Solid-phase Microextraction Sampling Research Articles

System Design for Integrated Comprehensive and Multidimensional Gas Chromatography with Mass Spectrometry and Olfactometry

An integrated system having the combined capability to perform gas chromatography (GC), comprehensive two-dimensional GC (GC × GC), and target heart-cut multidimensional GC (MDGC) using olfactometry (O), flame ionization (FID), and/or mass spectrometry (MS) detection is described. This combines a number of contemporary GC methods into a single instrument to provide very high resolution profiling of a sample. This provides initial assessment of volatile compound composition through GC × GC analysis with FID, which can be correlated with GC analysis using parallel O and FID detection. Subsequent microfluidic (Deans) switching selects regions (heart-cuts) of the chromatographic elution from the first dimension ((1)D) column for further resolution on a long second dimension ((2)D(L)) column for parallel detection of O and MS. Various (2)D(L) operational conditions, as well as the effect of different heart-cut (H/C) duration, were compared. The favored mode involves cryotrapping of heart-cuts, cooling the oven, and reducing carrier flow to offer greater efficiency. An analytical strategy that incorporates GC-FID/O, GC × GC-FID, and MDGC-MS/O analyses with cumulative solid phase microextraction (SPME) sampling for volatile sample enrichment is presented in this work. Excellent qualitative and quantitative performance was demonstrated with a Shiraz wine sample and an allergens mixture, with tentative identification of acetic acid, octen-3-ol, and ethyl octanoate as aroma contributors in Shiraz wine and determination of β-damascenone (floral odor) well separated from hexanoic acid (sweaty odor). A novel approach to obtain (2)D retention indices is reported, allowing matching of mass spectral, (1)I (retention index in (1)D) and (2)I (retention index in (2)D) data. The method employs the same olfactory detector at the end of the (1)D and (2)D(L) columns.

Essential oils and their compositions as spatial repellents for pestiferous social wasps

The study objectives were: (1) to field test potential repellency of common essential oils against several pestiferous social wasps (Hymenoptera: Vespidae), using attractant-baited traps; (2) to identify vespid antennally active compounds from the repellent essential oils; (3) to determine potential repellency of these electroantennographic detection (EAD) active compounds in the field. Of the 21 essential oils tested, 17 showed significant repellency on yellowjackets [mainly Vespula pensylvanica (Saussure)] and paper wasps [mainly Polistes dominulus (Christ)]: clove, pennyroyal, lemongrass, ylang ylang, spearmint, wintergreen, sage, rosemary, lavender, geranium, patchouli, citronella, Roman chamomile, thyme, fennel seed, anise and peppermint. Two essential oil mixtures - 3EO-mix (clove, geranium and lemongrass) and 4EO-mix (clove, geranium, lemongrass and rosemary) - totally blocked the attraction of vespid workers. Twenty-nine vespid antennally active compounds were identified from solid-phase microextraction (SPME) samples of 11 strongly repellent essential oils by GC-EAD/MS techniques. Among the synthetic EAD-active compounds field tested, eugenol, P/I-menthone, pulegone, α/β-thujone, l-carvone, E/Z-citral, citronellal, methyl benzoate, benzyl acetate, methyl salicylate and 3-octanol showed a significant repellency on vespid workers. These compounds are likely responsible for the repellency of their corresponding essential oils. These repellent essential oils and their active compositions have great potential for efficient, environmentally sound semiochemical-based IPM of pestiferous vespid wasps.

SPME-based air sampling method for inhalation exposure assessment studies: case study on perchlorethylene exposure in dry cleaning

Exposure to perchlorethylene, especially for dry cleaning workers and for people living near dry cleaning shops, could lead to several diseases and disorders. This study examines the value of solid-phase microextraction (SPME) for sampling perchlorethylene in the atmosphere of dry cleaning shops. Carboxen/polydimethylsiloxane (CAR/PDMS) in 0.5-cm retracted mode was selected. There were no significant differences between sampling rates at different temperatures (range of 20 to 30 °C) and air velocities (2 to 50 cm/s). On the opposite, relative humidity (RH) had a significant effect on sampling rates. Method reproducibility was realized in the laboratory and field conditions and was 6.2 % and 7 to 11 %, respectively. Repeatability was also determined as 8.9 %. Comparison of the results according to the American Industrial Hygiene Association exposure assessment strategy showed the SPME sampler yields more conservative results in comparison with traditional standard method.

Characterization of volatile composition of Laurencia dendroidea by gas chromatography-mass spectrometry

In this study we report the characterization of the volatile compounds of Laurencia dendroidea. Solvent extracts (dichloromethane and methanol), hydrodistillation extracts and headspace solid-phase microextraction samples were obtained and analyzed by GC-MS. Forty-six volatile components were identified in L. dendroidea, among them hydrocarbons, alcohols, phenols, aldehydes, ketones, acids, esters and terpenes.

Selected ion storage versus tandem MS/MS for organochlorine pesticides determination in drinking waters with SPME and GC-MS

The use of two modes for mass spectrometry (MS) detection with an ion trap instrument, selected ion storage (SIS) and tandem mass spectrometry (MS/MS), are compared for the solid-phase microextraction (SPME)–gas chromatography (GC) coupled to mass spectrometry (GC-MS) determination of 16 priority organochlorine pesticides (OCPs) in drinking water samples at the ultratrace levels (ng L−1) required by official guidelines in the European legislation. Experimental parameters investigated for the SPME sample preparation were: the type of coating (100 µm polydimethylsiloxane, PDMS, and 65 µm poly(dimethylsiloxane)–divinylbenzene, PDMS/DVB), SPME modality, extraction and desorption times and desorption temperature and the methanol percentage in the SPME working solution. Under the calculated optimal conditions two methodologies were developed, one for SIS and the other for MS/MS modes. The detection limits, precision and accuracy were evaluated for both alternatives and were appropriate to the official guidelines requirements. The SPME–GC-MS(SIS) methodology offered LODs from 0.2–6.6 ng L−1, precision below 13% and recoveries between 83 and 110%. The SPME–GC–MS/MS methodology provided limits of detection (LODs) ranging from 0.3 to 7.6 ng L−1, % RSD were ≤14% and recoveries of 79–108% were achieved. After the results observed within an Interlaboratory Exercise, the latest MS methodology was selected for the pursued analysis in real drinking water samples. Also, the good results in this round-robin exercise validate the proposed SPME–GC–MS/MS methodology.

Effect of Henry's law constant and operating parameters on vacuum-assisted headspace solid phase microextraction

Nonequilibrium headspace solid-phase microextraction (HSSPME) sampling under vacuum conditions may dramatically improve extraction kinetics compared to regular HSSPME at room temperature. This paper investigates the effects of organic analyte properties and sampling parameters (headspace volume and sample agitation) on vacuum-assisted HSSPME (Vac-HSSPME). It was found that at room temperature, acceleration effects on extraction rates induced by reducing the total pressure of the sample container are important for those compounds where the Henry's law constant, KH, is close or below the reported threshold values for low KH solutes. For these compounds evaporation rate is controlled by mass transfer resistance in the thin gas-film adjacent to the gas/sample interface and reducing the total pressure will increase evaporation rates and result in a faster overall extraction process. Conversely, for analytes with an intermediate KH value, Vac-HSSPME is not expected to improve extraction rates compared to regular HSSPME given that mass transfer resistance in the liquid-film becomes important. In accordance with the theory, at equilibrium, the amount of analyte extracted by the SPME fiber is not affected by the pressure conditions inside the sample container. Furthermore, Vac-HSSPME extraction kinetics for low KH analytes were marginally affected by the tested change in headspace volume as evaporation rates dramatically increase under reduced pressure conditions and the sample responds much faster to the concentration drops in the headspace when compared to regular HSSPME. At equilibrium however, increasing the headspace volume may result in a loss of sensitivity for Vac-HSSPME similar to that observed for regular HSSPME. As expected, stirring the liquid sample was found to improve Vac-HSSPME. Finally, the method yielded a linearity of 0.998 and detection limits in the ppt level. The precision varied between 1.8% and 8.4%.

New method to determination of naphthalene in ambient air using cold fiber-solid phase microextraction and gas chromatography–mass spectrometry

Naphthalene, a highly volatile polycyclic aromatic hydrocarbon (PAH), is classified as possibly carcinogenic to humans and can be found in various environments. This paper describes a cold fiber (CF) solid phase microextraction (SPME) sampling method coupled with gas chromatography/mass spectrometry (GC/MS) for determining naphthalene in ambient air. The method uses a 100μm polydimethylsiloxane (PDMS) fiber to generate gaseous standards using a permeation tube. The method shows good results for many validation parameters. The intra-assay precision shows a relative standard deviation (RSD) ranging from 1.04 to 8.11%; the limit of detection (LOD) is 0.33±0.01μg/m3, and the quantification limit (LOQ) is 0.55±0.01μg/m3. The method was applied to the determination of naphthalene from real samples collected from indoor and outdoor air. The results have shown the ability of the method to measure trace levels of naphthalene in the air in different environments.

Cumulative solid phase microextraction sampling for gas chromatography-olfactometry of Shiraz wine

Solid phase microextraction (SPME) coupled to gas chromatography-olfactometry (GC-O) is now commonly used for determination of aroma-active compounds, but the method sensitivity and selectivity is restricted by the small volume and limited type of fibre coating phases. In an attempt to enhance the method performance, a cryogenic trapping (CT) approach was investigated in this study by coupling multiple SPME sampling events for wine headspace using GC-O analysis. By performing multiple SPME sampling employing different chemical polymer coatings, desorbed solute from the integrated sampling is accumulated by the CT at the front section of a Wax separation capillary column prior to chromatographic analysis. Results show that the CT was capable of retaining apolar alkane volatiles of decane and greater, and tested polar alcohols, including methanol. Chromatographic signals eluting later than the ethanol peak were found to progressively increase in response, and correlated well, with the cumulative number of SPME samplings. The approach was developed for GC-O screening of potent odorants in Shiraz wine collected from fibre coatings of polyacrylate (PA) and the triple-phase coated polydimethylsiloxane/divinylbenzene/carboxen (PDC). The aromagram for solute derived from a combined introduction of both PA plus PDC fibres (i.e. sequential fibre introduction into the injector; termed as PADC) compared well to the sum of those sampled by using a single fibre coating alone, which comprised of odorants derived from both fibre coatings. Accumulation in the CT of volatile solutes derived from up to 6 repeat PADC sampling events revealed a similar pattern of their aromagrams, though with stronger olfactory stimulus response. This study demonstrated a simple and effective way for enhancing SPME sensitivity and potentially less discrimination during the analysis of wine volatiles. However, the single dimensional GC separation method requires development of an improved separation strategy to better separate individual compounds.

ChemInform Abstract: Chemical Techniques for Assessing Bioavailability of Sediment‐Associated Contaminants — SPME Versus Tenax Extraction

AbstractReview: 66 refs.

Estimation of resistance of starch/polyvinyl alcohol blends to permeation by organic solvents

The chemical resistance of chlorinated hydrocarbons in starch/polyvinyl alcohol (PVA) blends has been investigated using a permeation cell with an in-cell solid phase microextraction (SPME) sampling device. The chlorinated hydrocarbon with a large molecule size or lower polarity was found to be less permeable through the starch/PVA blends. The tensile strength and chemical resistance of chlorinated hydrocarbons decreased with an increase in the starch content of blends. For the starch/PVA blends, the solubility of chlorinated hydrocarbons was inversely proportional to their molecular weight, molar volume and log Kow. The diffusion coefficients and solubility of permeants were proportional to the content of starch in the starch/PVA blends. It is plausible that the blends will be inclined to the starch characteristics as the plasticizer (i.e. glycerin) disrupts the rigidity arrangements of the starch and PVA. The present work provides information on the extent of organic compound permeation through starch/PVA blends for the practical application.

Determination of Inhalational Anesthetics in Field and Laboratory by SPME GC/MS

Exposure to inhalational anesthetics in health care workers could lead to several diseases and disorders. This study examined the applicability of solid phase microextraction for sampling and quantification of three inhalational anesthetics including; halothane, isoflurane, and sevoflurane in operating room air. Carboxen-Polydimethylsiloxane in retracted mode was selected and the effects of environmental parameters including temperature, humidity, and air velocity, were studied. There were no significant differences between sampling rates determined at different temperatures and air velocities. On the opposite, relative humidity has a significant effect on sampling rates. Comparison of the results between the developed SPME method and OSHA 103 method on standard test atmosphere and field showed satisfactory agreement.

Time-Weighted Average SPME Analysis for in Planta Determination of cVOCs

The potential of phytoscreening for plume delineation at contaminated sites has promoted interest in innovative, sensitive contaminant sampling techniques. Solid-phase microextraction (SPME) methods have been developed, offering quick, undemanding, noninvasive sampling without the use of solvents. In this study, time-weighted average SPME (TWA-SPME) sampling was evaluated for in planta quantification of chlorinated solvents. TWA-SPME was found to have increased sensitivity over headspace and equilibrium SPME sampling. Using a variety of chlorinated solvents and a polydimethylsiloxane/carboxen (PDMS/CAR) SPME fiber, most compounds exhibited near linear or linear uptake over the sampling period. Smaller, less hydrophobic compounds exhibited more nonlinearity than larger, more hydrophobic molecules. Using a specifically designed in planta sampler, field sampling was conducted at a site contaminated with chlorinated solvents. Sampling with TWA-SPME produced instrument responses ranging from 5 to over 200 times higher than headspace tree core sampling. This work demonstrates that TWA-SPME can be used for in planta detection of a broad range of chlorinated solvents and methods can likely be applied to other volatile and semivolatile organic compounds.

Volatilizable Biogenic Organic Compounds (VBOCs) with two dimensional Gas Chromatography-Time of Flight Mass Spectrometry (GC <b>×</b> GC-TOFMS): sampling methods, VBOC complexity, and chromatographic retention data

Abstract. Two dimensional gas chromatography (GC × GC) with detection by time-of-flight mass spectrometry (TOFMS) was applied in the rapid analysis of air samples containing highly complex mixtures of volatilizable biogenic organic compounds (VBOCs). VBOC analytical methodologies are briefly reviewed, and optimal conditions are discussed for sampling with both adsorption/thermal desorption (ATD) cartridges and solid-phase microextraction (SPME) fibers. Air samples containing VBOC emissions from leaves of two tree species (Cedrus atlantica and Calycolpus moritzianus) were obtained by both ATD and SPME. The optimized gas chromatographic conditions utilized a 45 m, 0.25 mm I.D. low-polarity primary column (DB-VRX, 1.4 μm film) and a 1.5 m, 0.25 mm I.D. polar secondary column (StabilwaxTM, 0.25 μm film). Excellent separation was achieved in a 36 min temperature programmed GC × GC chromatogram. Thousands of VBOC peaks were present in the sample chromatograms; hundreds of tentative identifications by NIST mass spectral matching are provided. Very few of the tentatively identified compounds are currently available as authentic standards. Minimum detection limit values for a 5 l ATD sample were 3.5 pptv (10 ng m−3) for isoprene, methyl vinyl ketone, and methacrolein, and ~1.5 pptv (~10 ng m−3) for monoterpenes and sesquiterpenes. Kovats-type chromatographic retention index values on the primary column and relative retention time values on the secondary column are provided for 21 standard compounds and for 417 tentatively identified VBOCs. 19 of the 21 authentic standard compounds were found in one of the Cedrus atlantica SPME samples. In addition, easily quantifiable levels of at least 13 sesquiterpenes were found in an ATD sample obtained from a branch enclosure of Calycolpus moritzianus. Overall, the results obtained via GC × GC-TOFMS highlight an extreme, and largely uncharacterized diversity of VBOCs, consistent with the hypothesis that sesquiterpenes and other compounds beyond the current list of typically determined VBOC analytes may well be important contributors to global atmospheric levels of organic particulate matter.

Semi-automated in vivo solid-phase microextraction sampling and the diffusion-based interface calibration model to determine the pharmacokinetics of methoxyfenoterol and fenoterol in rats

In vivo solid-phase microextraction (SPME) can be used to sample the circulating blood of animals without the need to withdraw a representative blood sample. In this study, in vivo SPME in combination with liquid–chromatography tandem mass spectrometry (LC–MS/MS) was used to determine the pharmacokinetics of two drug analytes, R,R-fenoterol and R,R-methoxyfenoterol, administered as 5mgkg−1i.v. bolus doses to groups of 5 rats. This research illustrates, for the first time, the feasibility of the diffusion-based calibration interface model for in vivo SPME studies. To provide a constant sampling rate as required for the diffusion-based interface model, partial automation of the SPME sampling of the analytes from the circulating blood was accomplished using an automated blood sampling system. The use of the blood sampling system allowed automation of all SPME sampling steps in vivo, except for the insertion and removal of the SPME probe from the sampling interface. The results from in vivo SPME were compared to the conventional method based on blood withdrawal and sample clean up by plasma protein precipitation. Both whole blood and plasma concentrations were determined by the conventional method. The concentrations of methoxyfenoterol and fenoterol obtained by SPME generally concur with the whole blood concentrations determined by the conventional method indicating the utility of the proposed method. The proposed diffusion-based interface model has several advantages over other kinetic calibration models for in vivo SPME sampling including (i) it does not require the addition of a standard into the sample matrix during in vivo studies, (ii) it is simple and rapid and eliminates the need to pre-load appropriate standard onto the SPME extraction phase and (iii) the calibration constant for SPME can be calculated based on the diffusion coefficient, extraction time, fiber length and radius, and size of the boundary layer. In the current study, the experimental calibration constants of 338.9±30mm−3 and 298.5±25mm−3 are in excellent agreement with the theoretical calibration constants of 307.9mm−3 and 316.0mm−3 for fenoterol and methoxyfenoterol respectively.

SPME法分析玉米芯物理吸附恶臭气体特征研究

SPME法分析玉米芯物理吸附恶臭气体特征研究

Profiling and characterization of volatile secretions from the European stink bug Graphosoma lineatum (Heteroptera: Pentatomidae) by two-dimensional gas chromatography/time-of-flight mass spectrometry

An efficient method combining the headspace solid-phase microextraction (HS-SPME) sampling procedure and comprehensive two-dimensional gas-chromatography/time-of-flight mass spectrometry (GC × GC/TOF-MS) was established to study the volatile secretion components of stink bugs (Heteroptera: Pentatomidae). The combined power of this approach is illustrated by the identification of fifty-seven compounds in the secretion of a European stink-bug representative, Graphosoma lineatum. ( E)-4-oxohex-2-enal and ( E)-dec-2-enal were found to be the major components in the adult bug secretions followed by lower amounts of n-alkenal (C 5–C 12), n-alkenyl acetate (C 5–C 11), n-alkane (C 11–C 17) homologs, dienals and other compounds. More than thirty known compounds have been identified that had not been described before in G. lineatum adults. Of these compounds, ( E)-4-oxohex-2-enal is of particular interest, since its isolation and identification, while calling some previous reports into question, clearly demonstrates a potential ability of our approach to yield artifact-free secretion profiles.

Measuring Local Equilibrium Flavor Distributions in SDS Solution Using Headspace Solid-Phase Microextraction

Solid-phase microextraction (SPME) sampling of the headspace above an aqueous micellar solution of sodium dodecyl sulfate (SDS) was shown to be effective for quantifying the equilibrium partitioning of limonene solute between water and SDS micellar aggregates. Concentrations in the headspace were determined from the amount absorbed by the SPME fiber during 1 min extractions, with the quantity on the fiber determined using gas chromatography/mass spectrometry (GC/MS). Headspace concentrations as a function of surfactant concentration were fit to a mass balance to yield the partition coefficient and critical micelle concentration. When the total limonene in the system was low enough that it could be completely dissolved by water in the absence of micelles, a constant value for the partition coefficient of 1700 M(-1) was obtained, independent of the limonene concentration. However, at higher total limonene concentrations, the partition coefficient became a function of the amount of limonene in the micelles, as confirmed by separate experiments in which either limonene or SDS concentration was varied. The observed increase in partition coefficient with increasing limonene likely signals a shift from micelles to swollen micelles and ultimately to microemulsion droplets. The effect of SDS concentration on the aqueous solubility limit of limonene could also be observed in HS-SPME experiments where either SDS or limonene was varied.

Development of an in-cell SPME method to determine the chemical resistance of polymeric membranes to permeation by organic solvents

A stainless steel cell with an in-cell solid-phase microextraction (SPME) sampling device is proposed to investigate the permeation of dichloromethane, 1,2-dichloroethane, and benzene through a high-density polyethylene (HDPE) membrane. The advantage of using SPME as a direct sampling device in the collection chamber is that it is a simple and sensitive means to monitor the concentrations of organic compounds in the collection medium for a closed-loop test system. Compared with the permeation results for an ASTM F739 cell, the standardized breakthrough times were shorter and the permeability coefficients were greater using the alternative cell. Although the optimum SPME sampling parameters should be obtained in advance, the in-cell SPME method can be an appropriate approach to determine the resistance of polymeric membranes to permeation by organic solvents.

Pre-Equilibrium Solid-Phase Microextraction of Free Analyte in Complex Samples: Correction for Mass Transfer Variation from Protein Binding and Matrix Tortuosity

The accurate measurement of free analyte concentrations within complex sample matrixes by pre-equilibrium solid-phase microextraction (SPME) has proven challenging due to variations in mass uptake kinetics. For the first time, the effects of the sample binding matrix and tortuosity on the kinetics of analyte extraction (from the sample to the SPME fiber) are demonstrated to be quantitatively symmetrical with those of the desorption of preloaded deuterated standards (from the fiber to the sample matrix). Consequently, kinetic calibration methods can be employed to correct for variation in SPME sampling kinetics, facilitating the application of pre-equilibrium SPME within complex sample systems. This approach was applied ex vivo to measure pharmaceuticals in fish muscle tissues, with results consistent with those obtained from equilibrium SPME and microdialysis. The developed method has the inherent advantages of being more accurate, precise, and reproducible, thus providing the framework for applications where rapid measurement of free analyte concentrations (within complicated sample matrixes such as biological tissues, sediment, and surface water) are required.

Identification of Components of the Female Sex Pheromone of the Simao Pine Caterpillar Moth, Dendrolimus kikuchii Matsumura

The pine caterpillar moth, Dendrolimus kikuchii Matsumura (Lepidoptera: Lasiocampidae), is a pest of economic importance on pine in southwest China. Three active compounds were detected during analyses of solvent extracts and effluvia sampled by solid phase microextraction (SPME) from virgin female D. kikuchii using gas chromatography (GC) coupled with electroantennographic (EAG) recording with antennae from a male moth. The compounds were identified as (5Z,7E)-5,7-dodecadien-1-yl acetate (Z5,E7-12:OAc), (5Z,7E)-5,7-dodecadien-1-ol (Z5,E7-12:OH), and (5Z)-5-dodecenyl acetate (Z5-12:OAc) by comparison of their GC retention indices, mass spectra, and EAG activities with those of synthetic standards. Microchemical reactions of gland extracts provided further information confirming the identifications of the three components. Solvent extractions and SPME samples of pheromone effluvia from virgin calling females provided 100:18:0.6 and 100:7:1 ratios of Z5,E7-12:OAc:Z5,E7-12:OH:Z5-12:OAc, respectively. Field behavioral assays showed that Z5,E7-12:OAc and Z5,E7-12:OH were essential for attraction of male D. kikuchii moths. However, the most attractive blend contained these three components in a 100:20:25 ratio in a gray rubber septa. Our results demonstrated that the blend of Z5,E7-12:OAc, Z5,E7-12:OH, and Z5-12:OAc comprise the sex pheromone of D. kikuchii. The optimized three-component lure blend is recommended for monitoring D. kikuchii infestations.