SEARCH · PubMed Health

Results for “Solid Phase Microextraction”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources

PubMed2003

Evaluation of Kd underestimation using solid phase microextraction.

Many important environmental pollutants are strongly adsorbing hydrophobic compounds. Because of their potential to adsorb to dissolved organic matter (DOM), their partition coefficient Kd may be underestimated by the conventional approach due to incomplete phase separation. In this study, solid-phase microextraction (SPME) was compared with liquid-liquid partition (LLP) for measuring Kd of bifenthrin and permethrin isomers on sediments. Due to its selective detection of the freely dissolved concentration, SPME gave Kd values 0.6-4.4-fold greater than those obtained by LLP in creek and field sediments and 3.6-21.7-fold greater in nursery runoff sediments. Underestimation by the conventional method was attributed to adsorption to DOM that was not excluded from the aqueous phase by centrifugation. The degree of underestimation was dependent on the source and amount of DOM and may be generally significant for compounds that have DOM adsorption coefficient (KDOM) > 10(4). This study provides evidence that the existing Kd values for many hydrophobic pollutants may be underestimated, and SPME may be a viable, efficacious tool for evaluating the underestimation.

Adsorption↗

PubMed2004

Headspace solid-phase microextraction with gas chromatography and mass spectrometry in the investigation of volatile organic compounds in an ectomycorrhizae synthesis system.

Ectomycorrhizae formation represents one of the most significant steps in the truffle life cycle and is determined by a complex molecular signaling between two symbionts. In order to understand the molecular pathway of ectomycorrhiza development, we focused on the signaling interaction between the ectomycorrhizal fungus Tuber borchii Vittad. and the Tilia americana L. plant roots. The medium of a pre-symbiotic (T. americana-T. borchii) in vitro system was analysed by headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry. In total, 73 volatile organic compounds (VOCs) were identified. Twenty-nine of these VOCs were produced only during the interaction phase between the two partners, leading to a hypothesis that these molecules might act as molecular messengers in order to pilot the ectomycorrhizae formation.

Gas Chromatography-Mass Spectrometry↗

PubMed2002

Quantitation of 2-chlorovinylarsonous acid in human urine by automated solid-phase microextraction--gas chromatography--mass spectrometry.

Lewisite [dichloro(2-chlorovinyl)arsine] is a highly toxic chemical warfare agent with vesicant properties. The accidental exposure to lewisite or its intentional use as a chemical terrorism weapon are a public health threat and warrant investigations for the development of analytical methods to detect biomarkers of exposure to lewisite. Under aqueous conditions, lewisite rapidly hydrolyzes to the non-volatile 2-chlorovinylarsonous acid (CVAA). We have developed a sensitive, simple, and automated method for measuring CVAA in human urine. The assay is based on the use of solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) after derivatization of the CVAA with 1,3-propanedithiol (PDT). The volatile CVAA-PDT is adsorbed onto a SPME fiber and analyzed by GC-MS. The assay was validated on human urine samples spiked with CVAA to determine the accuracy, precision, and limit of detection (LOD). The LOD was 7.4 pg in 1 ml of urine.

Arsenicals↗

PubMed2002

Semiquantitative determination of off-notes in mint oils by solid-phase microextraction.

Mint essential oils are produced by the steam distillation of dried or partially dried harvested plant material. In the United States, harvesting is done mechanically so that any weeds found in the field are concomitantly harvested. Steam distillation of contaminated plant material leads to off-notes in the oil, which are currently determined by a sensory panel. Furthermore, nonoptimized distillation conditions can lead to the thermal degradation of carbohydrates and proteins resulting also in the formation of very volatile off top-notes. As a result, the use of a nonequilibrated solid-phase microextraction (SPME) procedure to determine the off-notes is evaluated. The results of this evaluation include a combination of semiquantitative data, odor threshold data, and mathematical data manipulation to ascertain the capabilities of a SPME approach. The results are correlated with sensory panel data to yield a relatively rapid analytical methodology that can be used either in place of or in support of sensory analyses. The main advantage of the technique described is to provide some semiquantitative data in support of the odor-panel screening of mint oils for off-notes. Based on the data presented in this report, it is believed that this has been successfully demonstrated.

Gas Chromatography-Mass Spectrometry↗

PubMedDate not supplied

Quantification of dichloroiodomethane and bromochloroiodomethane in human blood by solid-phase microextraction coupled with gas chromatography-high-resolution mass spectrometry.

Iodine-containing trihalomethanes (iodo-THMs) are formed as disinfection byproducts when iodide-containing water is disinfected using chloramination process. Subsequent water use may lead to human exposure to iodo-THMs. Because of health concerns surrounding exposure to iodo-THMs, a rapid, reliable, and high-throughput analytical method was developed to quantify trace levels of two iodo-THMs: dichloroiodomethane (IDCM) and bromochloroiodomethane (IBCM) in human blood. These analytes from the headspace above blood samples were extracted using solid-phase microextraction. Analytes were then desorbed and separated by capillary gas chromatography and analyzed by high-resolution mass spectrometry with multiple ion monitoring. This method utilizes stable isotope dilution to quantify parts-per-trillion levels of all analytes, with excellent precision of < 9% coefficient of variation. At three spiked levels, method accuracy of IDCM and IBCM ranged between 6 and 20% difference when comparing spiked and measured amounts. The method limit of detection was 2 ng/L for both IDCM and IBCM. This selective, sensitive, and rapid method will help to assess human exposure to iodo-THMs and to study potential associations between exposure and adverse health outcomes.

Adult↗

PubMed2005

Analysis of gamma-hydroxybutyric acid (GHB) in spiked water and beverage samples using solid phase microextraction (SPME) on fiber derivatization/gas chromatography-mass spectrometry (GC/MS).

Gamma-Hydroxybutyric acid (GHB) is a CNS depressant that has been abused recreationally for its purported euphoric and relaxation effects and for the purposes of drug facilitated sexual assault due to its sedative and amnesic effects at higher doses. The dramatic increase in the abuse of GHB and association in criminal investigations over the past decade has created the need for forensic laboratories to develop analytical methods to detect GHB in a variety of matrices. The method developed in this work used solid-phase microextraction (SPME) to extract GHB from aqueous samples followed by on-fiber derivatization and analysis by gas chromatography/mass spectrometry (GC/MS). This method detected GHB in aqueous matrices with good sensitivity, high precision, excellent linearity from 0.01 mg/mL to 0.25 mg/mL, and without the need for sample manipulation that could cause interconversion between GHB and its lactone, GBL. The method was successfully applied for detection of GHB in spiked water and beverage samples.

Beverages↗

PubMed2006

Solid-phase microextraction as a novel air sampling technology for improved, GC-olfactometry-based assessment of livestock odors.

Air sampling and characterization of odorous livestock gases is one of the most challenging analytical tasks. This is because of low concentrations, physicochemical properties, and problems with sample recoveries for typical odorants. Livestock operations emit a very complex mixture of volatile organic compounds (VOCs) and other gases. Many of these gases are odorous. Relatively little is known about the link between characteristic VOCs/gases and, specifically, about the impact of characteristic odorants downwind from sources. In this research, solid-phase microextraction (SPME) is used for field air sampling of odors downwind from swine and beef cattle operations. Sampling time ranges from 20 min to 1 h. Samples are analyzed using a commercial gas chromatography-mass spectrometry-olfactometry system. Odor profiling efforts are directed at odorant prioritization, with respect to distance from the source. The results indicate the odor downwind is increasingly defined by a smaller number of high-priority odorants. These "character defining" odorants appear to be dominated by compounds of relatively low volatility, high molecular weight, and high polarity. In particular, p-cresol alone appears to carry much of the overall odor impact for swine and beef cattle operations. Of particular interest is the character-defining odor impact of p-cresol as far as 16 km downwind of the nearest beef cattle feedlot. The findings are highly relevant to scientists and engineers working on improved air sampling and analysis protocols and on improved technologies for odor abatement. More research evaluating the use of p-cresol and a few other key odorants as a surrogate for overall odor dispersion modeling is warranted.

Animals↗

PubMed2003

Solid-phase microextraction and gas chromatography olfactometry analysis of successively diluted samples. A new approach of the aroma extract dilution analysis applied to the characterization of wine aroma.

The relationship between the composition and the aroma of the wine can be established by using gas chromatography with olfactometric detection (sniffing or GCO), which combines the chromatographic response with the human nose response. To evaluate the contribution of the odor compounds in wine aroma, we designed a new approach of the aroma extract dilution analysis (AEDA) that lies in the GCO analysis of serially diluted wine samples using headspace solid-phase microextraction (HS-SPME) as the extraction technique. The fiber coating used was Flex divinyl-carboxen-polydimethylsiloxane. The method developed was applied to determine the aromatic composition of a red Grenache wine from Priorat (Spain). The method allows 38 important odorants to be determined in the AEDA study, 30 of them precisely identified. These results are similar to those reported by other studies related to this variety of wine. HS-SPME is a suitable technique to obtain representative extracts of wine aroma with several advantages such as simplicity, speediness, and little sample manipulation.

Chromatography, Gas↗

PubMed2006

Determination of drug plasma protein binding by solid phase microextraction.

The plasma protein binding of drugs has been shown to have significant effects on the quantitative relationship between clinical pharmacokinetics and pharmacodynamics. In many clinical situations, measurement of the total drug concentration does not provide the needed information concerning the unbound fraction of drug in plasma, which is available for pharmacodynamic action. Therefore, the accurate determination of unbound plasma drug concentrations is important in understanding drug action. Many methodologies exist for determining the extent of plasma protein binding, but different methods produce a rather wide range of results for the same compound at the same concentration level. The solid phase microextraction (SPME) method reported in the present study attempts to eliminate many experimental variables that could lead to the lack of reproducibility, such as the variable content of organic solvent or ionic strength in plasma, pH shifts, and volume shifts. Five well-known drugs were chosen to study plasma protein binding: ibuprofen, warfarin, verapamil, propranolol, and caffeine, with high, intermediate and low binding properties. Dilution of plasma with isotonic PBS or incubation with 10% CO(2) in the atmosphere was found to compensate for changes in pH during incubation. The data obtained using these pH-controlled methods correlate well with the average values of plasma protein binding found in the literature. SPME, which uses an extraction phase that dissolves or adsorbs the drug of interest and rejects proteins, overcomes several limitations of currently available techniques and is a thermodynamically sound method, since the measurements are always performed at equilibrium. Compared to other methods, SPME offers several advantages: small sample size, short analysis time, possibility to automate, and ability to directly study complex samples.

Blood Proteins↗

PubMed2005

Simultaneous picogram determination of "earthy-musty" odorous compounds in water using solid-phase microextraction and gas chromatography-mass spectrometry coupled with initial cool programmable temperature vaporizer inlet.

"Earthy-musty" off-flavor problem in water samples are due to organic compounds present at the sub-part-per-trillion level. Most of the developments in the analysis of tastes and odorous compounds focus on the extraction pre-concentration technique, with detection at picogram per liter level of the earthy-musty off-flavor compounds difficult to be achieved. In this study, a simple, efficient and sensitive method for the analysis of odorous compounds has been developed by the application of solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) with initial cool programmable temperature vaporizer (PTV) inlet for the first time. Compared with initial hot PTV inlet, the initial cool inlet could greatly improve the system sensitivity, especially for the compounds with good volatility, e.g. 2-methylisoborneol (MIB). StableFlex divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was found to possess the best extraction efficiency towards these odorous compounds in water. Various SPME and PTV conditions have been studied and optimized in detail. The optimized method has been validated with good linearity, precision and accuracy. The method detection limits (MDL) of the targeted odorous compounds were found to be 0.32ng/L for 2,4,6-trichloroanisole (2,4,6-TCA), 0.14ng/L for 2,3,6-trichloroanisole (2,3,6-TCA), 0.16ng/L for 2,3,4-trichloroanisole (2,3,4-TCA), 0.38ng/L for 2,4,6-tribromoanisole (2,4,6-TBA), 0.16ng/L for gesomin and 0.15ng/L for MIB. To the best of our knowledge, this represents the best sensitivity achieved for analysis of gesomin and MIB in water via the simple and efficient SPME method. The current method has been successfully applied in the analyses of different water samples.

Anisoles↗

PubMed2003

On-line derivatization utilizing solid-phase microextraction (SPME) for determination of busulphan in plasma using gas chromatography-mass spectrometry (GC-MS).

Busulphan (Bu) is an alkylating agent used in preparative regimen before stem cell transplantation (SCT). Bu has a narrow therapeutic window, and underdosing or overdosing may have a fatal outcome for the patient. Therapeutic drug monitoring (TDM) combined with dose adjustment is currently used to optimize and individualize therapy with Bu. However, this approach is limited to centers with laboratory facilities. An automated and easy method for measurement of Bu plasma concentrations may facilitate TDM for Bu and thus improve the clinical outcome. A solid-phase microextraction (SPME) on line with gas chromatography (GC) and mass-spectrometric detection to quantify Bu in human plasma samples was developed using in-vial derivatization. Bu was mixed with reagent in a 2-mL vial and shaken for 15 minutes at 80 degrees C; subsequently, the SPME fiber was immersed into the vial for 15 minutes. The fiber was washed in water for 10 seconds before injection. Several parameters influencing the extraction and recovery were studied, such as absorption and desorption times, the effects of the temperature on the reaction, and the shaking time on the derivatization yield. Carbowax-divinylbenzene, polyacrylate, and polydimethylsiloxane fibers were tested. The carbowax-divinylbenzene fiber resulted in the highest recovery in plasma samples. The validation of the method showed a high chromatographic selectivity and a good sensitivity (LOQ = 20 ng/mL). Coefficient of variation for SPME was less than 15%. The results showed good correlation between Bu concentrations and response within the range of 40 to 2500 ng/mL (R2 = 0.999). The accuracy ranged from 94% to 106%. This is well in line with the international criteria for validation. The present method was applied to patient plasma. The obtained results were comparable with the results obtained from GC with electron capture detection. The authors conclude that this method has shortened the analysis time considerably and is fully automated, which benefits TDM of Bu in SCT patients.

Busulfan↗

PubMed2001

Measurement of Henry's law constant for methyl tert-butyl ether using solid-phase microextraction.

Increasing groundwater contamination with methyl tert-butyl ether (MTBE) requires more efficient remediation technologies. Accurate measurement of MTBE's air-water partitioning coefficient (Henry's law constant, H) is important for the design and optimization of removal efficiency for many treatment systems as well as for predicting its fate and transport. Previously published data for MTBE appear to have some unusual nonlinearity at lower temperatures (15-30 degrees C), and a wide range of values exists for dimensionless H at 25 degrees C, from 0.0216 to 0.1226 in the published literature. We measured H for MTBE using headspace solid-phase microextraction (SPME) and a static method that considers equilibrium partitioning in a closed system, for temperatures between 15 and 4 degrees C. To validate our methods, we measured H for benzene, toluene, and trichloroethylene and compared our results to previously published values, with excellent agreement. The Arrhenius plot for MTBE indicates that ln(HMBTE) = 6.85 - 2,900 T(-1), with T in K. At 25 degrees C, HMBTE = 0.0555 +/- 0.0122.

Carcinogens↗

PubMed2006

Development of water-phase derivatization followed by solid-phase microextraction and gas chromatography/mass spectrometry for fast determination of valproic acid in human plasma.

In this study, a simple, rapid, and sensitive method was developed and validated for the quantification of valproic acid (VPA), an antiepileptic drug, in human plasma, which was based on water-phase derivatization followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS). In the proposed method, VPA in plasma was rapidly derivatized with a mixture of isobutyl chloroformate, ethanol and pyridine under mild conditions (room temperature, aqueous medium), and the VPA ethyl ester formed was headspace-extracted and simultaneously concentrated using the SPME technique. Finally, the analyte extracted on SPME fiber was analyzed by GC/MS. The experimental parameters and method validations were studied. The optimal conditions were obtained: PDMS fiber, stirring rate of 1100 rpm, sample temperature of 80 degrees C, extraction time of 20 min, NaCl concentration of 30%. The proposed method had a limit of quantification (0.3 microg/mL), good recovery (89-97%) and precision (RSD value less than 10%). Because the proposed method combined a rapid water-phase derivatization with a fast, simple and solvent-free sample extraction and concentration technique of SPME, the sample preparation time was less than 25 min. This much shortens the whole analysis time of VPA in plasma. The validated method has been successfully used to analyze VPA in human plasma samples for application in pharmacokinetic studies. All these results show that water-phase derivatization followed by HS-SPME and GC/MS is an alternative and powerful method for fast determination of VPA in biological fluids.

Anticonvulsants↗

PubMed2004

Determination of polycyclic aromatic hydrocarbons in water by solid-phase microextraction and liquid chromatography.

This study describes the determination of polycyclic aromatic hydrocarbons (PAHs) in water using high-performance liquid chromatography (HPLC) coupled with fluorescence detection (FLD). Because individual PAHs are generally present in water only at trace levels, a sensitive and accurate determination technique is essential. The separation and detection of five PAHs were run completely within 25 min by the HPLC/FLD system with an analytical C18 column, a fluorescence detection, and acetonitrile-water gradient elution. Calibration graphs were linear with very good correlation coefficients (r > 0.9998), and the detection limits were in the range of 2-6 ng/l for five PAHs. Solid phase microextraction (SPME) was performed for sample pretreatment prior to HPLC-FLD determination, and the governing parameters were investigated. Compared to conventional methods, SPME has high recovery, saves considerable time, and reduces solvents waste. The extraction efficiencies of five PAHs were above 88% and the extraction times were 35 min in one pretreatment procedure. One particular discovery is that 1.5 M sodium monochloroactate (ClCH2COONa) can improve the extraction yield of PAH compounds more than other inorganic salts. The SPME-HPLC-FLD technique provides a relatively simple, convenient, practical procedure, which was here successfully applied to determine five PAHs in water from authentic water samples.

Chemistry Techniques, Analytical↗

PubMed2006

Ethanol/Water extraction combined with solid-phase extraction and solid-phase microextraction concentration for the determination of chlorophenols in cork stoppers.

The appearance of 2,4,6-trichloroanisole (TCA) in cork stoppers is of great concern because it can cause off-flavors in bottled wine. To prevent this sensorial defect, there should not be any traces of 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP), or pentachlorophenol (PCP) in the finished corks, because they are the direct precursors of TCA. In the course of this study two methodologies based upon an extraction with ethanol/water mixtures to determine the chlorophenolic content in cork matrices were developed. The cork extract is preconcentrated using both solid-phase extraction and solid-phase microextraction methodologies. The latter was optimized by applying a full two-level factorial design. Finally, spiked ground corks at nanogram per gram levels of each chlorophenol were analyzed under optimal conditions and by applying both procedures. The obtained results demonstrate that chlorophenols can be detected in corks contaminated at the nanogram per gram level and, thus, these approaches can be successfully applied as quality control measures in the cork industry.

Chlorophenols↗

PubMed2006

Use of multiple headspace solid-phase microextraction and pervaporation for the determination of off-flavours in wine.

The occurrence of off-flavours in wines and especially the so-called "cork taint defect" represents one of the most serious problem in wine industry in which 2,4,6-trichloroanisole has been blamed as the main responsible. The development of analytical methods for haloanisoles determination in wine/cork represent a challenge, mainly due to food matrix complexity and low taste and odour (T&O) threshold levels which are generally beyond the sensitivity of the analytical systems. In this work, a method based on the combined use of the recently developed multiple headspace solid-phase microextraction (MHS-SPME) and gas chromatography-ion-trap mass spectrometry has been optimised for the determination of haloanisoles in wines. This powerful analytical methodology is compared with several analytical approaches based on pervaporation, an innovative membrane-based technique similar to dynamic headspace. Analytical features of the methods assayed reveal their suitability for the appraisal of haloanisoles in this matrix in which threshold odor concentrations are in the range 4-40 ng l(-1). The analytical approaches have been applied to the analysis of haloanisoles in different Spanish white and red wines, in which spiking experiments showed good recoveries for the methodologies assayed.

Anisoles↗

PubMed2003

Identification of pheromones in mouse urine by head-space solid phase microextraction followed by gas chromatography-mass spectrometry.

Given the key role of pheromones in animal communication and behaviour, there is need to identify the different classes of these molecules under varying physiological conditions. However, the highly volatile nature of pheromones and the fact that they occur at very low concentrations in urine makes this task all the more difficult. Herein, we present a method of detecting and identifying the five main pheromones known: 2-sec-butyl-4,5-dihydrothiazole, geraniol, indole, trans-beta farnesene and trans-alpha farnesene in individual urine microsamples taken from male mice. Urine volumes as small as 20 microl were subjected to solid phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS). This selective analytical method permits the rapid detection of these pheromones free from cross-contaminants as a clearly distinguishable spectral signals. Highest recovery rates of natural pheromones were achieved by extraction on a carboxen/polydimethylsiloxane (CAR/PDMS) fibre of 85 microm film thickness. This selective, sensitive and accurate method will help address the question of possible links between certain pheromone classes, and social and reproductive behaviour in mice.

Animals↗

PubMed2001

Flavor threshold for acetaldehyde in milk, chocolate milk, and spring water using solid phase microextraction gas chromatography for quantification.

The detection threshold of acetaldehyde was determined on whole, lowfat, and nonfat milks, chocolate-flavored milk, and spring water. Knowledge of the acetaldehyde threshold is important because acetaldehyde forms in milk during storage as a result of light oxidation. It is also a degradation product of poly(ethylene terephthalate) during melt processing, a relatively new packaging choice for milk and water. There was no significant difference in the acetaldehyde threshold in milk of various fat contents, with thresholds ranging from 3939 to 4040 ppb. Chocolate-flavored milk and spring water showed thresholds of 10048 and 167 ppb, respectively, which compares favorably with previous studies. Solid phase microextraction (SPME) was verified as an effective method for the recovery of acetaldehyde in all media with detection levels as low as 200 and 20 ppb in milk and water, respectively, when using a polydimethyl siloxane/Carboxen SPME fiber in static headspace at 45 degrees C for 15 min.

Acetaldehyde↗