproducible with high precision, a great number of samples may be analysed in a cost and time efficient manner, even when other rapid procedures fail.     

Analysis of heavy organic pollutants of confined atmospheres

Summary An improved procedure for the determination of the less volatile air pollutants of recycled closed atmospheres by activated carbon-Soxhlet extraction is proposed. After total treatment of desorbate, PAH determination is then accomplished by RP-HPLC using both adsorptiometric and fluorimetric UV detection; phenolic compounds are determined by GC-MS.This technique is suitable for very low levels of PAH and phenolic compounds.     

The identification of nitrated polycyclic aromatic hydrocarbons in diesel particulate extracts and their potential formation as artifacts during particulate collection

Summary The highly complex matrix of diesel particulate extracts was analyzed for nitrated polycyclic aromatic hydrocarbons (nitro-PAH) using fused-silica capillary-column gas chromatography along with a thermionic nitrogen-phosphorus detector (TID) and high-performance liquid chromatography followed by on-line catalytic reduction of the nitro-PAH to amino-PAH and subsequent fluorescence detection. Positive isomer identification and quantitation of nitro-PAH are from retention times of authentic standards and their mass spectra. The ease of nitro-PAH formation by nitration of PAH raises the question regarding the origin of these species, whether they are produced as “native” products during the engine combustion process and/or in the exhaust, or instead, formed as the result of chemical conversion to produce artifacts during the sampling procedure. This problem is assessed examing 1-nitropyrene-concentration in particulates of three light-duty diesel engines for different sampling times. 1-Nitropyrene concentrations show only a moderate increase with sampling time under average sampling conditions. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Direct determination of nickel in gas oil by atomic absorption spectrometry with electrothermal atomization

A rapid graphite-furnace atomic absorption procedure with simple dilution of samples was tested for the direct determination of sub-ppm levels of nickel in gas oils. The selection of appropriate graphite-furnace parameters, the type of solvent and organometallic standard, the effect of gas oil concentration in diluted samples, precision, accuracy and detection limit were investigated. Sample dilution was necessary because of high viscosity. Results obtained by standard addition for heavy gas oils were confirmed by a wet-ashing flame atomic absorption procedure. The relative standard deviation (r.s.d.) for consecutive determinations of nickel in gas oil solution containing 19 μg Ni l^?1 was 3.1%, and day-to-day r.s.d. for a reference gas oil sample was 5.3%. Accuracy was determined with an NBS standard reference oil GM-5 (4.6 ± 4.7% relative error in four determinations). Recovery experiments gas 104 ± 12% of the added nickel.     

Sample preparation methods for subsequent determination of metals and non-metals in crude oil—A review

In this review sample preparation strategies used for crude oil digestion in last ten years are discussed focusing on further metals and non-metals determination. One of the main challenges of proposed methods has been to overcome the difficulty to bring crude oil samples into solution, which should be compatible with analytical techniques used for element determination. On this aspect, this review summarizes the sample preparation methods for metals and non metals determination in crude oil including those based on wet digestion, combustion, emulsification, extraction, sample dilution with organic solvents, among others. Conventional methods related to wet digestion with concentrated acids or combustion are also covered, with special emphasis to closed systems. Trends in sample digestion, such as microwave-assisted digestion using diluted acids combined with high-efficiency decomposition systems are discussed. On the other hand, strategies based on sample dilution in organic solvents and procedures recommended for speciation analysis are reported as well as the use of direct analysis in view of the recent importance for crude oil field. A compilation concerning sample preparation for crude oil provided by official methods as well as certified reference materials available for accuracy evaluation is also presented and discussed.     

Pilot study: PAH fingerprints of aircraft exhaust in comparison with diesel engine exhaust

In the course of a preliminary investigation the PAH fingerprints from diesel engines were compared with those from aircraft turbines. The goal was to determine whether PAH fingerprints permit to distinguish between the sources of air and road traffic. The results showed that the PAH spectra of both sources do not vary significantly. However, in turbine exhaust gas p-quaterphenyl was found, that is untypical for diesel engines. So this component may be a tracer for PAH pollution from aeroplanes. Received: 7 February 1997 / Revised: 24 September 1997 / Accepted: 27 September 1997     

Trace gas analysis for the evaluation of zero air generators

Trace amount of substance fractions of air pollutants in zero air are measured applying sensitive analytical methods in combination with the infrastructure to operate zero air generators under simulated field conditions at place. The uncertainties of the amount of substance fractions of a diluted standard gas mixture and the dilution offsets are calculated under conditions that consider the effect of trace amounts of analyte in the zero gas with increasing dilution of a gravimetric gas standard. The analytical methods and their calibration, the test procedure and results for various zero air generators are described. The results are compared with the specifications, the Swiss regulatory requirements and the European norms for monitoring ambient air pollutants. By knowing the residual amount of substance of the analyte in a zero gas, the instrument offsets by dilution can be eliminated and the uncertainties for the measurement values of the diluted standard gas mixtures be calculated.     

Modeling nucleation and coagulation modes in the formation of particulate matter inside a turbulent exhaust plume of a diesel engine

This paper presents the results from a study that is aimed at predicting the nucleation, coagulation, and dynamics of particulate matter (PM) emissions from on-road heavy-duty diesel vehicles. The PM concentration is predicted from the composition of fuel, and operating and ambient conditions. A numerical algorithm for simultaneously solving the coagulation, condensation, and nucleation equations is developed. The effect of relative humidity on the nucleation rate and the nucleus size is also discussed. In addition, the effect of the ambient air dilution on PM size distribution is numerically predicted for a diesel-powered truck operating in a controlled environment at NASA Langley wind-tunnel facility. The particle size distribution and concentration are measured at four different locations in a turbulent plume from the diesel exhaust in the tunnel, and an excellent agreement between the measured and predicted PM concentration values at these locations inside the tunnel is observed.     

Fluorimetric flow-injection analysis of total amounts of aldehydes in auto exhaust gas and thermal degradation emission gas with cyclohexane-1,3-dione

A simple flow-injection (FI) spectrofluorimetric method for the assay of total volatile aldehydes in auto exhaust gas and emission gas from thermal degradation was developed. Aldehydes, such as formaldehyde, acetaldehyde, propionaldehyde and n-butyraldehyde, reacted with cyclohexane-1,3-dione (CHD) to form more strongly fluorescent compounds. A two-channel flow system was assembled. Distilled water and 0.02% CHD were delivered at 0.75 ml min(-1). The optimum conditions were pH 5 (2.2 M CH(3)COONH(4)-CH(3)COOH buffer solution), reaction temperature 70 degrees C, reaction coil length 0.5 mm i.d. x 7 m, cooling coil length 2 m, sample size 60 microl, excitation and emission wavelengths, 376 nm and 452 nm. Aldehydes in sample gas (10 1) were collected by passing the gas at a flow rate of 0.5 1 min(-1) through two impingers connected in series. 10 ml of methanol was used as an absorbent and diluted sample solution was injected into the carrier stream. The calibration graph was linear in the range 100-1000 ppb. The detection limit was 30 ppb and a sampling frequency of 30 h(-1) was attained. Relative standard deviation for 10 standard formaldehyde solutions (500 ppb) was 1.5%. This rapid and simple FI method was applied to the determination of the total amount of aldehydes, calculated as formaldehyde, in auto exhaust gas and emission gas from the thermal degradation of polymers. The method is useful for monitoring aldehyde emissions and investigating the removal effect of aldehydes from various sources.     

The Application of Perdeuterated Polycyclic Aromatic Hydrocarbons (PAH) as Internal Standards for the Liquid Chromatographic Determination of PAH in a Petroleum Crude Oil and Other Complex Mixtures

Abstract

A sequential liquid chromatographic (LC) procedure for the determination of polycyclic aromatic hydrocarbons (PAH) in a petroleum crude oil and other complex mixtures is described. The procedure includes normal-phase LC on an aminosilane column to isolate fractions containing isomeric PAH and reversed-phase LC on a polymeric C₁₈ column to separate the individual PAH isomers. Appropriate perdeuterated PAH are added to the sample so that each isomeric fraction will contain one internal standard. The perdeuterated PAH are excellent internal standards for this sequential LC procedure. Perdeuterated PAH have normal-phase and reversed-phase LC retention characteristics similar to those of the parent PAH. In the normal-phase LC separation, the perdeuterated PAH elute in the same fraction as the parent PAH. In the reversed-phase LC separation, the perdeuterated PAH elute first and are generally resolved from the parent PAH. The optimized spectrofluorometric detection of each PAH analyte is accomplished by programming appropriate sets of excitation and emission wavelengths to correspond with the elation time of each analyte on the polymeric C₁₈ column. The analytical results obtained from this procedure for the analysis of a shale oil sample [Standard Reference Material (SRM) 1580] and a petroleum crude oil (SRM 1582) are compared to values obtained by gas chromatography - mass spectrometry.     

Determination of mannose in honey by isotope dilution gas chromatography mass spectrometryEI北大核心CSCD

建立了一种同位素稀释-气相色谱/质谱(GC-MS)测定蜂蜜中甘露糖含量的方法。选择了一种新型化合物[13C;D]-D-甘露糖作为蜂蜜中甘露糖检测的同位素内标,优化了甘露糖及其内标的气相色谱分离条件和质谱参数。蜂蜜样品经70%乙醇水溶液溶解后加入同位素内标,采用两步衍生法对蜂蜜中糖组分进行衍生化,即先加入2.5%盐酸羟胺-吡啶溶液进行肟化衍生,再加入N,O-双(三甲基硅基)三氟乙酰胺(BSTFA)进行硅烷化衍生,采用GC-MS对甘露糖进行定性分析和定量检测。结果表明,以洋槐蜜、油菜蜜、荆条蜜和椴树蜜为代表性样品基质,甘露糖的检出限均为6 mg/kg,定量限为20 mg/kg,在20,40,200 mg/kg 3个添加水平下方法的平均回收率在66.1%~91.7%之间,相对标准偏差不超过20%。该方法适用于不同类型蜂蜜中甘露糖含量的测定。     

Extension of the dynamic range of flame atomic absorption spectrometry using flow injection analysis with variable-volume dilution chambers

A simple and inexpensive procedure is proposed for the extension of the dynamic range of flame atomic absorption spectrometry measurements using on-line dilution. The proposed methodology is based on the use of a manifold with two coupled dilution chambers and a zone injection system. The samples are prediluted in a closed system which includes a variable-volume mixing chamber (10–120 ml) and two injection valves. The samples are injected through one of these valves, and the other is employed to take 100 μl of prediluted samples which are then passed through a new dilution chamber (volume 1–10 ml) and aspirated by the nebulizer of the instrument. A third injection valve mounted in the last part of the manifold is used for the direct injection of diluted standard solutions. Various dilution factors are obtained, ranging from 2 to 130 000 times, thus extending the analytical range of copper determination to more than 100 000 mg l⁻¹.     

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.