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PubMed2006

Determination of parathion in biological fluids by means of direct solid-phase microextraction.

A new and simple procedure for the determination of parathion in human whole blood and urine using direct immersion (DI) solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) is presented. This technique was developed using only 100 microL of sample, and ethion was used as internal standard (IS). A 65-microm Carbowax/divinylbenzene (CW/DVB) SPME fibre was selected for sampling, and the main parameters affecting the SPME process such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH effect were optimized to enhance the sensitivity of the method. This optimization was also performed to allow the qualitative determination of parathion's main metabolite, paraoxon, in blood. The limits of detection and quantitation for parathion were 3 and 10 ng/mL for urine and 25 and 50 ng/mL for blood, respectively. For paraoxon, the limit of detection was 50 ng/mL in blood. The method showed linearity between the LOQ and 50 microg/mL for both matrices, with correlation coefficients ranging from 0.9954 to 0.9999. Precision and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries were 35.1% for urine and 6.7% for blood. Other parameters such as dilution of sample and stability were also validated. Its simplicity and the fact that only 100 microL of sample is required to accomplish the analysis make this method useful in forensic toxicology laboratories to determine this compound in intoxications, and it can be considered an alternative to other methods normally used for the determination of this compound in biological media.

Humans↗

PubMed2006

Characterization and semiquantitative analysis of volatiles in seedless watermelon varieties using solid-phase microextraction.

Seedless triploid watermelons have increased in popularity since the early 1990s, and the demand for seedless fruit is on the rise. Sweetness and sugars are crucial breeding focuses for fruit quality. Volatiles also play an important role; yet, we found no literature for seedless varieties and no reports using solid-phase microextraction (SPME) in watermelon. The objective of this experiment was to identify volatile and semivolatile compounds in five seedless watermelon varieties using carboxen divinylbenzene polydimethylsiloxane solid-phase microextraction (SPME) with gas chromatography-mass spectrometry (GC-MS). Fully ripe watermelon was squeezed through miracloth to produce rapid juice extracts for immediate headspace SPME GC-MS. Aldehydes, alcohols, ketones, and one furan (2-pentyl furan, a lipid oxidation product) were recovered. On the basis of total ion count peak area, the most abundant compounds in five varieties were 3-nonen-1-ol/(E,Z)-2,6-nonadienal (16.5-28.2%), (E)-2-nonenal (10.6-22.5%), and (Z)-6-nonenal (2.0-11.3%). Hexanal was most abundant (37.7%) in one variety (Petite Perfection) [corrected] The most abundant ketone was 6-methyl-5-hepten-2-one (2.7-7.7%). Some sensory attributes reported for these compounds are melon, citrus, cucumber, orange, rose, floral, guava, violet, vegetable, green, grassy, herbaceous, pungent, fatty, sweet, and waxy. Identifying and relating these compounds to sensory attributes will allow for future monitoring of the critical flavor compounds in seedless watermelon after processing and throughout fresh-cut storage.

Alcohols↗

PubMed2001

Application of on-site solid-phase microextraction in aquatic dissipation studies of profoxydim in rice.

The application of a manual operated solid-phase microextraction (SPME)-HPLC interface is discussed for the analysis of thermally labile analytes in aqueous matrices. The technique has been applied on-site at a flooded rice field to demonstrate its potential for real time extraction of the herbicide profoxydim. Thus, compounds which would otherwise easily degrade in the aqueous matrices within hours or days could be determined more accurately. The fibers were shipped back to the laboratory with express delivery where the target analyte was desorbed from the fiber and determined by HPLC-UV analysis. The SPME method was characterized by significant ruggedness where conventional techniques such as liquid-liquid extraction and solid-phase extraction require additional shipping and handling costs and time-consuming multiple sample preparation steps. In general, any delay in shipping the aqueous samples to the laboratory has the potential for sample degradation and a loss in accuracy when using non on-site extraction techniques. Fifty microm Carbowax-templated resin coatings were most suitable for coupling SPME to HPLC in order to achieve a high sensitivity for polar analytes. The SPME technique was characterized by a good sensitivity and a precision less than 10% RSD. The SPME-LC-UV method was linear over at least three orders of magnitude while achieving a limit of detection in the lower microg/l range. The on-site SPME method has shown significantly increased accuracy. Profoxydim was determined at concentrations of ca. 180 microg/l 3 h after an application on a flooded bare soil field.

Benzene Derivatives↗

PubMed2004

An evaluation of solid phase microextraction for analysis of odorant emissions from stored biosolids cake.

Odors are a common occurrence at wastewater treatment plants, biosolids processing facilities and biosolids recycling locations. Accurate, objective measurement techniques are needed to monitor emissions, to develop new waste handling procedures and to reduce the production of the volatile gases. The objective of this study was to evaluate the use of solid phase microextraction for measuring common odorants that are found in biosolids facilities. The odorants were collected and concentrated by solid phase microextraction (SPME) and then quantified by gas chromatography with detection by mass spectrometry. A 75-microm Carboxen-Polydimethylsiloxane coating was used for the analysis of trimethylamine, dimethyl sulfide, dimethyl disulfide and methyl mercaptan. Gaseous standards were generated for individual compounds and for dry and wet mixture from permeation apparatus. The differences in sensitivity between fibers, the competition between analytes and water vapor for the active sites on the fiber and the lack of production of artifacts make SPME suited for qualitative analysis and enables quick screening for the identification of compounds with adverse organoleptic characteristics.

Adsorption↗

PubMed2006

Suitability of solid-phase microextraction for the determination of organophosphate flame retardants and plasticizers in water samples.

The feasibility of solid-phase microextraction (SPME) for the determination of several organophosphorus flame retardants and plastizicers in water samples by gas chromatography-nitrogen phosphorous detection (GC-NPD) is evaluated. These compounds have a wide range of polarities and volatilities and require a thorough optimisation of the different SPME parameters. Considering also possible contamination and carryover sources, the best compromise microextraction conditions were found to be direct extraction of 22 ml samples, containing 300 mg/ml of NaCl, with a PDMS-DVB coated fibre at room temperature. Although equilibrium was not achieved, an extraction time of 40 min allowed obtaining a good sensitivity (quantification limits between 0.010 and 0.025 ng/ml), comparable to that achieved by solid-phase extraction (SPE) of 1l samples, producing both similar values of precision and accuracy. Furthermore, the SPME method has shown to be free of matrix effects, avoiding the need of employing the standard addition procedure for quantification, and was suitable for the determination of eight of the nine considered compounds. Only tris-(2-ethylhexyl)-phosphate was neither determinable by SPME nor by SPE. Finally, the application of the developed methodology to the analysis of wastewater samples, showed that important concentrations of these compounds (up to 10 ng/ml) have been detected in treated sewage water, being discharged into the aquatic environment.

Chromatography, Gas↗

PubMed2004

Applicability of headspace solid-phase microextraction to the determination of multi-class pesticides in waters.

The applicability of headspace solid-phase microextraction (HS-SPME) to pesticide determination in water samples was demonstrated by evaluating the effects of temperature on the extraction of the pesticides. The evaluations were performed using an automated system with a heating module. The 174 pesticides that are detectable with gas chromatograph were selected objectively and impartially based on their physical properties: vapor pressure and partition coefficient between octanol and water. Of the 174 pesticides, 158 (90% of tested) were extracted with a polyacrylate-coated fiber between 30 and 100 degrees C and were determined with gas chromatograph-mass spectrometry. The extraction-temperature profiles of the 158 extracted pesticides were obtained to evaluate the effects of temperature on the extraction of pesticides. The pesticides were classified into four groups according to the shape of their extraction-temperature profiles. The line of demarcation between extractable pesticides and non-extractable pesticides could be drawn in the physical property diagram (a double logarithmic plot of their vapor pressure and partition coefficient between octanol and water). The plot also revealed relationships between classified extraction features and their physical properties. The new method for multi residue screening in which the analytes were categorized into sub-groups based on extraction temperature was developed. In order to evaluate the quantitivity of the developed method, the 45 pesticides were chosen among the pesticides that are typically monitored in waters. Linear response data for 40 of the 45 was obtained in the concentration range below 5 microg/l with correlation coefficients ranging between 0.979 and 0.999. The other five pesticides had poor responses. Relative standard deviations at the concentration of the lowest standard solution for each calibration curve of the pesticides ranged from 3.6 to 18%. The value of 0.01 microg/l in the limits of detection for 17 pesticides was achieved only under the approximate conditions for screening, not under the individually optimized conditions for each pesticide. Recoveries of tested pesticides in actual matrices were essentially in agreement with those obtained by solid-phase extraction.

Chromatography, Gas↗

PubMed2000

Application of solid-phase microextraction for determination of organic vapours in gaseous matrices.

This paper reviews the practical applications of solid-phase microextraction (SPME) in the analysis of organic vapours which are pollutants of atmospheric air, indoor air and workplace air. Applications to headspace of solids and liquids such as different waters, soils, food, etc., are also included. Problems related to calibration in SPME analysis of gaseous matrices are also dealt with. Calibration procedures and apparatus for generation of standard gaseous mixtures are described. Advantages and limitations of SPME based gas chromatographic methods of air organic pollutants are discussed.

Calibration↗

PubMed1999

Solid-phase microextraction gas chromatography/mass spectrometric analysis of volatile organic compounds in water

In this work, a solid-phase microextraction (SPME) method for the extraction of volatile organic compounds (VOCs) from water samples has been developed. Fifty-five volatile compounds (from the sixty listed in EPA method no. 524.2) were extracted from aqueous solutions using an SPME fiber coated with Carboxen-polydimethylsiloxane (Carboxen-PDMS), 75 &mgr;m film thickness. Time of sampling and chromatographic separation conditions were optimised. Standard solutions of VOC mixtures with concentrations as low as 0.05 ppb were analysed and their signal/noise ratios measured. Linearity of response for each component of the mixture was tested and mass spectral quality evaluated. A comparison with purge and trap analysis of VOCs was made. The method was applied to real-world samples of drinking, surface and leaching waters. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMed2003

Application of solid-phase microextraction for the determination of pyrethroid residues in vegetable samples by GC-MS.

A solid-phase microextraction (SPME) method has been developed for the determination of 7 pyrethroid insecticides (bifenthrin, lambda-cyhalothrin, permethrin, cyfluthrin, cypermethrin, fenvalerate, and tau-fluvalinate) in water, vegetable (tomato), and fruit (strawberry) samples, based on direct immersion mode and subsequent desorption into the injection port of a GC/MS. The SPME procedure showed linear behavior in the range tested (0.5-50 microg L(-1) in water and 0.01-0.1 mg kg(-1) in tomato) with r(2) values ranging between 0.97 and 0.99. For water samples limits of detection ranged between 0.1 and 2 microg L(-1 )with relative standard deviations lower than 20%. Detection limits for tomato samples were between 0.003 and 0.025 mg kg(-1) with relative standard deviations around 25%. Finally, the SPME procedure has been applied to vegetable (tomato) and fruit (strawberry) samples obtained from an experimental plot treated with lambda-cyhalothrin, and in both cases the analyte was detected and quantified using a calibration curve prepared using blank matrix. SPME has been shown to be a simple extraction technique which has a number of advantages such as solvent-free extraction, simplicity, and compatibility with chromatographic analytical systems. Difficulties with the correct quantification in a complex matrix are also discussed.

Food Analysis↗

PubMed1996

Head-space solid phase microextraction for the GC-MS analysis of terpenoids in herb based formulations.

Head-Space Solid Phase Microextraction (HS-SPME) has been employed for sampling of volatile components and their volatile decomposition products occurring in herbal medicines and herb extracts with subsequent injection into a gas chromatographic column. The identification and quantification was performed by coupled gas chromatography - mass spectrometry (GC-MS) with classical splitless injection, electron impact ionization and a quadrupole mass analyzer. As fast and inexpensive technique for the isolation of organic analytes HS-SPME with GC-MS can be successfully employed for the quality control of herbal medicines and other formulations containing herb extracts. Analytical results with satisfying accuracy and precision are given.

Journal Article↗

PubMed2004

Solid-phase microextraction coupled with high-performance liquid chromatography for the analysis of heterocyclic aromatic amines.

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) with UV diode array detection (DAD) for the analysis of heterocyclic aromatic amines (HAs) is described. Four kinds of fiber coatings: Carbowax-templated resin (CW-TPR), Carbowax-divinylbenzene (CW-DVB), poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) and polyacrylate (PA) were evaluated for extraction of nine most biologically active heterocyclic aromatic amines. Different parameters affecting to the microextraction and determination of HAs were studied, such as absorption and desorption time, desorption mode, composition of the solvent for desorption, pH, ionic strength, and percentage of methanol in the sample. To determine these amines in food samples a new simplified procedure is proposed, consisting of treatment of the sample with methanolic NaOH prior microextraction by CW-TPR fiber coating and HPLC-DAD determination. The advantages of this new method are the reduced amounts of time and organic solvents required.

Amines↗

PubMed2005

Optimization of solid-phase microextraction conditions for the determination of triclosan and possible related compounds in water samples.

A solid-phase microextraction (SPME) method for the determination of triclosan, methyl triclosan, 2,4-dichlorophenol and 2,3,4-trichlorophenol (considered as possible triclosan metabolites) in water samples was optimised. Analytes were first concentrated on a SPME fibre, directly exposed to the sample, and then triclosan and the two chlorinated phenols on-fibre silylated using N-methyl-N-(tert.-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA). Methyl triclosan remained unaffected during the derivatization step. Compounds were determined using gas chromatography in combination with mass spectrometry (GC-MS). Influence of different factors on the efficiency of extraction and derivatization steps was systematically investigated. Using a polyacrylate (PA) fibre quantification limits below 10 ng/l, and acceptable relative standard deviations, were obtained for all compounds after an extraction time of 30 min. On-fibre silylation was carried out in only 10 min. Moreover, the efficiency of the procedure was scarcely affected by the type of water sample. The method was applied to several samples of treated and raw wastewater, triclosan was found in all samples, at concentrations from 120 to 14,000 ng/l, and 2,4-dichlorophenol in most of them, at levels up to 2222 ng/l.

Acetamides↗

PubMed2005

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.

Chromatography, Gas↗

PubMed2005

Identification of impurities and the statistical classification of methamphetamine using headspace solid phase microextraction and gas chromatography-mass spectrometry.

The profiling of impurities in methamphetamine (MA) using headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) is described. The extraction of the impurities with an SPME fiber was examined under varying conditions. Optimal chromatograms were obtained when a 50 mg MA sample at 85 degrees C for 30 min was extracted using a fiber coated with divinylbenzene/carboxen/polydimethylsiloxane. MA samples from nine different origins were analyzed under optimized extraction conditions. Compounds related to MA such as benzaldehyde, benzyl alcohol, amphetamine, benzyl methyl ketone, cis- and trans-1,2-dimethyl-3-phenylaziridine, dimethylamphetamine, N-acetylamphetamine, N-acetylmethamphetamine and N-formylmethamphetamine were detected in the chromatograms. Trace amounts of ethanol, diethyl ether and acetic acid were also detected in some of the chromatograms. The numbers and intensities of the peaks detected were different, depending on the sample. After the areas of the eight principal peaks were converted to their square root and logarithm, similarities among the samples were evaluated by Euclidian distance, cosine distance and correlation coefficient. The results showed that a combination of logarithmic conversion and cosine distance was the most suitable for discriminating and classifying the samples. HS-SPME/GC-MS is a simple and effective method for the extraction and identification of impurities. The present method, in combination with an appropriate statistical analysis, would be useful for developing a profile of impurities in MA.

Journal Article↗

PubMed2005

Application of solid-phase microextraction to in vitro skin permeation experiments: example using diethyl phthalate.

The application of automated solid-phase microextraction (SPME) as a sample preparation technique for in vitro studies of skin permeation is described, using diethyl phthalate (DEP) as an example. In vitro diffusion cell experiments and skin-vehicle partition coefficient determinations require quantitative analysis of low-level analytes in aqueous samples. SPME is an ideal candidate for sample preparation for subsequent gas chromatographic analysis, offering numerous advantages over other methods. SPME conditions were optimized and the automated method was found to exhibit adequate sensitivity and good precision (relative standard deviation=3%). Abdominal skin (dermatomed at 350 microm) from male hairless guinea pigs (n=6) was used to measure DEP skin permeation parameters. In vitro methods were employed to determine permeability coefficient (k(p)), time lag (tau) and skin-buffer partition coefficient (K(SB)) for 2 mM DEP in HEPES buffered Hanks Balanced Salt Solution. Measurements (mean+/-standard deviations) are: k(p), 0.021+/-0.012 cm/h; tau, 0.67+/-0.18 h; K(SB), 4.74+/-0.68. The skin may be a significant route for the uptake of DEP.

Animals↗

PubMed2001

Preparation and applications of polypyrrole films in solid-phase microextraction.

Polypyrrole (PPY) and poly-N-phenylpyrrole (PPPY) films were prepared and applied for solid-phase microextraction (SPME). The extraction properties of the new films to volatile organic compounds were examined using an SPME device coupled with GC-flame ionization detection. A PPY-coated capillary was applied for in-tube SPME to evaluate its extraction efficiency towards less volatile compounds and ionic species. The porous surface structures of the films, revealed by scanning electron microscopy, provided high surface areas and allowed for high extraction efficiency. Compared with commercial SPME stationary phases, the new phases showed better selectivity and sensitivity toward polar, aromatic, basic and anionic compounds, due to their inherent multifunctional properties. In addition, PPY and PPPY films showed different selectivity to various groups of compounds studied, indicating that the selectivity of the films could be modified by introducing a new functional group (phenyl in PPPY) into the polymer. For in-tube SPME, the PPY-coated capillary showed superior extraction efficiency to commercial capillaries for a variety of compounds, demonstrating its potential applications for a wide range of analytes when coupled with HPLC. The sensitivity and selectivity of the films for SPME could be tuned by changing the film thickness. These results are in line with both the theoretical expectations and the results obtained by other methods, which indicate not only that PPY films can be used as new stationary phases for SPME. but also that SPME method may provide an alternative tool for studying materials like polypyrrole.

Capillary Action↗

PubMed2002

Solid-phase microextraction coupled to high-performance liquid chromatography to determine phenolic compounds in water samples.

Solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with ultraviolet (UV) and electrochemical detection (ED) has been applied to determine 11 phenolic compounds considered priority pollutants by the US Environmental Protection Agency. 85 microm polyacrylate fibers were used to extract the analytes from the aqueous samples. Two different designs of the liquid chromatograph were compared in combination with SPME. Dynamic and static modes of desorption in both HPLC designs were compared and the variables affecting both absorption and desorption processes in SPME-HPLC were optimized. Static desorption in both HPLC systems showed better recoveries for the phenolic compounds. The performance of the SPME-HPLC-UV-ED method was evaluated with river water and wastewater samples. The method enabled the determination of phenolic compounds at low levels in these water samples.

Chromatography, High Pressure Liquid↗

PubMed2003

Detection of VX contamination in soil through solid-phase microextraction sampling and gas chromatography/mass spectrometry of the VX degradation product bis(diisopropylaminoethyl)disulfide.

A solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) sampling and analysis method was developed for bis(diisopropylaminoethyl)disulfide (a degradation product of the nerve agent VX) in soil. A 30-min sampling time with a polydimethylsiloxane-coated fiber and high temperature alkaline hydrolysis allowed detection with 1.0 microg of VX spiked per g of agricultural soil. The method was successfully used in the field with portable GC-MS instrumentation. This method is relatively rapid (less than 1 h), avoids the use of complex preparation steps, and enhances analyst safety through limited use of solvents and decontamination of the soil before sampling.

Chemical Warfare Agents↗