Comparison of in-tube sorptive extraction techniques for non-polar volatile organic compounds by gas chromatography with mass spectrometric detection

A commercial in-tube sorptive extraction device, known as solid-phase dynamic extraction (SPDE), has been evaluated for the extraction of non-polar volatile aromatic analytes from aqueous solutions in both headspace and liquid injection modes. An automated sampler is used with a gas-tight 2.5 ml syringe equipped with a special needle that is coated on the inside with a non-polar extraction phase. After absorption onto the phase, the analytes were thermally desorbed directly into a GC-MS system. The technique was evaluated for the determination of furan, benzene and toluene. The sensitivity for toluene was greatly improved on using SPDE compared to static headspace. A slight increase in sensitivity was observed for benzene but none for determination of furan. Estimated limits of detection ranged from 0.2 to 2 microg/l.     

Automated headspace solid-phase dynamic extraction to analyse the volatile fraction of food matrices

High concentration capacity headspace techniques (headspace solid-phase microextraction (HS-SPME) and headspace sorptive extraction (HSSE)) are a bridge between static and dynamic headspace, since they give high concentration factors as does dynamic headspace (D-HS), and are as easy to apply and as reproducible as static headspace (S-HS). In 2000, Chromtech (Idstein, Germany) introduced an inside-needle technique for vapour and liquid sampling, solid-phase dynamic extraction (SPDE), also known as "the magic needle". In SPDE, analytes are concentrated on a 50 microm film of polydimethylsiloxane (PDMS) and activated carbon (10%) coated onto the inside wall of the stainless steel needle (5 cm) of a 2.5 ml gas tight syringe. When SPDE is used for headspace sampling (HS-SPDE), a fixed volume of the headspace of the sample under investigation is sucked up an appropriate number of times with the gas tight syringe and an analyte amount suitable for a reliable GC or GC-MS analysis accumulates in the polymer coating the needle wall. This article describes the preliminary results of both a study on the optimisation of sampling parameters conditioning HS-SPDE recovery, through the analysis of a standard mixture of highly volatile compounds (beta-pinene, isoamyl acetate and linalool) and of the HS-SPDE-GC-MS analyses of aromatic plants and food matrices. This study shows that HS-SPDE is a successful technique for HS-sampling with high concentration capability, good repeatability and intermediate precision, also when it is compared to HS-SPME.     

Use of in-tube sorptive extraction techniques for determination of benzene, toluene, ethylbenzene and xylenes in soft drinks

A comparison is made between static headspace analysis and headspace solid-phase dynamic extraction (HS-SPDE) for the quantitative determination of trace level BTEX solvents (benzene, toluene, ethylbenzene and o-, m-, and p-xylene) in soft drinks. Two non-polar extraction phases were investigated for SPDE using an automated sampler with a gas-tight syringe equipped with a special needle coated on the inside with the extraction phase. Following adsorption onto the phase, the analytes were thermally desorbed directly into a GC-MS. The techniques were optimised and evaluated by analysis of spiked soft drink samples. The use of the SPDE device gave comparable results to the static headspace method, with lower detection limits for some compounds, and also offers advantages for applications where lower temperatures are preferred.     

Accelerated solid-phase dynamic extraction for the analysis of biogenic volatile organic compounds in air

In this study, accelerated solid phase dynamic extraction (ASPDE) technique was used to identify biogenic volatile organic compounds (BVOCs) emitted from Norway spruce (Picea abies). Compounds that were determined in tree samples are: tricycylene, α-pinene, camphene, β-pinene, myrcene, 3-carene, p-cymene, limonene, cineole, α-phellandrene, α-terpinene, γ-terpinene and terpinolene. ASPDE showed a potential for the analysis of environmental samples as well as for field applications. This technique was further studied by using a gaseous mixture of BVOCs (sabinene, α-pinene, β-pinene, limonene, linalool, and (Z)-hexenyl acetate) and exhibited a good repeatability during all the experiments in the range of 2.5% (α-pinene) and 14.6% (linalool). However, during the analysis of samples it was observed that desorption at high temperature (230°C) can lead to the formation of artifacts, which were not observed at the desorption temperature of 100°C. Further experimental investigations revealed that monoterpenes appeared as unanticipated compounds during desorption of ASPDE samples; these compounds were degradation products of linalool.     

Influence of different extraction parameters on a solid-phase dynamic extraction for the gas chromatographic determination of d-limonene degradation products by using a fractional factorial design

Through the application of a solid-phase dynamic extraction (SPDE) method for the determination of volatile substances, different parameters may influence the extraction and desorption process and are, therefore, vital for the determination of the extracted substances via gas chromatography (GC). In this study, the influence of extraction und desorption parameters of an SPDE-GC method for the determination of the d-limonene degradation products, namely, alpha-terpineol, (-)-carveol, and (S)-carvone, in an aqueous model system was evaluated using a factorial fractional design. The aim was to reduce the number of factors that should be considered for the optimization of an SPDE procedure for different applications. It could be shown that the extraction efficiency of alpha-terpineol, (-)-carveol, and (S)-carvone is significantly influenced by the extraction parameters incubation temperature, number of extraction strokes, and amount of added NaCl. All 3 parameters have a positive effect on the extraction and determination of the examined d-limonene degradation products. Due to the identification of significant factors on the basis of an experimental design, the results of this study can be very useful for further development of SPDE methods for different applications.     

Sol-gel titania-coated needles for solid phase dynamic extraction-GC/MS analysis of desomorphine and desocodeine

Novel sol-gel titania film coated needles for solid-phase dynamic extraction (SPDE)-GC/MS analysis of desomorphine and desocodeine are described. The high thermal stability of titania film permits efficient extraction and analysis of poorly volatile opiate drugs. The influences of sol-gel reaction time, coating layer, extraction and desorption time and temperature on the SPDE needle performance were investigated. The deuterium labeled internal standard was introduced either during the extraction of analyte or directly injected to GC after the extraction process. The latter method was shown to be more sensitive for the analysis of water and urine samples containing opiate drugs. The proposed conditions provided a wide linear range (from 5-5000 ppb), and satisfactory linearity, with R(2) values from 0.9958 to 0.9999, and prominent sensitivity, LOQs (1.0-5.0 ng/g). The sol-gel titania film coated needle with SPDE-GC/MS will be a promising technique for desomorphine and desocodeine analysis in urine.     

Analysis of benzene, toluene, ethylbenzene, xylenes and n-aldehydes in melted snow water via solid-phase dynamic extraction combined with gas chromatography/mass spectrometry

The present study describes a method based on headspace-solid-phase dynamic extraction (HS-SPDE) followed by GC/MS for the qualitative and quantitative analysis of benzene, toluene, ethylbenzene, o-, m- and p-xylene (BTEX), and n-aldehydes (C(6)-C(10)) in water. To enhance the extraction capability of the HS-SPDE a new cooling device was tested that controls the temperature of the SPDE needle during extraction. Extraction and desorption parameters such as the number of extraction cycles, extraction temperature, desorption volume and desorption flow rate have been optimized. Detection limits for BTEX ranged from 19 ng/L (benzene) to 30 ng/L (m/p-xylene), while those for n-aldehydes ranged from 21 ng/L (n-heptanal) to 63 ng/L (n-hexanal). At a concentration level of 2 microg/L, the relative standard deviations (RSDs) for BTEX ranged from 3.9% (benzene) to 15.3% (ethylbenzene), while RSDs for n-aldehydes were between 6.1% (n-octanal) and 16.5% (n-hexanal) (n=7). Best results were obtained when the analyzed water samples were heated to 50 degrees C. At a water temperature of 70 degrees C GC responses decreased for all analyzed compounds. At a defined water temperature, a significant improvement of the GC response was achieved by cooling of the SPDE fiber during water extraction in comparison to an extraction keeping the fiber at room temperature. Evaluating the extraction cycles, for BTEX, the sensitivity was almost similar using 20, 40 and 60 extraction cycles. In contrast, the highest GC responses for n-aldehydes were achieved by the use of 60 extraction cycles. Optimizing the desorption parameters, best results were achieved using the smallest technical available desorption volume of 500 microL and the highest technical desorption flow rate of 50 microL/s. The method was applied to the analysis of melted snow samples taken from the Jungfraujoch, Switzerland (3580 m asl), revealing the presence of BTEX and aldehydes in snow.     

Optimization of Modern Analytical SPME and SPDE Methods for Determination of <Emphasis Type="Italic">Trans</Emphasis>-2-nonenal in Barley,Malt and Beer

Trans-2-nonenal is an aldehyde contributing to an unpleasant off-flavor and odor of rancid butter in stored beer. The automated solid-phase microextraction technique (SPME) coupled with gas chromatography (GC) and solid-phase dynamic extraction (SPDE) coupled with gas chromatography were optimized and introduced to determine trans-2-nonenal in barley, malt and beer. Five types of SPME fibers coated with different stationary phases (100 μm PDMS, 65 μm PDMS/DVB, 85 μm CAR/PDMS, 50/30 μm DVB/CAR/PDMS, 85 μm PA) and two needles (PDMS, PDMS/AC) were compared and tested for their efficiencies in the headspace (HS) SPME and SPDE determination of trans-2-nonenal in barley, malt and beer. The highest extraction efficiency of HS-SPME was achieved with the PDMS/DVB fiber, and addition of 1.5 g of NaCl, extraction time was 20 min at 60 °C. The highest extraction efficiency of HS-SPDE was obtained with the PDMS needle, 15 extraction strokes at 60 °C and addition of 1.5 g of NaCl. Trans-2-nonenal was identified with the method of HS-SPME coupled gas chromatography-mass spectrometry (GC–MS); the samples were analyzed using the HS-SPME-GC-coupled gas chromatography-flame ionization detector (GC-FID) technique.     

Determination of volatile organic hydrocarbons in water samples by solid-phase dynamic extraction

In the present study a headspace solid-phase dynamic extraction method coupled to gas chromatography–mass spectrometry (HS-SPDE-GC/MS) for the trace determination of volatile halogenated hydrocarbons and benzene from groundwater samples was developed and evaluated. As target compounds, benzene as well as 11 chlorinated and brominated hydrocarbons (vinyl chloride, dichloromethane, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, carbon tetrachloride, chloroform, trichloroethylene, tetrachloroethylene, bromoform) of environmental and toxicological concern were included in this study. The analytes were extracted using a SPDE needle device, coated with a poly(dimethylsiloxane) with 10% embedded activated carbon phase (50-μm film thickness and 56-mm film length) and were analyzed by GC/MS in full-scan mode. Parameters that affect the extraction yield such as extraction and desorption temperature, salting-out, extraction and desorption flow rate, extraction volume and desorption volume, the number of extraction cycles, and the pre-desorption time have been evaluated and optimized. The linearity of the HS-SPDE-GC/MS method was established over several orders of magnitude. Method detection limits (MDLs) for the compounds investigated ranged between 12 ng/L for cis-dichloroethylene and trans-dichloroethylene and 870 ng/L for vinyl chloride. The method was thoroughly validated, and the precision at two concentration levels (0.1 mg/L and a concentration 5 times above the MDL) was between 3.1 and 16% for the analytes investigated. SPDE provides high sensitivity, short sample preparation and extraction times and a high sample throughput because of full automation. Finally, the applicability to real environmental samples is shown exemplarily for various groundwater samples from a former waste-oil recycling facility. Groundwater from the site showed a complex contamination with chlorinated volatile organic compounds and aromatic hydrocarbons. Figure SPDE Principle     

固相萃取采样和气相色谱-质谱检测液化石油气中的芳烃杂质（英文）

建立石墨化碳(GCB)为吸附剂的动态采样系统,可实现液化石油气(LPG)中芳烃杂质的采样和同步萃取富集。LPG中的芳烃杂质(苯、甲苯、二甲苯、苯乙烯和萘)被快速捕集后,进行气相色谱-质谱(GC-MS)定性定量分析。与C18和苯乙烯二乙烯苯吸附剂(PS-DVB)相比,GCB填充柱对芳烃杂质的萃取效率最高。评价了基于GCB填充柱采样的吸附效率、重现性和贮存稳定性。采样和分析方法对氮气模拟气流中8种芳烃的定量分析线性范围为15~1 000μg/m~3。所开发的方法具有回收率高(92.9%~109.0%)、检出限低(1.0~6.2μg/m~3)、准确性好(相对标准偏差为0.6%~5.8%)和准确度高(标准偏差为0.8%~8.2%)等优点。     

Solid-phase dynamic extraction for the enrichment of polar volatile organic compounds from water

Headspace solid-phase dynamic extraction coupled to gas chromatography-mass spectrometry (HS-SPDE-GC/MS) was evaluated for the trace determination of polar volatile organic compounds (PVOC) from aqueous matrices. The target compounds included 3 ethers and 12 alcohols. Four SPDE needle coatings with different phase polarities and sorption properties (WAX, 1701, PDMS, PDMS/AC) were tested. The effects of extraction temperature, number of extraction cycles, and ionic strength on partitioning of the target compounds have been investigated in detail, including the determination of salting-out constants for the investigated compounds. Lowest method detection limits (MDLs) were obtained with the WAX and the PDMS/AC phase. The WAX phase showed MDLs for ethers in the range of 0.06 microg/L (MTBE) to 0.8 microg/L (1,4-dioxane) and for alcohols between 0.02 microg/L (3-methyl-1-pentanol) and 3.5 microg/L (1-propanol). The evaluated MDLs for ethers with the PDMS/AC were in the range 0.06 microg/L (MTBE) to 1.2 microg/L (1,4-dioxane) and for alcohols between 0.004 microg/L (1-hexanol) and 4.9 microg/L (ethanol). Using either of these two phases, SPDE provides comparable or better sensitivities for the investigated compounds than other enrichment techniques, high sample throughput because of full automation, and short extraction times as well as a high robustness of the extraction phase because of its protection inside the steel needle. SPDE applicability has been demonstrated for the determination of fusel oils in different alcoholic beverages.     

Validation of methods for measuring polychlorinated dibenzo- p -dioxins and furans,and dioxin-like polychlorinated biphenyls in flue gas

Method validation was performed on the collection and extraction procedures for an analysis of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DLPCBs) in flue gas. The adoption of the rapid pressurized liquid extraction (PLE) technique was evaluated for extraction from polyurethane foam plugs (PUFPs) and fly ash. With respect to extraction from PUFPs, dichloromethane PLE showed an extraction efficiency equivalent to that of conventional acetone Soxhlet, while toluene PLE was found to have a lower extraction efficiency from fly ash than toluene Soxhlet. The collection ability of three sampling methods, employed in the Japanese standard analytical method JIS K0311 (revised in 2005) was evaluated by evaluating the distribution of gaseous PCDD/Fs and DLPCBs in each collection compartment in sampling trains. A DiOANA® fibrous alumina filter and a PUFP, newly employed trapping devices in the revised JIS method, were found to trap gaseous analytes effectively. The validation of the two newly employed sampling methods (DiOANA and PUFP) was tested by parallel measurements of the methods with a conventional five-impinger method, and good agreements on the PCDD/Fs and DLPCBs quantities were demonstrated.     

Application of tandem mass spectrometry combined with gas chromatography and headspace solid-phase dynamic extraction for the determination of drugs of abuse in hair samples

A new method combination, headspace solid-phase dynamic extraction coupled with gas chromatography/tandem mass spectrometry (HS-SPDE/GC/MS/MS), is introduced to determine drugs of abuse in hair samples. This highly automated procedure utilizes SPDE for pre-concentration and on-coating derivatization as well as GC and triple quadrupole MS/MS for selective and sensitive detection. All these steps, apart from washing and cutting of the hair samples, are performed without manual intervention on a robot-like autosampler.SPDE is a solventless extraction technique related to solid-phase microextraction (SPME). The analytes are absorbed from the sample headspace directly into a hollow needle with an internal coating of polydimethylsiloxane by repeated aspirate/dispense cycles.The HS-SPDE/GC/MS/MS procedure was applied to the analysis of methadone, the trimethylsilyl derivatives of cannabinoids and the trifluoroacetyl derivatives of amphetamines and designer drugs. The method was shown to be sensitive with detection limits between 6 and 52 pg/mg hair matrix and precision between 0.4 and 7.8% by the use of an internal standard technique. Linearity was obtained from 0.1-20 ng/mg with coefficients of correlation between 0.995 and 0.999.Compared with conventional methods of hair analysis, HS-SPDE/GC/MS/MS is easier to use, substantially faster, with the degree of sensitivity and reproducibility demanded in clinical and forensic toxicology. The main advantage of the SPDE technique in relation to SPME is the robustness of the capillary.     

Simultaneous determination of 15 steroidal oral contraceptives in water using solid-phase disk extraction followed by high performance liquid chromatography–tandem mass spectrometry

A rapid, accurate and sensitive method for simultaneous determination of 15 steroidal hormones including four estrogens (estrone, 17β-estradiol, 17α-ethynylestradiol, estriol) and eleven progestogens (17β-estradiol-3-benzoate, 19-norethindrone, gestodene, levonorgestrel, medroxyprogesterone, cyproterone acetate, megestrol-17-acetate, progesterone, norethindrone acetate, chlormadinone-17-acetate, and hydroxy progesterone caproate) in environmental waters was developed by coupling solid-phase disk extraction (SPDE) to ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) with electrospray ionization. Among three types of extraction tested (C₈ SPDE, C₁₈ SPDE and C₁₈ SPE), the most satisfactory result was achieved using C₁₈ SPDE for its satisfactory recovery (75.6 to 101.4%) and short extraction time (15 min for 1 L deionised water). The validity of this method was investigated and good analytical performance for all the analytes was obtained, including low limits of method detection (0.5–3.4 ng/L) and excellent linear dynamic range (1.0–50.0 ng/L). The method was applied to determine the steroidal hormones in 10 environmental waters including tap water, river water, lake water and waste water in Beijing. No progestogen was detected in all samples and estrone, estriol, 17α-ethynylestradiol were found in most samples at levels between 1.8 and 127.9 ng/L.     

The active and passive sampling of benzene, toluene, ethyl benzene and xylenes compounds using the inside needle capillary adsorption trap device

A new and simple method of solventless extraction of volatile organic compounds (VOCs) from air is presented. The sampling device has an adsorbing carbon coating on the interior surface of a hollow needle, and is called the inside needle capillary adsorption trap (INCAT). This paper describes a study of the reproducibility in the preparation and sampling of the INCAT device. In addition, this paper examines the effects of sample volume in active sampling and exposure time in passive sampling on the analyte adsorption. Analysis was achieved by sampling the air from an environmental chamber doped with benzene, toluene, ethyl benzene and xylenes (BTEX) compounds. Initial rates of adsorption were found to vary among the different compounds, but ranged from 0.0099 to 0.016 nmol h(-1) for passive sampling and from 2.2 to 10 nmol h(-1) for active sampling. Analysis was done by thermal desorption of the adsorbed compounds directly into a gas chromatograph injection port. Quantification of the analysis was done by comparison to actively sampled activated carbon solid phase extraction (SPE) measurements.     

An assessment of the liquid–gas partitioning behavior of major wastewater odorants using two comparative experimental approaches: liquid sample-based vaporization vs. impinger-based dynamic headspace extraction into sorbent tubes

The gas–liquid partitioning behavior of major odorants (acetic acid, propionic acid, isobutyric acid, n-butyric acid, i-valeric acid, n-valeric acid, hexanoic acid, phenol, p-cresol, indole, skatole, and toluene (as a reference)) commonly found in microbially digested wastewaters was investigated by two experimental approaches. Firstly, a simple vaporization method was applied to measure the target odorants dissolved in liquid samples with the aid of sorbent tube/thermal desorption/gas chromatography/mass spectrometry. As an alternative method, an impinger-based dynamic headspace sampling method was also explored to measure the partitioning of target odorants between the gas and liquid phases with the same detection system. The relative extraction efficiency (in percent) of the odorants by dynamic headspace sampling was estimated against the calibration results derived by the vaporization method. Finally, the concentrations of the major odorants in real digested wastewater samples were also analyzed using both analytical approaches. Through a parallel application of the two experimental methods, we intended to develop an experimental approach to be able to assess the liquid-to-gas phase partitioning behavior of major odorants in a complex wastewater system. The relative sensitivity of the two methods expressed in terms of response factor ratios (RF_vap/RF_imp) of liquid standard calibration between vaporization and impinger-based calibrations varied widely from 981 (skatole) to 6,022 (acetic acid). Comparison of this relative sensitivity thus highlights the rather low extraction efficiency of the highly soluble and more acidic odorants from wastewater samples in dynamic headspace sampling.     

Application of headspace solvent microextraction to the analysis of mononitrotoluenes in waste water samples

The possibility of applying headspace solvent microextraction (HSME) for determination of mononitrotoluenes (MNTs) in waste water samples is demonstrated. A drop of n-amyl alcohol containing naphthalene as an internal standard was suspended from the tip of a microsyringe needle over the headspace of stirred sample solutions for a predescribed extraction period. The drop was then injected directly into a gas chromatograph. Optimization of experimental parameters such as the nature of extracting solvent, microdrop and sample volumes, sampling temperature, stirring rate, ionic strength of the solution, pH and extraction time on HSME efficiency were investigated. Then enrichment factor, dynamic linear range (DLR), limit of detection (LOD) and precision of the method were evaluated by water samples spiked with MNTs. Finally, the method was successfully applied to the extraction and determination of the mononitrotoluenes in waste waters of both P.C.I. Company and Research Center of Azad University.     

Coupling of Dynamic Headspace Sampling and Solid Phase Microextraction

A simple lab-made apparatus allowing the use of a SPME fiber as sorptive device for isolation of analytes from varied samples using dynamic headspace sampling (DHS) is presented here. The principal parameters for the operation of this device - the extraction time and the flow of purging gas - were studied using aqueous test solutions of volatile and semi-volatile analytes. Compared to conventional HS-SPME, DHS-SPME provided a substantial reduction in the extraction time with linearity, accuracy and precision comparable to the conventional approach. For a complex matrix such as mango pulp, the extraction efficiency of volatiles using the DHS-SPME combination was up to six times higher than that of conventional HS-SPME.     

Trace analysis of BTEX compounds in water with a membrane interfaced ion mobility spectrometer

A tubular silicone membrane interface has been developed for trace detection of benzene, toluene, ethyl benzene, and xylene (BTEX) compounds in water with a portable ion mobility spectrometer. Effects of flow rate, membrane length and stirring conditions on the IMS signals have been systematically investigated. Besides conventional dynamic mode operation, static mode sampling has been demonstrated for the first time and high sensitivities were achieved by sampling of BTEX contaminated water with static mode operation. A toluene concentration of 0.101 mg l(-1) in purified water, corresponding to a headspace concentration of 2.75 (mug m(-3)), was determined by static mode sampling. Headspace sampling without the membrane interface could not detect toluene at this concentration. This method has high sensitivity for trace concentrations of gasoline components in river water with a response time of several seconds. The apparatus developed is portable and can be used for sensitive detection of organic contaminants in water, with improved performance compared to conventional modes of IMS sampling.     

Gas chromatographic-mass spectrometric determination of sulfolane in wetland vegetation exposed to sour gas-contaminated groundwater

Described is a GC-MS method for the determination of the levels of sulfolane (tetrahydrothiophene 1,1-dioxide, C4H8O2S; a water miscible chemical used in the sweetening of sour gas) in wetland vegetation (roots, shoots, berries, seeds, grasses, and leaves). The technique was developed to provide positive detection of sulfolane in a variety of wetland vegetation and to determine the extent to which sulfolane may translocate within the plants. Vegetation samples collected at a sour gas processing facility were extracted using a two-stage process which utilized a back extraction of a water extract with toluene. The main advantages of this procedure were: good extraction efficiency (recovery of 80+/-12%), exclusion of most of the highly polar co-extractives during the toluene back extraction step, and a final extract well suited to routine GC-MS selected ion monitoring of sulfolane with a detection limit of 90 ng g(-1) (wet mass). In general, the method was rugged, based on a study period of 18 months in which over 175 runs were conducted.