Quantification of transformation products of rocket fuel unsymmetrical dimethylhydrazine in air using solid-phase microextraction

Quantification of unsymmetrical dimethylhydrazine transformation products in ambient air is important for assessing the environmental impact of heavy rocket launches. There are very little data of such analyses, which is mainly caused by the low number of analytes covered by the available analytical methods and their complexity. A simple and cost-efficient method for accurate simultaneous determination of seven unsymmetrical dimethylhydrazine transformation products in air using solid-phase microextraction followed by gas chromatography-mass spectrometry was developed. The method was optimized for air sampling and solid-phase microextraction from 20-mL vials, which allows full automation of analysis. The extraction for 5 min by Carboxen/polydimethylsiloxane fiber from amber vials and desorption for 3 min provided the greatest analytes' responses, lowest relative standard deviations, linear calibration (R² ≥ 0.99), and limits of detection from 0.12 to 0.5 μg/m³. Samples with concentrations 500 μg/m³ can be stored at 21 ± 1°C without substantial losses (1–11%) for up to 24 h, while air samples with concentrations 10 and 50 μg/m³ stored for up to 24 h can be used for accurate quantification of only two and four out of seven analytes, respectively. The developed method was successfully tested for the analysis of air above real soil samples contaminated with unsymmetrical dimethylhydrazine rocket fuel.     

Determination of the products of the transformation of unsymmetrical dimethylhydrazine in soils using chromatography/mass spectrometry

An approach is proposed for the simultaneous determination of formic acid N,N-dimethylhydrazide and 1-methyl-1-H-1,2,4-triazole (ecotoxicants formed upon the oxidative transformation of unsymmetrical dimethylhydrazine) in soils in the concentration range 0.05–50 mg/kg using gas chromatography/mass spectrometry. The conditions for the quantitative extraction of the components by continuous periodic extraction with methanol have been found. The adsorption of formic acid N,N-dimethylhydrazide and 1-methyl-1-H-1,2,4-triazole from solutions by soils of different types has been studied and a method has been proposed for preparing uniform model soil samples with the required contaminant concentrations.     

Potential sources of background contaminants in solid phase extraction and microextraction

A study to identify the sources of background contamination from SPE, using a C-18 sorbent, and solid-phase microextraction (SPME), using a 70 microm carbowax/divinylbenzene (CW/DVB) fiber, was carried out. To determine the source of contamination, each material used in the procedure was isolated and examined for their contribution. The solid-phase column components examined were: sorbent material and frits, column housings and each solvent used to elute analytes off the column. The components examined in the SPME procedure were: SPME fiber, SPME vials, water (HPLC grade), and salt (sodium chloride) used to increase the ionic strength. The majority of the background contaminants from SPE were found to be from the SPE sorbent material and frits. The class of contaminants extracted during a blank extraction were phthalates and other plasticizers used during the manufacturing process. All had blank levels corresponding to measured concentrations below 2 ng/ mL, except for undecane, which had a concentration of 5.4 ng/mL. The most prevalent contaminants in the SPME blank procedure are 1,9-nonanediol, a mixture of phthalates and highly bis-substituted phenols. All the concentrations were below 2 ng/mL, with the exception of bis (2-ethylhexyl) phthalate, which had concentrations ranging from 5 to 20 ng/mL.     

Determination of the fungicides vinclozolin and dicloran in soils using ultrasonic extraction coupled with solid-phase microextraction

Solid-phase microextraction (SPME) coupled to ultrasonic extraction was evaluated for extracting trace amounts of two agrochemical fungicides, vinclozolin and dicloran, in soil samples. Extraction was performed following two experimental approaches prior to the submission of the aqueous extracts to SPME-GC analysis. In the first approach, extraction involved sample homogenization with a water solution containing 5% (v/v) acetone and centrifugation prior to fiber extraction. In the second approach, the extraction of the fungicides from the soil samples was conducted using acetone as organic solvent which was then diluted with water to give a 5% (v/v) content. The pesticides were isolated with fused silica fiber coating with 85 μm polyacrylate. Parameters that affect both the extraction of the fungicides by the soil samples and the trapping of the analytes by the fiber were investigated and their impact on the SPME-GC-MS was studied. The procedures with respect to repeatability and limits of detection were evaluated by soil spiked with both analytes. Repeatability was between 5.6 and 14.2% and the limits of detection were 2-13 ng g⁻¹. The efficiency of acetone/SPME was generally better than that for water/SPME procedure showing good linearity (R²>0.99) with coefficient variations below 9%, recoveries higher than 91% and limits of detection between 2 and 3 ng g⁻¹. Finally, the recoveries obtained with acetone/SPME procedure were compared with the conventional liquid-liquid extraction using real soil samples. The acetone/SPME method was shown to be an inexpensive, fast and simple preparation method for the determination of target analytes at low nanogram per gram levels in soils.     

Determination of fatty acids in soil samples by gas chromatography with mass spectrometry coupled with headspace solid‐phase microextraction using a homemade sol–gel fiber†

Through the use of a homemade sol–gel‐derived fiber, a headspace solid‐phase microextraction technique coupled to gas chromatography with mass spectrometry was developed for the determination of fatty acids with long, even‐numbered carbon chains (C₁₂–C₂₄) in soil samples. The experimental parameters such as reaction time, temperature, and ionic strength that might affect derivatization, extraction, and desorption were investigated. Under the optimized conditions, the linearity of the method ranged from 0.1 to 100 mg/L with a correlation coefficient >0.997. The limit of detection values based on a signal‐to‐noise ratio of 3:1 were determined with the concentration from 0.39 to 39.4 μg/L. The recoveries of the method for the soil samples were from 91.15 to 108.1%. This developed method using a homemade fiber showed a higher sensitivity than that using a commercial polydimethylsiloxane fiber and was also for the analysis of real soil samples from the Paomaling geological park of China.     

顶空固相微萃取-气相色谱-质谱联用分析纺织品中挥发性有机物

建立了顶空固相微萃取（HSSPME）-气相色谱（GC）-质谱（MS）联用测定纺织品中甲苯、4-乙烯基环己烯、苯乙烯、萘和1-苯基环己烯5种挥发性有机物（VOCs）的分析方法。选择聚二甲基硅氧烷（PDMS）作为萃取涂层,优化了SPME的萃取条件,包括平衡时间、萃取时间、萃取温度、顶空体积、离子强度、搅拌速度、解吸温度和时间以及GC—MS仪器条件。对于甲苯、4-乙烯基环己烯、苯乙烯、萘和1-苯基环己烯方法线性范围分别为0．087～870、3．32～3320、2．28～2280、0．015～150和0．050～50．0ng／g;检出限分别为0．005、0．042、0．670、0．008和0．011ng／g。实际样品加标回收率在80．1％～122％之间,RSD在0．8％～8．6％之间。方法符合纺织品中痕量VOCs的快速分析要求。     

Determination of benzene, toluene, ethylbenzene and xylenes in soils by multiple headspace solid-phase microextraction

Multiple headspace-solid phase microextraction (MHS-SPME) is a recently developed technique for the quantification of analytes in solid samples that avoids the matrix effect. This method implies several consecutive extractions from the same sample. In this way, the total area corresponding to complete extraction can be directly calculated as the sum of the areas of each individual extraction when the extraction is exhaustive, or through a mathematical equation when it is not exhaustive. In this paper, the quantitative determination of benzene, toluene, ethylbenzene and xylene isomers (BTEX) in a certified soil (RTC-CRM304, LGC Promochem) and in a contaminated soil by multiple HS-SPME coupled to a gas chromatography-flame ionisation detector (GC-FID) is presented. BTEX extraction was carried out using soil suspensions in water at 30 degrees C with a 75 microm carboxen-polydimethylsiloxane (CAR-PDMS) fibre and calibration was carried out using aqueous BTEX solutions at 30 degrees C for 30 min with the same fibre. BTEX concentration was calculated by interpolating the total peak area found for the soils in the calibration graphs obtained from aqueous solutions. The toluene, ethylbenzene, o-xylene and m,p-xylene concentrations obtained were statistically equal to the certified values.     

Determination of triazines and amides in water using solid phase microextraction coupled with GC-MS

Summary Solid phase microextraction was coupled with gas chromatography-mass spectrometry (SPME-GC-MS) to screen for sixteen nitrogen-containing compounds, including herbicides, in water samples. The effects of stirring, extraction time, pH, salt concentration and the choice of fiber coating material were evaluated. The repeatability was in the range of 0.72–18.2 (CV % at 200 ng·L⁻¹) and the reproducibility, in the range of 5.4–34 (at 500 ng·L⁻¹).     

Development of the HS-SPME-GC-MS/MS method for analysis of chemical warfare agent and their degradation products in environmental samples

After World War II approximately 50,000 tons of chemical weapons were dumped in the Baltic Sea by the Soviet Union under the provisions of the Potsdam Conference on Disarmament. These dumped chemical warfare agents still possess a major threat to the marine environment and to human life. Therefore, continue monitoring of these munitions is essential. In this work, we present the application of new solid phase microextraction fibers in analysis of chemical warfare agents and their degradation products. It can be concluded that the best fiber for analysis of sulfur mustard and its degradation products is butyl acrylate (BA), whereas for analysis of organoarsenic compounds and chloroacetophenone, the best fiber is a co-polymer of methyl acrylate and methyl methacrylate (MA/MMA). In order to achieve the lowest LOD and LOQ the samples should be divided into two subsamples. One of them should be analyzed using a BA fiber, and the second one using a MA/MMA fiber. When the fast analysis is required, the microextraction should be performed by use of a butyl acrylate fiber because the extraction efficiency of organoarsenic compounds for this fiber is acceptable. Next, we have elaborated of the HS-SPME-GC-MS/MS method for analysis of CWA degradation products in environmental samples using laboratory obtained fibers The analytical method for analysis of organosulfur and organoarsenic compounds was optimized and validated. The LOD's for all target chemicals were between 0.03 and 0.65 ppb. Then, the analytical method developed by us, was used for the analysis of sediment and pore water samples from the Baltic Sea. During these studies, 80 samples were analyzed. It was found that 25 sediments and 5 pore water samples contained CWA degradation products such as 1,4-dithiane, 1,4-oxathiane or triphenylarsine, the latter being a component of arsine oil. The obtained data is evidence that the CWAs present in the Baltic Sea have leaked into the general marine environment.     

Investigation of fragrance stability used in the formulation of cosmetic and hygienic products using headspace solid‐phase microextraction by nanostructured materials followed by gas chromatography with mass spectrometry

A new composite coating of polypyrrole and sodium lauryl ether sulfate was electrochemically prepared on a stainless‐steel wire using cyclic voltammetry. The application and performance of the fiber was evaluated for the headspace solid‐phase microextraction of a fragrance in aqueous bleach samples followed by gas chromatography combined with mass spectrometry to assess the fragrance stability in this kind of household cleaning product. To obtain a stable and efficient composite coating, parameters related to the coating process such as scan rate and numbers of cycles were optimized using a central composite design. In addition, the effects of various parameters on the extraction efficiency of the headspace solid‐phase microextraction process such as extraction temperature and time, ionic strength, sample volume, and stirring rate were investigated by experimental design methods using Plackett–Burman and Doehlert designs. The optimum values of 53°C and 28 min for sample temperature and time, respectively, were found through response surface methodology. Results show that the combination of polypyrrole and sodium lauryl ether sulfate in a composite form presents desirable opportunities to produce new materials to study fragrance stability by headspace solid‐phase microextraction.     

Fundamentals and applications of needle trap devices: A critical review

The needle trap device (NTD) is an extraction trap that contains a sorbent inside a small needle, through which fluid can be actively drawn into and out of by a gas-tight syringe or pump, or analytes can be introduced passively to the trap by diffusion. The needle trap (NT) is a potentially solventless sampling technique/sample preparation and introduction device. Both fluid-borne analytes and particles can be trapped inside the needle and then adsorbed analytes are desorbed in an inlet of analytical instrument and introduced for identification and quantification. The fluid may be either gaseous or liquid. The objectives of this critical review are to summarize the theory of the sampling process for both active and passive time-average extraction modes in addition to outlining the evolution of the technology and main applications.     

The determination of volatile organic compounds in soils using solid phase microextraction with gas chromatography-mass spectrometry

Solid phase microextraction (SPME) was applied in the development of a protocol for the analysis of a number of target organic compounds in landfill site samples. The selected analytes, including aromatic hydrocarbons, chlorinated hydrocarbous, and unsaturated compounds, were absorbed directly from a headspace sample above a soil layer onto a fused silica fiber. Following exposure, the fiber was thermally desorbed in the injection port of the gas chromatograph and eluted compounds were detected using a mass selective detector. The stability and sensitivity of the extraction technique were examined at five temperatures (22–60°C) using a 100μm polydimethylsiloxane fiber. Calibrations, using soil samples spiked with selected solvents (0.5–30 μg/g), were linear; trichloroethene (r² = 0.992) and benzene (r² = 0.998). SPME was applied to the examination of a municipal landfill where 8 sites were sampled, at three depths, resulting in the detection of xylene (maximum 2.8 μg/g) and a number of other non-target organic contaminants.     

Characterisation of absorptive sampling with SPME fibres in the EUPHORE photoreactor

The implementation of an experimental set-up for sampling, and characterisation of parameters related to absorptive sampling solid phase microextraction (SPME) in the EUPHORE photoreactor is described. Toluene was taken as probe compound. Optimisation of the sampling and calibration curves are presented. Equilibrium was achieved in just 30 s due to the good agitation in the chambers and the LOD was 0.24 ppbV. The precision was ±0.02 expressed as relative standard deviation (n = 9). The inter-fibre reproducibility was ±0.03 expressed as relative standard deviation. The effect of the temperature and the sun radiation on absorption in the fibre is also studied using a relative method to calculate the ratio K/K₀ (ratio of absorption constants at two different times during the experiment at which temperature and radiation conditions experimented important variations) calculated through known parameters, avoiding in this way the need for external calibrations in the calculation of K. The results showed a difficult to predict dependence of absorption over the combination of temperature and sun radiation and the need to develop sampling systems with absorptive SPME in which sun radiation has no influence. The stability in different conditions of compounds absorbed in the fibre was also subject to study. At room temperature half of the compound absorbed is expected to desorb in 1.21 h. Conversely, when fibres were kept at low temperatures (−86 °C) after 21 days, desorption was negligible.     

Vacuum-assisted headspace solid phase microextraction of polycyclic aromatic hydrocarbons in solid samples

For the first time, Vacuum Assisted Headspace Solid Phase Microextraction (Vac-HSSPME) is used for the recovery of polycyclic aromatic hydrocarbons (PAHs) from solid matrices. The procedure was investigated both theoretically and experimentally. According to the theory, reducing the total pressure increases the vapor flux of chemicals at the soil surface, and hence improves HSSPME extraction kinetics. Vac-HSSPME sampling could be further enhanced by adding water as a modifier and creating a slurry mixture. For these soil-water mixtures, reduced pressure conditions may increase the volatilization rates of compounds with a low K_H present in the aqueous phase of the slurry mixture and result in a faster HSSPME extraction process. Nevertheless, analyte desorption from soil to water may become a rate-limiting step when significant depletion of the aqueous analyte concentration takes place during Vac-HSSPME. Sand samples spiked with PAHs were used as simple solid matrices and the effect of different experimental parameters was investigated (extraction temperature, modifiers and extraction time). Vac-HSSPME sampling of dry spiked sand samples provided the first experimental evidence of the positive combined effect of reduced pressure and temperature on HSSPME. Although adding 2 mL of water as a modifier improved Vac-HSSPME, humidity decreased the amount of naphthalene extracted at equilibrium as well as impaired extraction of all analytes at elevated sampling temperatures. Within short HSSPME sampling times and under mild sampling temperatures, Vac-HSSPME yielded linear calibration curves in the range of 1–400 ng g⁻¹ and, with the exception of fluorene, regression coefficients were found higher than 0.99. The limits of detection for spiked sand samples ranged from 0.003 to 0.233 ng g⁻¹ and repeatability from 4.3 to 10 %. Finally, the amount of PAHs extracted from spiked soil samples was smaller compared to spiked sand samples, confirming that soil could bind target analytes more strongly and thus decrease the readily available fraction of target analytes.     

Evaluation of a completely automated cold fiber device using compounds with varying volatility and polarity

A fully automated cold fiber solid phase microextraction device has been developed by coupling to a GERSTEL multipurpose (MPS 2) autosampler and applied to the analysis of volatiles and semi-volatiles in aqueous and solid matrices. The proposed device was thoroughly evaluated for its extraction performance, robustness, reproducibility and reliability by gas chromatograph/mass spectrometer (GC/MS). With the use of a septumless head injector, the entire automated setup was capable of analyzing over 200 samples without any GC injector leakages. Evaluation of the automated cold fiber device was carried out using a group of compounds characterized by different volatilities and polarities. Extraction efficiency as well as analytical figures of merit was compared to commercial solid phase microextraction fibers. The automated cold fiber device showed significantly improved extraction efficiency compared to the commercial polydimethylsiloxane (PDMS) and cold fiber without cooling for the analysis of aqueous standard samples due to the low temperature of the coating. Comparing results obtained from cold fiber and commercial divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber temperature profile demonstrated that the temperature gap between the sample matrix and the coating improved the distribution coefficient and therefore the extraction amount. The linear dynamic range of the cold fiber device was 0.5 ng mL⁻¹ to 100 ng mL⁻¹ with a linear regression coefficient ≥0.9963 for all compounds. The limit of detection for all analytes ranged from 1.0 ng mL⁻¹ to 9.4 ng mL⁻¹. The newly automated cold fiber device presents a platform for headspace analysis of volatiles and semi-volatiles for large number of samples with improved throughput and sensitivity.     

Solid‐phase extraction combined with dispersive liquid–liquid microextraction for the determination of pyrethroid pesticides in wheat and maize samples

A rapid, selective and sensitive sample preparation method based on solid‐phase extraction combined with the dispersive liquid–liquid microextration was developed for the determination of pyrethroid pesticides in wheat and maize samples. Initially, the samples were extracted with acetonitrile and water solution followed phase separation with the salt addition. The following sample preparation involves a solid‐phase extraction and dispersive liquid–liquid microextraction step, which effectively provide cleanup and enrichment effects. The main experimental factors affecting the performance both of solid‐phase extraction and dispersive liquid–liquid microextration were investigated. The validation results indicated the suitability of the proposed method for routine analyze of pyrethroid pesticides in wheat and maize samples. The fortified recoveries at three levels ranged between 76.4 and 109.8% with relative standard deviations of less than 10.7%. The limit of quantification of the proposed method was below 0.0125 mg/kg for the pyrethoroid pesticides. The proposed method was successfully used for the rapid determination of pyrethroid residues in real wheat and maize samples from crop field in Beijing, China.     

Improvement of solid phase microextraction fiber assembly and interface for liquid chromatography

Modifications were made on commercial SPME fiber assembly and SPME–LC interface to improve the applicability of SPME for LC. Polyacrylonitrile (PAN)/C18 bonded fuse silica was used as the fiber coating for LC applications because the fiber coating was not swollen in common LC solvents at room temperature. The inner tubing of SPME fiber assembly was replaced with a 457 μm outside diameter (o.d.) solid nitinol rod. And the coated fiber (o.d. 290 μm) was installed onto the nitinol rod. The inner diameter (i.d.) of the through hole of the ferrule in the SPME–LC interface was enlarged to 508 μm to accommodate the nitinol rod. The much larger inner rod protected the fiber coating from being stripped when the fiber was withdrawn from the SPME–LC interface. The system was evaluated in term of pressure test, desorption optimization, peak shape, carryovers, linear range, precision, and limit of detection (LOD) with polycyclic aromatic hydrocarbons (PAHs) as the test analytes. The results demonstrated that the improved system was robust and reliable. It overcame the drawbacks, such as leak of solvents and damage of fiber coatings, associated with current SPME fibers and SPME–LC interface. Another sealing mechanism was proposed by sealing the nitinol rod with a specially designed poly(ether ether ketone) (PEEK) fitting. The device was fabricated and tested for manual use.     

顶空-固相微萃取-气相色谱-质谱法测定烟气中挥发性和半挥发性成分

提出了顶空-固相微萃取-气相色谱-质谱法测定烟气中挥发性和半挥发性成分。结合信息量最大的原则,确定了固相微萃取时萃取纤维头为碳分子筛/聚二甲基硅烷萃取纤维头,萃取温度为70℃,萃取时间为60min。在气相色谱分离中用Agilent DB-1色谱柱为固定相,在质谱分析中采用全扫描模式。结果表明:共鉴定出107种成分,含量最大的成分是烟碱(18.07%),其次是新植二烯(11.46%),主要的3类挥发性和半挥发性成分依次为苯系物、酮类以及杂环类。     

固相微萃取GC-MS快速分析火场残留物中汽油成分

火场残留物如碳灰、烧残物等通常经过样品预处理后进行分析鉴定。传统的样品预处理方法往往操作繁琐、费时、重复性差,而且需用大量有机溶剂,不利于分析人员的身体健康,对环境也会造成一定污染。固相微萃取(solid-phasemicroextraction,SPME)是在固相萃取技术的基础上发展起来的一项新的样品预处理技术,于1989年由加拿大Waterloo大学的J.Pawliszyn教授等首次提出,1993年美国的Supelco公司推出了商业化的固相微萃取设备。该技术具有快速、高效、简便、无需溶剂、易于自动化操作等优点,近年来受到了国外学者的普遍关注,已经被用于环境分析和药品检测等许多领域,