Highly porous solid-phase microextraction fiber coating based on poly(ethylene glycol)-modified ormosils synthesized by sol-gel technology

The preparation and characteristics of solid-phase microextraction (SPME) fibers coated with Carbowax 20M ormosil (organically modified silica) are described here. Raw fused silica fibers were coated with Carbowax 20M-modified silica using sol-gel process. Scanning electron micrographs of fibers revealed a highly porous, sponge-like coating with an average thickness of (8 +/- 1) microm. The sol-gel Carbowax fibers were compared to commercial fibers coated with 100 microm polydimethylsiloxane (PDMS) and 65 microm Carbowax-divinylbenzene (DVB). Shorter equilibrium times were possible with the sol-gel Carbowax fiber: for headspace extraction of the test analytes, they ranged from less than 3 min for benzene to 15 min for o-xylene. Extraction efficiencies of the sol-gel Carbowax fiber were superior to those of conventional fibers: for o-xylene, the extracted masses were 230 and 540% of that obtained with 100 microm PDMS and 65 microm Carbowax-DVB fibers, respectively.     

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.     

Considerations on Static and Dynamic Sorptive and Adsorptive Sampling to Monitor Volatiles Emitted by Living Plants

Static and dynamic headspace sampling have been applied for the enrichment of volatiles emitted by living plants. For solid phase microextraction (SPME) the sorptive fibers polydimethylsiloxane (PDMS) and polyacrylate (PA) have been compared and, in accordance with the like‐like principle, polar compounds exhibit more affinity for the PA fiber while apolar solutes favor the PDMS fiber. For dynamic sampling, tubes packed with PDMS particles show greater inertness than Tenax; some Tenax decomposition products, e.g. benzaldehyde and acetophenone, interfere with the analyses. With PDMS particles operated in the breakthrough mode, the obtained profiles are similar to those obtained by SPME on the PA fiber. Recoveries relative to a packed PDMS bed are 85% for Tenax, 2.4% for SPME‐PDMS, and 6.2% for SPME‐PA.     

A new polyethylene glycol fiber prepared by coating porous zinc electrodeposited onto silver for solid-phase microextraction of styrene

A new polyethylene glycol fiber was developed for solid-phase microextraction (SPME) of styrene by electrodepositing porous Zn film on Ag wire substrate followed by coating with polyethylene glycol sol-gel (Ag/Zn/PEG sol-gel fiber). The scanning electron micrographs of fibers surface revealed a highly porous structure. The extraction property of the developed fiber-to-styrene residue from polystyrene packaged food was investigated by headspace solid-phase microextraction (HS-SPME) and analyzed with a gas chromatograph coupled with flame ionization detection (GC-FID). The new Ag/Zn/PEG sol-gel fiber is simple to prepare, low cost, robust, has high thermal stability and long lifetime, up to 359 extractions. Repeatability of one fiber (n = 6) was in the range of 4.7-7.5% and fiber-to-fiber reproducibility (n = 4) for five concentration values were in the range 3.4-10%. This Ag/Zn/PEG sol-gel fiber was compared to two commercial SPME fibers, 75 μm carboxen/polydimethylsiloxane (CAR/PDMS) and 100 μm polydimethylsiloxane (PDMS). Under their optimum conditions, Ag/Zn/PEG sol-gel fiber showed the highest sensitivity and the lowest detection limit at 0.28 ± 0.01 ng mL⁻¹.     

Headspace solid-phase microextraction of oil matrices heated at high temperature and phthalate esters determination by gas chromatography multistage mass spectrometry

A solvent-free analytical approach based on headspace solid-phase microextraction (SPME) of oil matrices heated at high temperatures coupled to gas chromatography with mass spectrometry detector (GC-ion trap) has been developed for the determination of phthalic acid esters (PAEs) in oil matrices without sample manipulation. For this study, three fibers, i.e., 85 μm-polyacrylate (PA), 50/30 μm-divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/PDMS) and 100 μm-polydimethylsiloxane (PDMS) were tested. Variables affecting the SPME headspace composition such as incubation sample temperature, sample incubation time and fiber exposition time were optimized. The optimal values found were 250 °C for sample incubation temperature and 30 min for incubation and extraction time. PA fiber was not suitable for the lightest polar phthalates which showed poor extraction and repeatability values. PDMS fiber had very poor response for some of the heavier and non-polar phthalates, whereas DVB/CAR/PDMS fiber showed the best response and repeatability values for the majority of the phthalates studied. The main benefit of the analytical method proposed is the absence of sample manipulation and hence avoidance of possible contamination coming from glassware, environment, solvents and samples.     

Use of solid-phase microextraction to detect and quantify gas-phase dicarbonyls in indoor environments

Solid-phase microextraction (SPME) was evaluated for the detection and quantification of the gas-phase dicarbonyls, glyoxal (GLY) and methylglyoxal (MGLY). Additionally, polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), and carbowax/divinylbenzene (CW/DVB) fibers were tested to determine the optimum fiber for detection of these species. GLY and MGLY were derivatized with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PFBHA), extracted with SPME from headspace or bag chamber and then analyzed by GC/MS. The PDMS/DVB SPME fiber for on-fiber derivatization and subsequent sampling for gas-phase methylglyoxal provided the optimum combination of analytical reproducibility and sensitivity. Linearity of the calibration curve was achieved across a range of 11-222 microg/m(3) (4-75 ppb).     

Flavour analysis of Greek white wine by solid-phase microextraction-capillary gas chromatography-mass spectrometry

Solid-phase microextraction (SPME) was optimised for the qualitative determination of the volatile flavour compounds responsible for the aroma of Greek Boutari wine. Several factors influencing the equilibrium of the aroma compounds between the sample and the SPME fiber were taken into account, including the extraction time, the extraction temperature, the sampling mode (headspace and direct immersion or liquid SPME), and the presence of salt. Four different SPME fibers were used in this study. namely poly(dimethylsiloxane) (PDMS), poly(acrylate), carbowax-divinylbenzene and divinylbenzene-carboxen on poly(dimethylsiloxane). The best results were obtained using the PDMS fiber during headspace extraction at 25 degrees C for 30 min after saturating the samples with salt. The optimised SPME method was then applied to investigate the qualitative aroma composition of three other Greek wines, namely Zitsa, Limnos and Filoni.     

Solid-phase microextraction for determining the distribution of sixteen US Environmental Protection Agency polycyclic aromatic hydrocarbons in water samples

A solid-phase microextraction (SPME) procedure has been developed for the determination of 16 US Environmental Protection Agency promulgated polycyclic aromatic hydrocarbons (PAHs). Five kinds of SPME fibers were used and compared in this study. The extracted sample was analyzed by gas chromatography with flame ionization detection or mass spectrometry. Parameters affecting the sorption of analyte into the fibers, including sampling time, thickness of the fiber coating, and the effect of temperature, have been examined. Moreover, the feasibility of headspace SPME with different working temperatures was evaluated. The method was also applied to real samples. The 85-microm polyacrylate (PA) and 100-microm poly(dimethylsiloxane) (PDMS) fibers were shown to have the highest affinities for the selected PAHs. The PA fiber was more suitable than the PDMS fiber for the determination of low-ring PAHs while high sensitivity of high-ring PAHs was observed when a 100-microm PDMS fiber was used. The method showed good linearity between 0.1 and 100 ng/ml with regression coefficients ranging from 0.94 to 0.999. The reproducibility of the measurements between fibers was found to be very good. The precisions of PA and PDMS fibers were from 3 to 24% and from 3 to 14%, respectively. Headspace SPME is a valid alternative for the determination of two- to five-ring PAHs. A working temperature of 60 degrees C provides significant enhancement in sensitivity of two- to five-ring PAHs having low vapor pressures (>10(-6) mmHg at 25 degrees C) (1 mmHg = 133.3 Pa) and low Henry's constants (>10 atm ml/mol) (1 atm = 1.01 x 10(5) Pa).     

Preparation and application of poly(dimethylsiloxane)/beta-cyclodextrin solid-phase microextraction fibers

A novel poly(dimethylsiloxane)/beta-cyclodextrin (PDMS/beta-CD) coating was prepared for solid-phase microextraction (SPME). The PDMS/beta-CD coating proved to have a porous structure, providing high surface areas and allowing for high extraction efficiency. The coating had a high thermal stability (340 degrees C) and a long lifetime due to its chemical binding to the fiber surface. Polar phenols and amines were used to evaluate the character of the coating fiber by headspace (HS) extraction and thermal desorption, followed by GC-FID analysis. Parameters that affected the extraction process were investigated; these include extraction time and temperature, desorption time, pH, and ionic strength of the solution. For phenols, the range of linearity of the method was 4-500 microg/L and the LOD was 1.3-2.1 microg/L. For amines, the range of linearity was 1-1000 microg/L and the LOD was 1.2-2.8 microg/L. The presence of beta-CD not only increases the thermal stability of the fiber coating, but also enhances its selectivity. Compared with commercially available SPME fibers, the new phases show better selectivity and sensitivity towards polar compounds.     

Evaluation of solid-phase micro-extraction coupled to gas chromatography-mass spectrometry for the headspace analysis of volatile compounds in cocoa products

The aroma profile of cocoa products was investigated by headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS). SPME fibers coated with 100 μm polydimethylsiloxane coating (PDMS), 65 μm polydimethylsiloxane/divinylbenzene coating (PDMS-DVB), 75 μm carboxen/polydimethylsiloxane coating (CAR-PDMS) and 50/30 μm divinylbenzene/carboxen on polydimethylsiloxane on a StableFlex fiber (DVB/CAR-PDMS) were evaluated. Several extraction times and temperature conditions were also tested to achieve optimum recovery. Suspensions of the samples in distilled water or in brine (25% NaCl in distilled water) were investigated to examine their effect on the composition of the headspace. The SPME fiber coated with 50/30 μm DVB/CAR-PDMS afforded the highest extraction efficiency, particularly when the samples were extracted at 60 °C for 15 min under dry conditions with toluene as an internal standard. Forty-five compounds were extracted and tentatively identified, most of which have previously been reported as odor-active compounds. The method developed allows sensitive and representative analysis of cocoa products with high reproducibility. Further research is ongoing to study chocolate making processes using this method for the quantitative analysis of volatile compounds contributing to the flavor/odor profile.     

固相微萃取气相色谱法测定水相中邻苯二甲酸二酯

 采用m(聚硅氧烷 (OV 1) )∶m (富勒烯聚二甲基硅氧烷 (PSO C60 ) ) =4∶1的混合固定相自制萃取头 ,利用顶空固相微萃取与气相色谱联用技术 (HS SPME GC)分析了水中 5种邻苯二甲酸二酯。考察了萃取温度、离子强度、吸附和热解吸时间等因素对该方法灵敏度的影响。结果表明该萃取头萃取选择性优于商用PDMS萃取头。方法的检出限为 0 331ng/L～ 12 5 μg/L ;除邻苯二甲酸二正壬酯外 ,相对标准偏差均在 12 %以下。     

Physically incorporated extraction phase of solid-phase microextraction by sol-gel technology

A sol-gel method for the preparation of solid-phase microextraction (SPME) fiber was described and evaluated. The extraction phase of poly(dimethysiloxane) (PDMS) containing 3% vinyl group was physically incorporated into the sol-gel network without chemical bonding. The extraction phase itself is then partly crosslinked at 320 degrees C, forming an independent polymer network and can withstand desorption temperature of 290 degrees C. The headspace extraction of BTX by the fiber SPME was evaluated and the detection limit of o-xylene was down to 0.26 ng/l. Extraction and determination of organophosphorus pesticides (OPPs) in water, orange juice and red wine by the SPME-GC thermionic specified detector (TSD) was validated. Limits of detection of the method for OPPs were below 10 ng/l except methidathion. Relative standard deviations (RSDs) were in the range of 1-20% for pesticides being tested.     

Determination of sulphur compounds in beer using headspace solid-phase microextraction and gas chromatographic analysis with pulsed flame photometric detection

A simple and sensitive method for the analysis of volatile and semi-volatile sulphur compounds in beer at trace levels was developed using headspace solid-phase microextraction (SPME) and gas chromatography with pulsed flame photometric detection. Different SPME fibres were tested and a Carboxen-polydimethylsiloxane coated fibre was found to be the most appropriate. The adsorption and desorption conditions were optimised. The effect of ethanol concentration in the sample on the extraction of analytes was examined. A 60 m non-polar capillary column preceded by a 10 m length of a polar column was found to be capable of separating a wide range of C1-C6 sulphur compounds. The pulsed flame photometric detector enabled increased sensitivity to be obtained over previous methods, such as dynamic headspace followed by conventional flame photometric detection or sulphur chemiluminescent detection, with high sulphur selectivity. Two sulphur compounds, 2-methyl-1-butanethiol and 3-methylthiophene, were identified in beer for the first time.     

Selective solid-phase microextraction of explosives using fibers coated with the La(III) complex of p-di(4,4,5,5,6,6,6-heptafluoro-1,3-hexanedionyl)benzene

This research demonstrates enhanced capture of explosives on polydimethylsiloxane (PDMS) solid-phase microextraction (SPME) fibers coated with a metal beta-diketonate polymer, [La(III) complex of p-di(4,4,5,5,6,6,6-heptafluoro-1,3-hexanedionyl)benzene, La(dihed)], compared to PDMS control fibers. SPME sampling was performed in an explosives bunker where the concentration of 2,4,6-trinitrotoluene (TNT) was estimated at less than 3parts-per-trillion (v/v). Analysis by gas chromatography/mass spectrometry showed an approximate 10-fold enhancement in the quantity of 2,4-dinitrotoluene captured on La(dihed) over the control fiber. La(dihed) sampling also resulted in a strong signal for TNT, whereas this explosive was well below the detection limit (1pg on fiber) on the control fiber.     

Optimization of a sensitive method for the determination of nitro musk fragrances in waters by solid-phase microextraction and gas chromatography with micro electron capture detection using factorial experimental design

A solid-phase microextraction method (SPME) followed by gas chromatography with micro electron capture detection for determining trace levels of nitro musk fragrances in residual waters was optimized. Four nitro musks, musk xylene, musk moskene, musk tibetene and musk ketone, were selected for the optimization of the method. Factors affecting the extraction process were studied using a multivariate approach. Two extraction modes (direct SPME and headspace SPME) were tried at different extraction temperatures using two fiber coatings [Carboxen–polydimethylsiloxane (CAR/PDMS) and polydimethylsiloxane–divinylbenzene (PDMS/DVB)] selected among five commercial tested fibers. Sample agitation and the salting-out effect were also factors studied. The main effects and interactions between the factors were studied for all the target compounds. An extraction temperature of 100 °C and sampling the headspace over the sample, using either CAR/PDMS or PDMS/DVB as fiber coatings, were found to be the experimental conditions that led to a more effective extraction. High sensitivity, with detection limits in the low nanogram per liter range, and good linearity and repeatability were achieved for all nitro musks. Since the method proposed performed well for real samples, it was applied to different water samples, including wastewater and sewage, in which some of the target compounds (musk xylene and musk ketone) were detected and quantified. Figure Stardardized Pareto charts for the main effects and interactions     

Nitrogen isotope analysis of ammonium in aqueous solutions using a perfluorosulfonated ionomer membrane for solid-phase microextraction

The use of custom-made solid-phase microextraction (SPME) fibers coated with a perfluorosulfonated ionomer, Nafion, was investigated for nitrogen isotopic analysis of ammonium in aqueous solutions. Aqueous ammonium was converted to ammonia by addition of a base, followed by absorption from the headspace, desorption in the injection port of a gas chromatograph, and analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Fibers coated with a Nafion tubing were chosen due to a higher fiber-gas distribution constant and a higher Nafion thickness than fibers coated with Nafion solution, both leading to a higher amount of ammonia absorbed at equilibrium. The Nafion membrane-coated fiber absorbed approximately 20 times more than a commercial polydimethylsiloxane (PDMS) fiber. The isotopic fractionation between fiber and gas was 1.0117 +/- 0.0009 (standard deviation, SD, of all measurements) at an initial ammonia gas concentration of 21-210 microM. At 390 microM initial gas concentration it was slightly lower. When sampling from liquid samples, an ammonium concentration of 10 mM was needed to obtain a sufficient amount of ammonia absorbed. Modeling of the absorption at different temperatures showed that the absorption was approximately constant in the temperature range suitable for SPME experiments. Absorption at room temperature was therefore used for simplicity. A pilot study was conducted in which absorption was achieved from a single 9 microL droplet of sample. The preliminary results showed that delta(15)N analysis was possible for only 0.4-0.5 micromol of ammonium with a SD of 0.8 per thousand (n = 5).     

Quality assessment of Flos Chrysanthemi Indici from different growing areas in China by solid-phase microextraction-gas chromatography-mass spectrometry

Flos Chrysanthemi Indici is a common traditional Chinese medicine (TCM). In this paper, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was developed for quality assessment of Flos Chrysanthemi Indici from different growing areas in China. SPME parameters such as extraction fibers, extraction temperature, extraction time and sample mass were investigated to achieve identical results to those obtained by the steam distillation (SD). The selected SPME conditions were as follows: SPME fiber coated with 65-microm PDMS/DVB, extraction temperature of 60 degrees C, extraction time of 30 min and sample mass of 1.0 g. Furthermore, four active compounds (eucalyptol, camphor, borneol and bornyl acetate) presented in the TCM were applied to evaluating the quality of Flos Chrysanthemi Indici from 20 various areas. The quality assessment was successfully performed to compare the similarity value (S) between different sample vector of Flos Chrysanthemi Indici and the standard profile vector (SPV). The results showed that the proposed HS-SPME-GC-MS was an alternative technique for quality assessment of Flos Chrysanthemi Indici samples.     

Development of a Sol-Gel Procedure for Preparation of a Diglycidyloxycalix[4]arene Solid-Phase Microextraction Fiber with Enhanced Extraction Efficiency

5,11,17,23-Tetra-tert-butyl-25,27-dihydroxy-26,28-diglycidyloxycalix[4]arene (diglycidyloxy-C[4]) has been synthesized and used for preparation of a sol-gel solid-phase microextraction fiber with enhanced extraction efficiency. The sol-gel procedure was developed using a sol solution containing diglycidyloxy-C[4] as organic component and both tetraethoxysilane and 3-aminopropyltriethoxysilane (KH-550) as precursors. No additional catalysts were used and no centrifugation was performed. Diglycidyloxy-C[4] was highly chemically reactive toward KH-550 even at room temperature, which increased the calixarene content of the coating, simplified the sol-gel procedure, reduced the sol-gel reaction time, enhanced the polarity of the coating, and improved extraction performance. The sol-gel mixture also had very good coating properties and was highly uniformly distributed on the surface of the fiber; because of these characteristics several fibers could be prepared from one sol-gel solution. Efficient extraction of trace analytes (µg L^?1 levels) from aqueous samples was accomplished using this kind of new fiber. Very low detection limits (ng L^?1 level) were achieved for most polar (aromatic amines and phenols) and nonpolar (polycyclic aromatic hydrocarbons) aromatic compounds by SPME followed by gas chromatography with flame ionization detection. The new coating had excellent solvent and thermal (350 °C) stability. Lifespan was also good—a fiber could be used more than 300 times in headspace SPME without substantial changes in the properties of the coating.     

Laboratory and field experiments used to identify<Emphasis Type="Italic"> Canis lupus</Emphasis> var. <Emphasis Type="Italic">familiaris</Emphasis> active odor signature chemicals from drugs,explosives, and humans

This paper describes the use of headspace solid-phase microextraction (SPME) combined with gas chromatography to identify the signature odors that law enforcement-certified detector dogs alert to when searching for drugs, explosives, and humans. Background information is provided on the many types of detector dog available and specific samples highlighted in this paper are the drugs cocaine and 3,4-methylenedioxy-N-methylamphetamine (MDMA or Ecstasy), the explosives TNT and C4, and human remains. Studies include the analysis and identification of the headspace "fingerprint" of a variety of samples, followed by completion of double-blind dog trials of the individual components in an attempt to isolate and understand the target compounds that dogs alert to. SPME–GC/MS has been demonstrated to have a unique capability for the extraction of volatiles from the headspace of forensic specimens including drugs and explosives and shows great potential to aid in the investigation and understanding of the complicated process of canine odor detection. Major variables evaluated for the headspace SPME included fiber chemistry and a variety of sampling times ranging from several hours to several seconds and the resultant effect on ratios of isolated volatile components. For the drug odor studies, the CW/DVB and PDMS SPME fibers proved to be the optimal fiber types. For explosives, the results demonstrated that the best fibers in field and laboratory applications were PDMS and CW/DVB, respectively. Gas chromatography with electron capture detector (GC/ECD) and mass spectrometry (GC/MS) was better for analysis of nitromethane and TNT odors, and C-4 odors, respectively. Field studies with detector dogs have demonstrated possible candidates for new pseudo scents as well as the potential use of controlled permeation devices as non-hazardous training aids providing consistent permeation of target odors.     

Modified Polypyrrole with Tetrasulfonated Nickel Phthalocyanine as a Fiber for Solid-Phase Microextraction. Application to the Extraction of BTEX Compounds from Water Samples

Gold wire was coated with polypyrrole (PPY) by electropolymerization and used as a solid-phase microextraction (SPME) fiber. The adsorptive property of the coating was modified by doping with tetrasulfonated nickel phthalocyanine (NiPcTS). The efficiency and reliability of this fiber was investigated for the extraction of BTEX compounds from the headspace of water samples. Monitoring of extraction efficiency was performed by capillary GC-FID. Effects of several factors such as electropolymerization time, salt addition, exposure time and stirring speed on extraction efficiency were studied. The calibration graphs were linear in the range of 0.06 to 50 ng mL^?1 and the detection limits for BTEX compounds were 20–50 pg mL^?1. Comparing the results obtained using these fibers with results reported in the literature with polydimethylsiloxane (PDMS) fibers shows that under optimum conditions, the detection limits are comparable.