Coated Solid-phase Microextraction Fiber Research Articles

Solid-Phase Microextraction and the Human Fecal VOC Metabolome

The diagnostic potential and health implications of volatile organic compounds (VOCs) present in human feces has begun to receive considerable attention. Headspace solid-phase microextraction (SPME) has greatly facilitated the isolation and analysis of VOCs from human feces. Pioneering human fecal VOC metabolomic investigations have utilized a single SPME fiber type for analyte extraction and analysis. However, we hypothesized that the multifarious nature of metabolites present in human feces dictates the use of several diverse SPME fiber coatings for more comprehensive metabolomic coverage. We report here an evaluation of eight different commercially available SPME fibers, in combination with both GC-MS and GC-FID, and identify the 50/30 µm CAR-DVB-PDMS, 85 µm CAR-PDMS, 65 µm DVB-PDMS, 7 µm PDMS, and 60 µm PEG SPME fibers as a minimal set of fibers appropriate for human fecal VOC metabolomics, collectively isolating approximately 90% of the total metabolites obtained when using all eight fibers. We also evaluate the effect of extraction duration on metabolite isolation and illustrate that ex vivo enteric microbial fermentation has no effect on metabolite composition during prolonged extractions if the SPME is performed as described herein.

Microextracción en fase sólida de compuestos volátiles en albahaca (Ocimum basilicum L.)

Los compuestos volátiles de la albahaca (Ocimum basilicum L.) fueron extraídos mediante la microextracción en fase sólida (SPME) y analizados con cromatografía de gases-espectrometría de masas (GC-MS). Se evaluaron dos fibras, Polidimetilsiloxano/Divinilbenceno (PDMS/DVB, 65 μm) y Carbowax/Divinilbenceno (CW/DVB, 65 μm), para comparar la extracción de componentes. Entre los 25 compuestos volátiles recuperados en la albahaca, se identificaron fenilpropanoides, monoterpenos, sesquiterpenos, ésteres, y aldehídos. Hubieron diferencias significativas (P < 0,05) entre las fibras analizadas. La comparación de las dos fibras mostró que la extracción con la fibra CW/DVB es aparentemente mejor tanto en el número de componentes aislados como en la concentración total de los compuestos. Cuantitativamente, el componente más importante fue el cinamato de metilo, seguido por el linalol.

New coated SPME fibers for extraction and fast HPLC determination of selected drugs in human blood

Polythiophene (PTh) and polypyrrole (PPy) as sorbent phases for solid phase microextraction (SPME) were applied in order to extract the multi-resistant Staphylococcus aureus (MRSA) antibiotic drugs (linezolid and daptomycin) from whole blood followed by high performance liquid chromatography (HPLC) determination with UV detection. Relative standard deviations (RSDs) of in vitro and pseudo in vivo measurements performed in whole blood were in the range of 4.58–15.91% and 6.09–17.33% for linezolid and daptomycin, respectively. Determination coefficients ( R 2) were in range of 0.9884–0.9945 and 0.9807–0.9818 for linezolid and daptomycin, respectively. This study proved better adsorption capacity of PTh SPME coating compared to PPy coating for both, linezolid and daptomycin.

A novel molecularly imprinted solid-phase microextraction fiber coupled with high performance liquid chromatography for analysis of trace estrogens in fishery samples

The combination of molecular imprinting and solid-phase microextraction (SPME) technique provides a powerful sample preparation tool in terms of selectivity, simplicity, and flexibility. This paper reports a novel molecularly imprinted polymer (MIP) coated SPME fiber with 17beta-estradiol as template by improved multiple co-polymerization method. The obtained fiber exhibits excellent characteristics such as high porosity, good thermal and chemical stability. Extraction performance shows that the MIP-coated fiber has stronger affinity to the template molecule as compared with the commercial SPME fibers and the control polymer-coated fiber without addition of template. Owing to the shape and structural compatibility, the obtained fiber also demonstrated specific selectivity to the structural related compounds of 17beta-estradiol, such as estriol, estrone and 17 alpha-ethynylestradiol, and thus can be applied to simultaneous determination of these estrogens from complex samples coupled with high performance liquid chromatography. The variables that influence extraction were investigated. The MIP-coated fiber demonstrated its efficiency for extraction of estrogens in fishery samples. The detection limits were in the range of 0.98-2.39 microg L(-1), and the recoveries were 80.0-83.6% and 85.0-94.1% for fish and shrimp tissue samples, respectively.

Air Sampling and Analysis Method for Volatile Organic Compounds (VOCs) Related to Field-Scale Mortality Composting Operations

In biosecure composting, animal mortalities are so completely isolated during the degradation process that visual inspection cannot be used to monitor progress or the process status. One novel approach is to monitor the volatile organic compounds (VOCs) released by decaying mortalities and to use them as biomarkers of the process status. A new method was developed to quantitatively analyze potential biomarkers--dimethyl disulfide, dimethyl trisulfide, pyrimidine, acetic acid, propanoic acid, 3-methylbutanoic acid, pentanoic acid, and hexanoic acid--from field-scale biosecure mortality composting units. This method was based on collection of air samples from the inside of biosecure composting units using portable pumps and solid phase microextraction (SPME). Among four SPME fiber coatings, 85 microm CAR/PDMS was shown to extract the greatest amount of target analytes during a 1 h sampling time. The calibration curves had high correlation coefficients, ranging from 96 to 99%. Differences between the theoretical concentrations and those estimated from the calibration curves ranged from 1.47 to 20.96%. Method detection limits of the biomarkers were between 11 pptv and 572 ppbv. The applicability of the prepared calibration curves was tested for air samples drawn from field-scale swine mortality composting test units. Results show that the prepared calibration curves were applicable to the concentration ranges of potential biomaker compounds in a biosecure animal mortality composting unit.

Carbon nanotube-coated solid-phase microextraction metal fiber based on sol–gel technique

A novel carbon nanotube (CNT)-coated solid-phase microextraction fiber was prepared based on sol–gel technique. Commonly used fragile fused silica fiber was replaced with stainless steel wire, which made the fiber unbreakable. An approach was also proposed for batch producing, and good reproducibilities for fiber to fiber and between fibers were achieved. Experiments showed that the sol–gel-CNT fiber exhibited high thermal stability to resist 350 °C and excellent solvent durability in methanol and acetonitrile. Compared to commercial polydimethylsiloxane (PDMS) fiber, the sol–gel-CNT fiber represented significantly improved extraction efficiencies for both polar (phenols) and non-polar (benzene, toluene, ethylbenzene, and o-xylene) compounds. Meanwhile, no replacement effect, low carry-over and wide linear range demonstrated that the newly prepared sol–gel-CNT coating has liquid properties, which allow a relatively easy quantification procedure. Moreover, the characterization of the sol–gel-CNT coating was also evaluated with McReynold probe solutes. The results showed that the coating has better affinity for all the five types of solutes compared to commercial 7 μm PDMS fiber, which suggested that the coating has the potential to be developed as GC stationary phase.

A passive sampler based on solid‐phase microextraction for quantifying hydrophobic organic contaminants in sediment pore water

Sediment-quality assessment often is hindered by the lack of agreement between chemical and biological lines of evidence. One limitation is that the bulk sediment toxicant concentration, the most widely used chemical parameter, does not always represent the bioavailable concentration, particularly for hydrophobic organic compounds (HOCs) in highly contaminated sediments. In the present study, we developed and tested a pore-water sampler that uses solid-phase microextraction (SPME) to measure freely dissolved (bioavailable) HOC concentrations. A single polydimethylsiloxane (PDMS)-coated SPME fiber is secured in a compact, protective housing that allows aqueous exchange with whole sediment while eliminating direct contact with sediment particles. Fibers with three PDMS coating thicknesses were first calibrated for 12 model HOCs of current regulatory concern. Precalibrated samplers were exposed to spiked estuarine sediment in laboratory microcosms to determine the time to equilibrium and the equilibrium concentrations across a range of sediment contamination. Time to equilibrium ranged from 14 to 110 d, with 30 d being sufficient for more than half the target HOCs. Equilibrium SPME measurements, ranging from 0.009 to 2,400 ng/L, were highly correlated with but, in general, lower than HOC pore-water concentrations determined independently by liquid-liquid extraction. This concept shows promise for directly measuring the freely dissolved concentration of HOCs in sediment pore water, a previously difficult-to-measure parameter that will improve our ability to assess the impacts of contaminated sediments.

Feasibility of detection and quantification of gas-phase carbonyls in indoor environments using PFBHA derivatization and solid-phase microextraction (SPME)

Solid-phase microextraction (SPME) was evaluated for the detection and quantification of the gas-phase carbonyls: citronellal, glyoxal, methylglyoxal, and beta-ionone. Prepared air samples containing the carbonyl compounds were collected at a flow rate of 2.8 L min(-1) in an impinger containing a 25% reagent water/75% methanol collection liquid. The aqueous samples were then derivatized with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA), extracted with a PDMS/DVB coated SPME fiber, and analyzed by GC-MS. Detection limits with a sample air volume of 76 L were calculated to be 0.03 ppbv, 0.34 ppbv, 0.12 ppbv, and 0.28 ppbv for citronellal, glyoxal, methylglyoxal, and beta-ionone, respectively.

Simultaneous determination of selegiline and desmethylselegiline in human body fluids by headspace solid-phase microextraction and gas chromatography–mass spectrometry

A method for the simultaneous determination of selegiline and its metabolite, desmethylselegiline, in human whole blood and urine is presented. The method, which combines a fiber-based headspace solid-phase microextraction (SPME) technique with gas chromatography–mass spectrometry (GC–MS), required optimization of various parameters (e.g., salt additives, extraction temperatures, extraction times and the extraction properties of the SPME fiber coatings). Pargyline was used as the internal standard. Extraction efficiencies for both selegiline and desmethylselegiline were 2.0–3.4% for whole blood, and 8.0–13.2% for urine. The regression equations for selegiline and desmethylselegiline extracted from whole blood were linear ( r 2 = 0.996 and 0.995) within the concentration ranges 0.1–10 and 0.2–20 ng/ml, respectively. For urine, the regression equations for selegiline and desmethylselegiline were linear ( r 2 = 0.999 and 0.998) within the concentration ranges 0.05–5.0 and 0.1–10 ng/ml, respectively. The limit of detection for selegiline and desmethylselegiline was 0.01–0.05 ng/ml for both samples. The lower and upper limits of quantification for each compound were 0.05–0.2 and 5–20 ng/ml, respectively. Intra- and inter-day coefficients of variation for selegiline and desmethylselegiline in both samples were not greater than 8.7 and 11.7%, respectively. The determination of selegiline and desmethylselegiline concentrations in Parkinson's disease patients undergoing continuous selegiline treatment is presented and is shown to validate the present methodology.

Development of a simple and sensitive method for the characterization of odorous waste gas emissions by means of solid-phase microextraction (SPME) and GC–MS/olfactometry

A solid-phase microextraction (SPME) method has been developed for the extraction of odorous compounds from waste gas. The enriched compounds were characterized by gas chromatography–mass spectrometry (GC–MS) and gas chromatography followed by simultaneous flame ionization detection and olfactometry (GC–FID/O). Five different SPME fiber coatings were tested, and the carboxen/polydimethylsiloxane (CAR/PDMS) fiber showed the highest ability to extract odorous compounds from the waste gas. Furthermore, parameters such as exposure time, desorption temperature, and desorption time have been optimized. The SPME method was successfully used to characterize an odorous waste gas from a fat refinery prior to and after waste gas treatment in order to describe the treatment efficiency of the used laboratory scale plant which consisted of a bioscrubber/biofilter combination and an activated carbon adsorber. The developed method is a valuable approach to provide detailed information of waste gas composition and complements existing methods for the determination of odors. However, caution should be exercised if CAR/PDMS fibers are used for the quantification of odorous compounds in multi-component matrices like waste gas emissions since the relative affinity of each analyte was shown to differ according to the total amount of analytes present in the sample.

Solid phase microextraction for the determination of chromium in sea-water

Application of solid phase microextraction (SPME) to the extraction of Cr from sea-water after derivatization with the β-diketonate ligand 1,1,1-trifluoro-2,4-pentadione (trifluoroacetylacetone) is reported. The chelation reaction was conducted in a single (aqueous) phase medium. Both liquid phase and headspace extraction were studied by employing a 100 µm PDMS (polydimethylsiloxane) coated SPME fiber. Capillary gas chromatography (GC) coupled to electron capture detection (ECD), electron impact-mass spectrometry (EI-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) were compared for the quantitation of Cr. Except for the ECD, isotope dilution calibration was applied, using 53Cr enriched spikes. Detection limits between 0.011–0.015 ng ml−1 (as Cr) were achieved with all three systems. Accuracy was assessed using CASS-4 Nearshore Seawater Certified Reference Material (CRM) from the National Research Council of Canada (NRCC). The developed method provided accurate results with EI-MS and ICP-MS detection, while significant bias was experienced with the ECD.

Determination of amphetamines in human urine by headspace solid-phase microextraction and gas chromatography

Solid-phase microextraction (SPME) is under investigation for its usefulness in the determination of a widening variety of volatile and semivolatile analytes in biological fluids and materials. Semivolatiles are increasingly under study as analytical targets, and difficulties with small partition coefficients and long equilibration times have been identified. Amphetamines were selected as semivolatiles exhibiting these limitations and methods to optimize their determination were investigated. A 100-μm polydimethylsiloxane (PDMS)-coated SPME fiber was used for the extraction of the amphetamines from human urine. Amphetamine determination was made using gas chromatography (GC) with flame-ionization detection (FID). Temperature, time and salt saturation were optimized to obtain consistent extraction. A simple procedure for the analysis of amphetamine (AMP) and methamphetamine (MA) in urine was developed and another for 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy- N-methamphetamine (MDMA) and 3,4-methylenedioxy- N-ethylamphetamine (MDEA) using headspace solid-phase microextraction (HS-SPME) and GC–FID. Higher recoveries were obtained for amphetamine (19.5–47%) and methamphetamine (20–38.1%) than MDA (5.1–6.6%), MDMA (7–9.6%) and MDEA (5.4–9.6%).

Validation of an SPME method, using PDMS, PA, PDMS-DVB, and CW-DVB SPME fiber coatings, for analysis of organophosphorus insecticides in natural waters.

Solid-phase microextraction (SPME) has been optimized and applied to the determination of the organophosphorus insecticides diazinon, dichlofenthion, parathion methyl, malathion, fenitrothion, fenthion, parathion ethyl, bromophos methyl, bromophos ethyl, and ethion in natural waters. Four types of SPME fiber coated with different stationary phases (PDMS, PA, PDMS-DVB, and CW-DVB) were used to examine their extraction efficiencies for the compounds tested. Conditions that might affect the SPME procedure, such as extraction time and salt content, were investigated to determine the analytical performance of these fiber coatings for organophosphorus insecticides. The optimized procedure was applied to natural waters - tap, sea, river, and lake water - spiked in the concentration range 0.5 to 50 micro g L(-1) to obtain the analytical characteristics. Recoveries were relatively high - >80% for all types of aqueous sample matrix - and the calibration plots were reproducible and linear (R(2)>0.982) for all analytes with all the fibers tested. The limits of detection ranged from 2 to 90 ng L(-1), depending on the detector and the compound investigated, with relative standard deviations in the range 3-15% at all the concentration levels tested. The SPME partition coefficients (K(f)) of the organophosphorus insecticides were calculated experimentally for all the polymer coatings. The effect of organic matter such as humic acids on extraction efficiency was also studied. The analytical performance of the SPME procedure using all the fibers in the tested natural waters proved effective for the compounds.

Optimization of extraction conditions for low-molecular-weight analytes using solid-phase microextraction

A group of volatile analytes under a molecular weight of 90 and representing 11 organic classes are extracted using identical conditions with 6 different solid-phase microextraction fiber coatings. The amount of each of the analytes extracted by the various fibers is shown. The effects of sample modifiers, such as pH and ionic strength, on the recovery of the analytes are presented. A comparison of headspace and immersion extraction techniques is shown.

Analysis of selected gaseous organic micro-pollutants in air by means of solid phase microextraction-gas chromatography-mass spectrometry. Calibration problems

In this work, problems related to calibr ation of solid phase microextraction (SPME) device were described . The ef fects of humidity and temperature on organic pollutants sampling from gaseous matrices on a 100 µm PDMS coated SPME fiber were studied. Standard gaseous mixtures used in these studies were gener ated by the permeation method and humidified to known lev- els of relati ve humidity. The SPME-GC-MS based procedure was used to determine organic vapours (carbon tetrachloride , toluene, chlorobenzene, p-xylene and n-decane) in a laboratory air. Key wo rd s. Solid phase micro ex t raction — gas c h ro m at ograp hy — calibration — v o l atile organic air pollutants — mass spectrometry.