Development of a needle trap device packed with titanium‐based metal‐organic framework sorbent for extraction of phenolic derivatives in air

We developed a novel method of needle trap device packed with titanium‐based metal‐organic framework for the extraction of phenolic derivatives in air followed by gas chromatography‐flame ionization detector analysis. The synthetized adsorbent was packed inside a 22‐gauge spinal needle. This method was first tested at laboratory scale, and then was used for field sampling of phenolic derivatives in air. A glass chamber placed on a heater at 60°C was used to provide different concentrations of phenolic derivatives. The desorption conditions and breakthrough volume were optimized using response surface methodology. The limit of detection and limit of quantitation of the proposed method were estimated to be in the range of 0.001–0.12 and 0.003–0.62 ng/mL, respectively, indicating a high sensitivity for the suggested sampler. Storing the packed needle trap device in a refrigerator at 4?C for 60 days did not dramatically affect the storage stability. Our findings indicated that there was a high correlation coefficient (R² = 0.99) between the measurement results of this method and the NIOSH recommended method (XAD‐7 sorbent tube). Therefore, it can be concluded that the needle trap device packed with titanium‐based metal‐organic framework can be used as a efficient method for extraction of phenolic derivatives in air.     

Sampling and determination of volatile organic compounds with needle trap devices

In this study, a sorbent was immobilized inside a needle resulting in the development of a needle trap (NT) device. This device was applied to extract organic components from gaseous samples and to introduce an enriched mixture into a conventional gas chromatography (GC) injector. Construction of this simple and integrated sampling/extraction/sample introduction device was optimized by considering different ways to immobilize a sorbent in the needle, packing single and multiple-layer sorbent beds, and applying different desorption strategies into the GC injector. A carrier gas system was modified to minimize the carryover for the needle trap with a sealed tip (NT-1), and a narrow-neckliner was used for the blunt-tip needle trap (NT-2). Breakthrough in the device was investigated by connecting two NT-2 devices in series. The needle trap performed very well as an exhaustive spot sampler, as well as in a time-weighted average (TWA) operation. The linear velocity of the mobile phase has no influence on the sampling rate of the needle trap. Validation results against the standard NIOSH 1501 method using charcoal tubes for indoor air surveys demonstrated good accuracy for the NT approach. The reproducibility of the NT-2 was about 1% for benzene. The detection limits for FID detection and for 25 ml gas sample were 0.23 ng/l, 2.10 ng/l and 1.12 ng/l for benzene, ethylbenzene and o-xylene, respectively.     

Application of solid phase microextraction and needle trap device with silica composite of carbon nanotubes for determination of perchloroethylene in laboratory and field

In this paper solid phase microextraction (SPME) and needle trap device (NTD) as two in-progress air monitoring techniques was applied with silylated composite of carbon nanotubes for sampling and analysis of perchloroethylene in air. Application of SPME and NTD with proposed nano-structured sorbent was investigated under different laboratory and experimental parameters and compared to the SPME and NTD with CAR/PDMS. Finally the two samplers contained nano-sorbent used as a field sampler for sampling and analysis of perchloroethylene in dry cleaning. Results revealed that silica composite form of CNTs showed better performance for adsorbent of perchloroethylene. SPME and NTD with proposed sorbent was demonstrated better responses in lower levels of temperature and relative humidity. For 5 days from sampling the relative responses were more than 97% and 94% for NTD and SPME, respectively. LOD were 0.023 and 0.014 ng mL⁻¹ for SPME coated CNTs/SC and CAR/PDMS, and 0.014 and 0.011 ng mL⁻¹ for NTD packed with CNTs/SC and CAR/PDMS, respectively. And for consecutive analysis RSD were 3.9–6.7% in laboratory and 4.43–6.4% in the field. In the field study, NTD was successfully applied for determining of the PCE in dry cleaning. The results show that the NTD packed with nanomaterial is a reliable and effective approach for the sampling and analysis of volatile compounds in air.     

A Modified Nanoporous Silica Aerogel as a New Sorbent for Needle Trap Extraction of Chlorobenzenes from Water Samples

In this work, a modified nanoporous silica aerogel was used as a new sorbent for headspace needle trap extraction of chlorobenzenes from aqueous samples. The needle trap extraction is derived from solid-phase microextraction and the sorbent is inside the needle. The thermal stability and functional groups of the sorbent were studied by TG/DTA and FT-IR, respectively. The modified silica aerogels, characterized by field emission scanning electron microscopy, showed a three-dimensional network containing a homogeneous pore structure with pore sizes of a few tens of nm and a sponge-like microstructure. The developed method was applied to the trace level extraction of some chlorobenzene compounds from aqueous samples. The influential parameters on the extraction efficiency, including the extraction temperature, ionic strength and extraction time were investigated and optimized. Under optimized conditions, the detection and quantification limits were in the range of 0.4–0.8 and 1–3 ng L^?1, respectively. The relative standard deviation values for water spiked with chlorobenzenes at 100 ng L^?1 under optimum conditions were 3–7%. The dynamic linear range of the method in the range of 3–3000 ng L^?1 was investigated. Finally, the current method for the analysis of real water samples containing spiked chlorobenzenes was applied and the relative recovery values were found to be in the range of 96–101%.     

Needle‐trap device for the sampling and determination of chlorinated volatile compounds

A needle‐trap device, with immobilized sorbent inside the syringe, coupled with GC–MS was applied for air sampling and determination of chlorinated volatile organic compounds such as dichloromethane, trichloromethane, and tetrachloromethane. The application of a needle trap packed with combination of three sorbents including Tenax TA, Carbopack X, and Carboxen 1000 resulted in detection limits of few pg for chlorinated volatile compounds and recoveries of 99.2–102.8%. The extraction and desorption parameters were optimized within the study. As a result, the precision determined as RSD was equal to 5.05 and 3.03 and 6.52% for dichloromethane, trichloromethane, and tetrachloromethane, respectively. The storage time for chlorinated compounds up to 48 h and reusability of the needle‐trap device were verified. The obtained results have proved the ability of needle traps to compete with other solventless sampling and sample preparation extraction techniques.     

A novel needle trap sorbent based on carbon nanotube-sol-gel for microextraction of polycyclic aromatic hydrocarbons from aquatic media

A new type of composite material based on carbon nanotubes (CNTs) and sol–gel chemistry was prepared and used as sorbent for needle trap device (NTD). The synthesized composite was prepared in a way to disperse CNTs molecules in a sol–gel polymeric network. CNT/silica composites with different CNT doping levels were successfully prepared, and the extraction capability of each composite was evaluated. Effects of surfactant and the oxidation duration of CNTs on the extraction efficiency of synthesized composites were also investigated. The applicability of the synthesized sorbent was examined by developing a method based on needle trap extraction (NTE) and gas chromatography mass spectrometry detection (GC–MS) for the determination of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Important parameters influencing the extraction process were optimized and an extraction time of 30 min at 50 °C and sampling flow rate of 2.5 mL min⁻¹ gave maximum peak area, when NaCl (15%, w/v) was added to the aqueous sample. The linearity for acenaphthene, acenaphthylene and fluorene was in the concentration range of 0.01–20 ng mL⁻¹ and for naphthalene and anthracene was in the range of 0.1–50 ng mL⁻¹. Limits of detection was 0.001 ng mL⁻¹, for acenaphthene, acenaphthylene and fluorene, and 0.01 ng mL⁻¹, for naphthalene and anthracene using time-scheduled selected ion monitoring (SIM) mode, and the RSD% values (n = 3) were all below 11.2% at the 1 ng mL⁻¹ level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 73.8 to 113.8%.     

A needle trap device packed with a sol–gel derived,multi-walled carbon nanotubes/silica composite for sampling and analysis of volatile organohalogen compounds in air

A needle trap device (NTD) packed with silica composite of multi-walled carbon nanotubes (MWCNTs) prepared based on sol–gel technique was utilized for sampling and analysis of volatile organohalogen compounds (HVOCs) in air. The performance of the NTD packed with MWCNTs/silica composite as sorbent was examined in a variety of sampling conditions and was compared with NTDs packed with PDMS as well as SPME with Carboxen/PDMS-coated fibers. The limit of detection of NTDs for the GC/MS detection system was 0.01–0.05 ng mL⁻¹ and the limit of quantitation was 0.04–0.18 ng mL⁻¹. The RSD were 1.1–7.8% for intra-NTD comparison intended for repeatability of technique. The NTD-MWCNTs/silica composite showed better analytical performances compared to the NTD-PDMS composite and had the same analytical performances when compared to the SPME-Carboxen/PDMS fibers. The results show that NTD-MWCNTs-GC/MS is a powerful technique for active sampling of occupational/environmental pollutants in air.     

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

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

Solvent-free microextraction techniques in gas chromatography

Microextraction techniques represent a major part of modern sample preparation in the analysis of organic micropollutants. This article provides a short overview of recent developments in solvent-free microextraction techniques. From the first open-tubular trap techniques in the mid-1980s to recent packed-needle devices, different implementations of in-needle packings for microextraction are discussed with their characteristic benefits, shortcomings and possible sampling modes. Special emphasis is placed on methods providing full automation and solvent exclusion. In this context, in-tube extraction and the needle trap are discussed, with an overview of current research on new sorbent materials, together with the requirements for more efficient method development.     

Simultaneous extraction and preconcentration of aniline,phenol, and naphthalene using magnetite–graphene oxide composites before gas chromatography determination

The coextraction of acidic and basic compounds from different mediums is a significant concept in sample preparation. In this work, simultaneous extraction of acidic, basic, and neutral analytes in a single step was carried out for the first time. This procedure employed the dispersive solid‐phase microextraction of analytes with magnetic graphene oxide (graphene oxide/Fe₃O₄) sorbent followed by gas chromatography with flame ionization detection. After the adsorption of analytes by vortexing and decantation of the supernatant with a magnet, the sorbent was eluted with acetonitrile/methanol (2:1) mixture. The parameters affecting the extraction efficiency were optimized and obtained as follows: sorbent amount 60 mg, desorption time 1 min, extraction time 5 min, pH of the sample 7, sample volume 20 mL, and elution solvent volume 0.3 mL. Under the optimum conditions, linear dynamic ranges were achieved in the range of 0.5–4, 0.25–4, and 0.25–2 μg/mL and limits of detection were 0.341, 0.110, and 0.167 μg/mL for aniline, phenol, and naphthalene, respectively. The relative standard deviations were in the range of 3.3–5.7% in eight repeated extractions. Finally, the applicability of the method was evaluated by the extraction and determination of analytes in stream water and drinking water samples and satisfactory results were obtained.     

Application of polyaniline–multiwalled carbon nanotubes composite fiber for determination of benzaldehyde in injectable pharmaceutical formulations by solid-phase microextraction GC–FID using experimental design

A polyaniline–multiwalled carbon nanotubes composite fiber was electrodeposited onto a platinum wire using cyclic voltammetry. This fiber was used for headspace solid-phase microextraction combined with gas chromatography and flame ionization detector of trace levels of benzaldehyde in some injectable pharmaceutical formulations. Three solid-phase microextraction parameters including temperature, time and stirring rate were investigated simultaneously using a three-level-three-factor Box–Behnken as experimental design on the extraction capability. The as-made fiber has a lifetime of over 300 extractions without any obvious decline in extraction efficiency. At the optimum conditions (extraction temperature 60°C, extraction time 15 min, stirring rate 700 rpm), the method displays excellent linearity over the concentration range of 25–1000 ng/mL of benzaldehyde with RSD values ranging from 1.0 to 6.8%. The limits of quantitation and detection were 25 and 10 ng/mL, respectively.     

Gas chromatography analysis of benzene, toluene, ethylbenzene and xylenes using newly designed needle trap device in aqueous samples

A newly designed needle trap device with Carbopack X as a sorbent material is used for sampling, preconcentration and injection of volatile analytes benzene, toluene, ethylbenzene and xylenes (BTEX) into gas chromatograph. The closed system of stripping the analytes from water samples was used. An injection port with a modified metal liner was used to desorb analytes trapped in needle trap device. The main advantage of needle trap device consists in the simple methodology and easiness and rapidity of the analysis. Needle trap device is suitable for sampling in field. The experimental parameters as breakthrough volume of stripping gas, linearity, repeatability and limit of detection (LOD) and quantification (LOQ) were investigated. LOD ranges from 0.05 to 0.07 microgL(-1) and relative standard deviation ranges from 0.5% to 11.6% at concentrations 5 and 0.1 microgL(-1), respectively.     

烟草挥发性有机物的高效采样分析技术研究进展

烟草挥发性有机物(Volatile organic compounds,VOCs)含量低、组成复杂、挥发性强,同时烟草及其产品基体极其复杂,发展烟草VOCs的高效采样分析技术具有重要意义。该文综述了近年来烟草VOCs分离富集介质(如石墨烯及其复合材料、硅基材料、磁性富集材料等)及相关采样技术(如QuEChERS技术、固相微萃取技术、液相微萃取技术等)的研究进展,总结了烟草VOCs分析技术在烟草产品质量控制等方面的实际应用情况,并展望了该领域的未来研究趋势。     

Polyurethane/polystyrene‐silica electrospun nanofibrous composite for the headspace solid‐phase microextraction of chlorophenols coupled with gas chromatography

A novel electrospun composite nanofiber‐based adsorbent (polyurethane/polystyrene‐silica) was fabricated, characterized, and used in the headspace solid‐phase microextraction of the acetylated derivatives of chlorophenols in water samples before gas chromatography with micro electron capture detection. The surface morphology, chemical composition, thermal stability, and structure of the fibers were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller and Barrett–Joyner–Halenda techniques. The effect of the main parameters influencing the efficiency of the method including extraction temperature, salt concentration, and extraction time was investigated and the optimized conditions were obtained. The linear dynamic ranges were 0.1–800 ng/mL. The relative standard deviations (n = 3) and the limits of detection were 2.64–9.57% and 0.0234–0.830 ng/mL, respectively. The relative recoveries for real samples (river water and sewage of our university campus) were between 90.8 and 111%.     

Preparation and application of a polythiophene solid‐phase microextraction fiber for the determination of endocrine‐disruptor pesticides in well waters

A robust solid‐phase microextraction fiber was fabricated by electropolymerization of thiophene on a stainless steel wire. This fiber was applied for the determination of endocrine‐disruptor pesticides, namely, chlorpyrifos, penconazole, procymidone, bromopropylate, and λ‐cyhalothrin in well waters by a headspace solid‐phase microextraction procedure. Operational parameters, namely, pH, sample volume, adsorption temperature and time, desorption temperature, stirring rate, and salt amount were optimized as 7.0, 8 mL, 70°C and 20 min, 250°C, 600 rpm, and 0.3 g/mL, respectively. The separation power of GC was coupled with the excellent sensitivity of the developed fiber enabling us to determine pesticide mixtures simultaneously in a ng/mL range. The LOD was in the range of 0.02–0.64 ng/mL. The method was successfully applied for the selective and sensitive determination of target pesticides in well water samples with acceptable recovery values (92–110%). The polythiophene fiber gives satisfactory results compared with commercial fibers. Commonly used pesticides with different polarities were chosen as representative compounds to search the applicability of the fiber for well water analysis collected from vineyards.     

Collection method for chemical particulates on surfaces with detection using thermal desorption-ion trap mass spectrometry

Successful analysis of particulate/low vapor pressure analytes such as explosives and toxic chemicals, and commercial pesticides require new sampling tools that enable detection of these analytes using current vapor phase detection instruments. We describe a sampling approach that uses stainless steel screens coated with a sticky polydimethyl siloxane (PDMS) coating to capture particulates from surfaces. Preliminary results for the collection of dimethyl methylphosphonate (DMMP) sorbed onto silica gel (SG) particulates (DMMP/SG) from a surface with subsequent analysis by thermal desorption-cylindrical ion trap mass spectrometry (TD-CITMS) are reported.     

Application of carbon nanotubes modified with a Keggin polyoxometalate as a new sorbent for the hollow‐fiber micro‐solid‐phase extraction of trace naproxen in hair samples with fluorescence spectrophotometry using factorial experimental design

A sensitive technique to determinate naproxen in hair samples was developed using hollow‐fiber micro‐solid‐phase combined with fluorescence spectrophotometry. The incorporation of multi‐walled carbon nanotubes modified with a Keggin polyoxometalate into a silica matrix prepared by the sol–gel method was reported. In this research, the Keggin carbon nanotubes /silica composite was used in the pores and lumen of a hollow fiber as the hollow‐fiber micro‐solid‐phase extraction device. The device was used for the microextraction of the analyte from hair and water samples under the optimized conditions. An orthogonal array experimental design with an OA24 (4⁶) matrix was employed to optimize the conditions. The effect of six factors influencing the extraction efficiency was investigated: pH, salt, volume of donor and desorption phase, extraction and desorption time. The effect of each factor was estimated using individual contributions as response functions in the screening process. Analysis of variance was employed for estimating the main significant factors and their contributions in the extraction. Calibration curve plot displayed linearity over a range of 0.2–10 ng/mL with detection limits of 0.072 and 0.08 ng/mL for hair and aqueous samples, respectively. The relative recoveries in the hair and aqueous matrices ranged from 103–95%. The relative standard deviation for fiber‐to‐fiber repeatability was 3.9%.     

Synthesis of a metal–organic framework confined in periodic mesoporous silica with enhanced hydrostability as a novel fiber coating for solid‐phase microextraction

A metal–organic framework/periodic mesoporous silica (MOF‐5@SBA‐15) hybrid material has been prepared by using SBA‐15 as a matrix. The prepared MOF‐5@SBA‐15 hybrid material was then deposited on a stainless‐steel wire to obtain the fiber for the solid‐phase microextraction of phenolic compounds. Modifications in the metal–organic framework structure have proven to improve the extraction performance of MOF/SBA‐15 hybrid materials, compared to pure MOF‐5 and SBA‐15. Optimum conditions include an extraction temperature of 75°C, a desorption temperature of 260°C, and a salt concentration of 20% w/v. The dynamic linear range and limit of detection range from 0.1–500 and from 0.01–3.12 ng/mL, respectively. The repeatability for one fiber (n = 3), expressed as relative standard deviation, is between 4.3 and 9.6%. The method offers the advantage of being simple to use, rapid, and low cost, the thermal stability of the fiber, and high relative recovery (compared to conventional methods) represent additional attractive features.     

Electromembrane‐surrounded solid‐phase microextraction coupled to ion mobility spectrometry for the determination of nonsteroidal anti‐inflammatory drugs: A rapid screening method in complicated matrices

A new robust method of electromembrane‐surrounded solid‐phase microextraction coupled to ion mobility mass spectrometry was applied for nonsteroidal anti‐inflammatory drugs determination in complex matrices. This is the first time that a graphene/polyaniline composite coating is applied in electromembrane‐surrounded solid‐phase microextraction method. The homemade graphene/polyaniline composite is characterized by a high electrical conductivity and thermal stability. The variables affecting electromembrane‐surrounded solid‐phase microextraction, including extraction time; applied voltage and pH were optimized through chemometric methods, central composite design, and response surface methodology. Under the optimized conditions, limits of detection of 0.04 and 0.05 ng/mL were obtained for mefenamic acid and ibuprofen, respectively. The feasibility of electromembrane‐surrounded solid‐phase microextraction followed by ion mobility mass spectrometry was successfully confirmed by the extraction and determination of low levels of ibuprofen and mefenamic acid in human urine and plasma samples and satisfactory results were obtained.     

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.