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Results for “Solid Phase Microextraction”

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PubMed2004

Analysis of sulfur and nitrogen odorants using solid-phase microextraction and GC-MS.

An analytical method involving solid-phase micro-extraction (SPME) and gas chromatography-mass spectrometry (GC-MS) was applied to analyze biosolids odors. A selective ion monitoring (SIM)-based MS method was developed, using SPME injections of odorant standards under the full-scan mode to select the quantification and confirmation ions for each odorant. The odorants analyzed in this study include: dimethylsulfide, dimethyldisulfide, methyl mercaptan, hydrogen sulfide, carbon disulfide, trimethylamine and dimethylamine. We have used this method to quantify parts-per-billion levels of odorant vapors produced during anaerobic incubation of digested wastewater sludge. Important considerations for expedient and accurate calibration under static and dynamic flow conditions are discussed. The SPME-GC-MS method may give a positive intercept in the calibration curve, especially under static sampling conditions, which sets a practical detection limit for odor analysis.

Chemistry Techniques, Analytical↗

PubMed2004

Fast speciation analysis of iodophenol compounds in river waters by capillary electrophoresis-inductively coupled plasma-mass spectrometry with off-line solid-phase microextraction.

An analytical methodology for the fast separation and determination of iodophenol species in natural water samples was developed using capillary electrophoresis (CE) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Based on the element-specific and highly sensitive detection provided by ICP-MS, the methodology has been applied to the analysis of 2-iodophenol, 4-iodophenol, and 2,4,6-triiodophenol. The use of solid-phase microextraction (SPME), after proper optimization, improved the signal by a factor of 100 leading to detection limits in the sub microg.L(-1). Different desorption conditions of iodophenol compounds from the SPME microfiber were studied to achieve the optimum preconcentration factor and best analytical performance. Different CE conditions were studied to achieve complete baseline separation of iodophenols in short migration times. Three different CE buffer systems were evaluated using ICP-MS detection. A buffer solution containing 20 mmol.L(-1) 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and an applied potential of +22 kV were finally selected leading to a maximum separation time of 6.6 min. A relative standard deviation (%RSD) of about 5.0% for ten consecutive determinations was obtained. Finally, the speciation methodology developed was utilized for the determination of iodophenol compounds in natural water samples.

Buffers↗

PubMed2005

Behaviour of carbamate pesticides in gas chromatography and their determination with solid-phase extraction and solid-phase microextraction as preconcentration steps.

This work reports a study of the chromatographic behaviour of seven carbamate pesticides (aldicarb, carbetamide, propoxur, carbofuran, carbaryl, methiocarb, and pirimicarb) by gas chromatography-mass spectrometry (GC-MS). Variables such as injector temperature, solvent, injection mode, and the degree of ageing of the chromatographic column were studied. One of the aims of this work was to achieve a controlled decomposition of carbamates by a solid-phase microextraction (SPME) preconcentration step with a polyacrylate fibre in order to obtain reproducible chromatographic signals of the degradation products. Optimisation of the SPME process was accomplished by means of experimental design. Several methods using ultrapure water were developed with different preconcentration configurations: SPME-GC-MS, SPE followed by SPME-GC-MS, and SPE plus GC-MS. For all the pesticides studied, method detection limit (MDL) values below 0.1 microg L-1 were reached in at least one of the proposed configurations.

Carbamates↗

PubMed2006

Establishment of long-term preservation for dimethyl sulfide by the solid-phase microextraction method.

Dimethyl sulfide (DMS) derived from marine biological activity affects radiative forcing of the climate. The general analytical technique for DMS in seawater (purge and trap analytical method, P&T) is complex onboard ship. Thus it is difficult to obtain sufficient data for a comprehensive understanding of the spatiotemporal variability of DMS in the sea surface layer. On the other hand, a new analytical method for DMS using SPME (solid-phase microextraction) has recently been developed as an alternative method to P&T. This method is simpler than P&T because no special or complex apparatus is needed. If it is possible to preserve DMS for an extended period in excess of the duration of the cruise, the SPME method is a promising method for measuring DMS in seawater. We assessed an analytical method which can allow us to preserve DMS on the long-term scale using SPME. In liquid nitrogen (-196 degrees C), as preserved environment, for a period of 20 days after sampling, we found the preservation rate of DMS to be 94.7 +/- 4.4% (n = 6) in this study. Furthermore, estimating the distribution coefficient with respect to the effect of salinity on SPME, we found that DMS changed by 0.1 nM/% sal, suggesting that salinity has only a minor influence on oceanic DMS measurements in the open ocean because the minimal change of the open ocean salinity is within 2 %. Applying the SPME method to open ocean samples, we found that there were no significant differences in DMS between the unpreserved and preserved samples (r = 0.99, n = 26, SE = 0.01, p < 0.0001), showing the SPME method has potential for use for open ocean surveys.

Chromatography, Liquid↗

PubMed2002

Application of solid-phase microextraction combined with gas chromatography-mass spectrometry to the determination of butylated hydroxytoluene in bottled drinking water.

Butylated hydroxytoluene (BHT) is an antioxidant utilized as additive in foods and packaging plastic. Its presence in drinking water is possible if it is used as an antioxidant in the packaging plastic because it may migrate into the package's contents. A method for the determination of BHT in water by means of solid-phase microextraction and gas chromatography-mass spectrometry has been developed and evaluated with respect to the time of fiber exposure, limits of detection and quantitation, linearity and precision. Finally, the method was applied to evaluate the presence of this substance in samples of mineral and mineralized bottled drinking water, and it appeared to be present in seven out of a total of fifteen commercial brands.

Butylated Hydroxytoluene↗

PubMed2000

Identification and characterization of fenton oxidation products of surfactants by electrospray mass spectrometry and by solid phase microextraction gas chromatography mass spectrometry. 2. Fatty alcohol polyethoxy sulphates

The Fenton reaction for the degradation of surfactants has been investigated and partial degradation products have been identified and characterized by mass spectrometry for the case of fatty alcohol polyethoxy sulphates. The polar water-soluble products were investigated by liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization (ESI), and the volatile products leaving the mixture during the reaction were trapped by means of solid phase microextraction (SPME) and investigated by gas chromatography/mass spectrometry (GC/MS) with electron and chemical ionization. The oxidation leads to the formation of products with hydroxyl and epoxide groups due to insertion of oxygen atoms or with terminal ethoxylic moieties deriving from the loss of the hydrophilic sulphate group. The formation of volatile aldehydes is also observed, corresponding to the fragmentation between hydrocarbon and ethoxylic chains. The extent of mineralization is dependent on peroxide and iron(II) concentrations. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗

PubMed2006

Influence of the soil matrices on the analytical performance of headspace solid-phase microextraction for organotin analysis by gas chromatography-pulsed flame photometric detection.

Organotin compounds (OTCs) have been identified in a variety of environmental media (air, surface water, groundwater, soil and sediments). In the past, much attention was assigned to the study of the OTCs content in biological samples, water and sediments. Little information about OTCs in soil is available. In this work, a procedure for butyl and phenyltin determination in soils by headspace-solid-phase microextraction (HS-SPME) gas chromatography-pulsed flame photometric detection (GC-PFPD) was investigated. For SPME analysis, a polydimethylsiloxane (PDMS) coating was applied. Peat soil rich in organic matter and with a high cation-exchange capacity (CEC), and clay soil low in organic matter and with a low CEC were analysed. The influence of these different soil matrices on HS-SPME analysis was evaluated by spiking of samples. In general, the recoveries for the two spiked soils exceeded 80%. The repeatability of the method was better than 10%. The limits of detection (LODs) and limits of quantification (LOQs) were in the ng S ng(-1) range. The technique may be reliably applied for the determination of butyltins and monophenyltin in soils, while it shows some limitations for the analysis of di- and triphenyltin (TPhT).

Chromatography, Gas↗

PubMed1999

Development of a solid phase microextraction method for detection of the use of banned azo dyes in coloured textiles and leather

A new method to detect the use of banned azo dyes in the manufacture and treatment of coloured textiles and leather is described. The determination of the azo dyes was made by quantification of aromatic amines generated by reductive cleavage in a citrate buffer medium. The aromatic amines were then extracted from 1 mL of the reaction solution by means of solid phase microextraction (SPME) and determined by gas chromatography/mass spectrometry (GC/MS). We also evaluate accuracy, precision, range of linearity and limit of detection for the eighteen aromatic amines investigated, and show that the method is comparable with current established methods. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMed2002

Optimization of solid-phase extraction and solid-phase microextraction for the determination of alpha- and beta-endosulfan in water by gas chromatography-electron-capture detection.

Water contamination due to the wide variety of pesticides used in agriculture practices is a global environmental pollution problem. The 98/83/European Directive requires to measure residues of pesticides at a target concentration of 1.0 microg/l in surface water and 0.1 microg/l in drinking water. In order to reach the level of detection required, efficient extraction techniques are required. Although solid-phase extraction (SPE) is the most common technique for isolation and concentration of pesticides from water, solid-phase microextraction (SPME) is being increasingly applied for this purpose. In this study, a direct-SPME procedure has been developed for the determination of alpha-endosulfan and beta-endosulfan in waters; experimental parameters such as selection of SPME coating, effect of temperature, effect of salt addition, optimization of the sample volume, adsorption and desorption profiles and desorption temperature were studied and optimized. Analytical parameters such as linearity, precision, detection and quantitation limits, and matrix effects for SPE and SPME methods were evaluated for comparison purposes with the aim of selecting the most appropriate for a certain application. Both extraction techniques, SPE and SPME, were followed by gas chromatography with electron-capture detector.

Chromatography, Gas↗

PubMed2004

Detection of cocaine and cocaethylene in sweat by solid-phase microextraction and gas chromatography/mass spectrometry.

In the present work, a semi-quantitative method was developed to detect simultaneously cocaine (COC) and cocaethylene (CE) (transesterification product of the coingestion of COC with ethanol) in sweat. Sweat samples were collected by means of a non-occlusive sweat patch device supplied by PharmChek. The method was based on the dissolution of COC and CE incorporated into the patch, with 0.2 M sodium acetate buffer (pH 5.0) and the extraction of the analytes by solid-phase microextraction (SPME). Gas chromatography/mass spectrometry (GC-MS) was used to detect the analytes in selected ion monitoring mode (SIM). The method showed to be very simple, rapid and sensitive. The limits of detection were 5 ng/ml for COC and CE (12.5 ng/patch). Good inter and intra-assay precision was also observed (coefficient of variation <8%) with the use of deuterated internal standards.

Cocaine↗

PubMed2003

"Cold" solid-phase microextraction method for the determination of volatile halocarbons present in the atmosphere at ultra-trace levels.

Anthropogenic volatile halocarbons are compounds of great enviromnental concern because of their involvement in global change phenomena. They are present in the atmosphere at concentration levels in the order of parts per trillion by volume. The chosen analytical method for their determination is capillary gas chromatography coupled to mass spectrometry, preceded by an enrichment step on suitable adsorbent resins. The method here presented makes use of the solid-phase microextraction as a pre-analytical technique, using sub-ambient temperature in order to enhance the retention capability of the fiber coating. The proposed method was evaluated in terms of extraction efficiency, linearity, reproducibility, andlimits of detection. Results obtained showed that trace atmospheric halocarbons are detectable even when enriching very small air sample volumes. A good chromatographic resolution is obtained as a consequence of the extremely low injection volume. Finally a standard GC-MS instrumentation equipped with a simple split-splitless injector was employed, thus avoiding the use of expensive dedicated apparatus. The method was also applied to the analysis of actual samples collected both in remote, and in semi-remote sites.

Air Pollutants↗

PubMed2002

Gas chromatographic-mass spectrometric analysis of residual solvent trapped into illicit cocaine exhibits using head-space solid-phase microextraction.

The analysis of solvent residues trapped into crystals of illicit drugs provides useful evidence for monitoring current use trend in the chemical underground, and is also a suitable tool to achieve the complete chemical characterisation of street drugs for comparative examination of separate specimens. This paper describes a method developed in order to perform simultaneous qualitative and quantitative analysis of solvent residues in cocaine samples. The method is based on GC-MS analysis of solvents after their extraction/concentration from drug matrices accomplished by solid-phase microextraction (SPME) in static head space. The proposed method has been used to detect residues of solvents in 47 illicit street cocaine samples. Quantitative analyses were carried out only for the solvents identified at concentration values higher than 1 ppm. Statistical evaluation of our results allowed us to group the illicit samples into various classes according to different kinds of residual solvent, in connection with different clandestine manufacturing processes used to prepare illicit cocaine.

Cocaine↗

PubMed2002

Determination of nicotine and other minor alkaloids in international cigarettes by solid-phase microextraction and gas chromatography/mass spectrometry.

Nicotine, nornicotine, anabasine, and anatabine are the most abundant alkaloids in tobacco. Along with the addictiveness of nicotine, other properties, including their occurrence in tobacco at relatively high concentrations, and as the primary precursors for the highly carcinogenic tobacco-specific nitrosoamines, make these chemicals important from a public health standpoint Therefore, developing a fast and accurate quantitative method to screen large numbers of cigarette samples for these alkaloids was important. This report describes the first use of headspace analysis using solid-phase microextraction combined with gas chromatography/mass spectrometry for the unambiguous detection of tobacco alkaloids. Detection and confirmation of each analyte isestablished by both chromatographic retention times and the ratio of reconstructed ion chromatogram peak areas from characteristic quantitation ion and confirmation ion. Twenty-eight cigarette brands from 14 countries were analyzed. Surprisingly, the minor alkaloids' response factors varied considerably among different styles of cigarettes. Accurate quantification was achieved using a three-point standard addition protocol. The standard addition approach was essential to obtain accurate measurements by minimizing matrix effects that would otherwise have contributed to quantitation bias. Significant differences in the alkaloid profiles were measured in the different cigarette brands. These results strongly suggest that such differences reflect variations associated with blend compositions, tobacco quality, and manufacturing practices.

Alkaloids↗

PubMed2002

Optimization of solid-phase microextraction conditions for gas chromatographic determination of ethanol and other volatile compounds in blood.

A procedure for the determination of acetaldehyde, acetone, methanol, ethanol, 1-propanol and 2-propanol in blood was developed. Separation of analytes was carried out on DB-wax capillary column (l = 30 m, I.D. = 0.32 mm, dF = 0.5 microm) at 40 degrees C, hydrogen was used as a carrier gas (at 30 kPa) and FID as a detector. Quantification was performed with the use of 2-butanol as an internal standard. Headspace solid-phase microextraction was applied as the sample preparation technique. The usefulness of most commercially available fiber coatings was checked and 65 microm Carbowax/DVB proved most effective. Microextraction was carried out from the headspace at 60 degrees C for 10 min. The sample was stirred at 750 rpm. In order to improve the extraction efficiency of analytes, salting-out agents were also applied. Potassium carbonate turned out to be the most efficient. A 1.0-g amount of this salt and 0.1 ml of I.S. were added to 0.5 ml of sample. Validation of the worked-out method was performed. For each analyte, the limits of detection and quantification, linearity, working range, accuracy and precision were determined or tested.

Acetaldehyde↗

PubMed2005

Thermal desorption solid-phase microextraction inlet for differential mobility spectrometry.

A splitless thermal desorber unit that interfaces a differential mobility spectrometry (DMS) sensor has been devised. This device was characterized by the detection of benzene, toluene, and xylene (BTX) in water. The detection of BTX in water is important for environmental monitoring, and ion mobility measurements are traditionally difficult for hydrocarbons in water because water competes for charge and quenches the hydrocarbon signals. This paper reports the use of a DMS with a photoionization source that is directly coupled to a solid-phase microextraction (SPME) desorber. The separation and detection capabilities of the DMS were demonstrated using BTX components. Detection limits for benzene, toluene, and m-xylene were 75, 50, and 5 microg mL(-1), respectively.

Adsorption↗

PubMed2003

Inactivation of acrolein by sodium 2-mercaptoethanesulfonate using headspace-solid-phase microextraction gas chromatography and mass spectrometry.

Acrolein, the metabolite of cyclophosphamide and ifosphamide, is an irritant of mucous membranes and seems to play an important role in hemorrhagic cystitis. Several methods are available to reduce the risk of hemorrhagic cystitis. Mesna is a regional detoxificant which inactivates acrolein. However, the interaction of mesna and acrolein has never been reported because no available method can detect acrolein. In this study, we measured acrolein to evaluate the effect of mesna in urine or phosphate-buffered saline using a headspace-solid-phase microextraction gas chromatography and mass spectrometry method which we had previously established. We also investigated the effect of mesna at different conditions of pH. Mesna was effective in a dose-dependent (10 microM to 20 mM) fashion in both urine and phosphate-buffered saline and completely inactivated acrolein at concentrations over 10 mM. Furthermore, mesna was more effective in alkaline conditions than in acid.

Acrolein↗

PubMed2004

Development of solid-phase extraction and solid-phase microextraction methods for the determination of chlorophenols in cork macerate and wine samples.

Tri-, tetra- and pentachlorophenol (TCP, TeCP and PCP) can be considered the precursors in the formation of corresponding chloroanisoles, known to be powerful odorants in corks and wine. Determining the presence of these chlorophenolic compounds in cork soaking solutions (ethanol/water mixtures, 12% (v/v) ethanol used for cork quality control testing), or in wine can be achieved by acetylation/gas chromatography electron-capture detection. In order to reach the required sensitivity, a previous preconcentration step is necessary. Solid-phase extraction (SPE) and headspace solid-phase microextraction (HS-SPME) have given good results for the preconcentration of TCP, TeCP and PCP in such matrices. The use of Oasis HLB cartridges gives acceptable recoveries for the three compounds when different volumes (50-250 mL) of cork macerate with concentrations ranging from 20 to 150 ng/L are processed. Preconcentration based on HS-SPME has also been optimised with a 100 microm polydimethylsiloxane fibre and in situ derivatization. The HS-SPME method allows chlorophenols in a cork soaking solution and in wine to be determined with a limit of detection of 1 ng/L for each compound (in cork macerate) and a repeatability of around 0.5%-5% (n=8) for a concentration level of 30 ng/L.

Chlorophenols↗

PubMed2002

Determination of 2,4,6-trichloroanisole in wines by headspace solid-phase microextraction and gas chromatography-electron-capture detection.

One of the most important problems in the wine world, today, is cork taint, which often has been chemically identified as 2,4,6-trichloroanisole (TCA). The perception limit of this compound is very low (close to 10 and 40 ng/l for white and red wines, respectively), so, even at such low concentrations, its presence becomes a problem in wine quality. A method for the analysis of TCA in white and red wines has been developed in our laboratory, using headspace solid-phase microextraction and gas chromatography with electron-capture detection. The method, which has been optimized using an experimental design, involves the use of fibres coated with polydimethylsiloxane (PDMS) and allows the analysis of TCA at very low concentrations (under 500 ng/l) with good accuracy (RSD < or = 10%). The limits of quantification of the method are 5 and 8 ng/l for white and red wines, respectively, while the limit of detection is 1 ng/l for both types of wine.

Anisoles↗