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PubMed2005

Extraction and analysis of different Cannabis samples by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry.

A headspace solid-phase microextraction combined with GC-MS method was developed for the extraction and analysis of cannabinoids from Cannabis samples. Different commercially available fibres were evaluated; polydimethylsiloxane 100 microm was selected as the most efficient one. In order to enhance sensitivity and reduce analysis time, the sampling temperature was studied and it showed that extraction should be performed at a high temperature (150 degrees C). In relation with the high lipophilicity of cannabinoids, a relatively long desorption time (3 min) was necessary to ensure a total transfer from the fibre into the injection port of the gas chromatograph. The method was finally applied to the extraction of Swiss marijuana samples from different regions. Data treatment by principal component analysis and hierarchical cluster analysis allowed a discrimination of the different batches.

Cannabidiol↗

PubMed2006

Determination of butyltin and octyltin stabilizers in poly(vinyl chloride) products by headspace solid-phase microextraction and gas chromatography with flame-photometric detection.

Headspace solid-phase microextraction (HS-SPME) and gas chromatography with flame photometric detection (GC-FPD) have been investigated for determination of butyltin and octyltin stabilizers in poly(vinyl chloride) (PVC) products. The organotin stabilizers were first released from the plastic matrix by dissolving the PVC sample in tetrahydrofuran (THF). The stabilizers were then hydrolyzed to the chloride forms, by treatment with 6 mol L(-1) HCl, then derivatized with sodium tetraethylborate (NaBEt4) in 0.2 mol L(-1) sodium acetate buffer (pH 4.5) at 50 degrees C. HS-SPME was performed with a fused-silica fiber coated with a 100-microm film of polydimethylsiloxane (PDMS). The collected organotin compounds were then desorbed in the GC injector at 280 degrees C and analyzed by GC-FPD. Linearity (r > or =0.994) over a concentration of approximately two orders of magnitude was usually obtained. Limits of quantitation (LOQ) of the four organotin compounds studied, viz., monobutyltin (MBT), dibutyltin (DBT), monooctyltin (MOT), and dioctyltin (DOT), were in the range 0.3-1.0 ng Sn mL(-1). Recovery was >90% for butyltins and >80% for octyltins. The method was validated by analyzing two reference standard PVC sheets with known organotin content. The applicability of the method to analysis of organotin stabilizers in commercial PVC products was also demonstrated.

Chromatography, Gas↗

PubMed2004

Monitoring of drugs and metabolites in whole blood by restricted-access solid-phase microextraction coupled to liquid chromatography-mass spectrometry.

Robust biocompatible solid-phase microextraction (SPME) devices were prepared using various alkyldiol-silica (ADS) restricted-access materials (RAM) as the SPME coating. The ADS-SPME approach was able to simultaneously fractionate the protein component from a biological sample, while directly extracting diazepam and the major metabolites N-desmethyldiazepam, oxazepam and temazepam, and overcame the present disadvantages of direct sampling in biological matrices by SPME. The devices were interfaced with an LC-MS system and an isocratic mobile phase was used to desorb, separate, and quantify the analytes. The calculated diazepam, nordiazepam, temazepam, and oxazepam detection limits were 20, 20, 30, and 35 ng/ml in heparinized blood, respectively. The method was confirmed to be linear over the range of 50-1000 ng/ml with an average linear coefficient (R2) value of 0.996. The injection repeatability and intra-assay precision of the method were evaluated over ten injections at concentrations of 50, 200, and 500 ng/ml, resulting in a R.S.D. of ca. 10%. The robustness of the ADS-SPME device was evaluated for future use in in vivo studies, providing many direct extractions and subsequent determination of benzodiazepines in blood. For the extraction of the peptides angiotensin I, II, and III from blood, a novel restricted access material with cation exchange properties was evaluated. The ion-exchange diol silica improved the extraction efficiency of peptides relative to the conventional ADS material with reversed phase extraction centers.

Chromatography, High Pressure Liquid↗

PubMed2005

Poly(acrylamide-vinylpyridine-N,N'-methylene bisacrylamide) monolithic capillary for in-tube solid-phase microextraction coupled to high performance liquid chromatography.

In-tube solid-phase microextraction (SPME) based on a poly(acrylamide-vinylpyridine-N,N'-methylene bisacrylamide) monolithic capillary was investigated and on-line coupled to HPLC for the determination of trace analytes in aqueous samples. The polymer monolith was conveniently synthesized in a fused silica capillary by in situ polymerization method. Several groups of analytes including non-steroidal anti-inflammatory drugs, phenols, non-peptide angiotensin II receptor antagonists and endocrine disrupting chemicals were extracted by the monolithic capillary. High extraction efficiency was achieved for the analytes investigated and great improvement of the limits of detection were obtained in comparison to that of direct chromatographic analysis and strong hydrophobic and ion-exchange interactions between the analytes and the polymer were confirmed. The newly developed monolithic capillary showed excellent reusability and high stability under extreme pH conditions during extraction. The possibility of applying the established method to water sample analysis was also demonstrated.

Chromatography, High Pressure Liquid↗

PubMed2006

Multivariate optimization of the factors influencing the solid-phase microextraction of pyrethroid pesticides in water.

A method based on solid-phase microextraction (SPME) and gas chromatography with micro-electron capture detection (GC-microECD) has been optimized for the analysis of pyrethroids in water samples. The influence of parameters such as temperature, fibre coating, salting-out effect and sampling mode on the extraction efficiency has been studied by means of a mix-level factorial design, which allowed the study of main effects as well as two factor interactions. Finally, a method based on direct SPME at 50 degrees C, using polydimethylsiloxane fibre is proposed. The method showed good linearity (R2>0.995) and repeatability (RSD<or=16%) for all compounds, with detection limits ranging from 0.05 pg/mL for transfluthrin to 2.18 pg/mL for permethrin, and in general <or=1 pg/mL for most pyrethroids. Reliability was demonstrated through the evaluation of the recoveries in different water samples, such as tap water, groundwater, river water, runoff water, and wastewater. These studies demonstrated the validity of external standard calibration to quantify the target compounds in real samples, including a simple dilution step for the most complex matrices, which notoriously simplifies quantification by SPME.

Chromatography, Gas↗

PubMed2000

Solid-phase microextraction: a promising technique for sample preparation in environmental analysis.

Solid-phase microextraction (SPME) is a simple and effective adsorption and desorption technique, which eliminates the need for solvents or complicated apparatus, for concentrating volatile or nonvolatile compounds in liquid samples or headspace. SPME is compatible with analyte separation and detection by gas chromatography and high-performance liquid chromatography, and provides linear results for wide concentrations of analytes. By controlling the polarity and thickness of the coating on the fibre, maintaining consistent sampling time, and adjusting other extraction parameters, an analyst can ensure highly consistent, quantifiable results for low concentration analytes. To date, about 400 articles on SPME have been published in different fields, including environment (water, soil, air), food, natural products, pharmaceuticals, biology, toxicology, forensics and theory. As the scope of SPME grew, new improvements were made with the appearance of new coatings that allowed an increase in the specificity of this extraction technique. The key part of the SPME fibre is of course the fibre coating. At the moment, 27 variations of fibre coating and size are available. Among the newest are a fibre assembly with a dual coating of divinylbenzene and Carboxen suspended in poly(dimethylsiloxane), and a series of 23 gauge fibres intended for specific septumless injection system. The growth of SPME is also reflected in the expanding number of the accessories that make the technology even easier to use Also available is a portable field sampler which is a self-contained unit that stores the SPME fibre after sampling and during the shipment to the laboratory. Several scientific publications show the results obtained in inter-laboratory validation studies in which SPME was applied to determine the presence of different organic compounds at ppt levels, which demonstrates the reliability of this extraction technique for quantitative analysis.

Chromatography, Gas↗

PubMed2000

Characterisation of whiskeys using solid-phase microextraction with gas chromatography-mass spectrometry.

The application of solid-phase microextraction and gas chromatography-mass spectrometry to the detection of flavour volatiles present in Irish and Scottish whiskeys was investigated. A method was developed to characterise these volatiles which included the extraction, identification and quantification of 17 congeners which included fusel alcohols, acetates and esters. The method validation produced the optimum fibre [85 microm poly(acrylate)], extraction time (35 min), sample volume size (3 ml) and desorption time (5 min). The impact of salt on the absorption process was also studied. Characteristic profiles were determined for each whiskey and the flavour congeners were quantified using 4-methyl-2-pentanol as the internal standard. Calibration ranges were determined for each of the congeners with coefficients of linearity ranging from 0.993 (butan-1-ol) to 0.999 (ethyl laurate) and relative standard deviations ranging from 2.5% (2-methylbutan-1-ol) to 21% (furfural) at a concentration of 18.2 mg/l. Detection limits ranged from 0.1 mg/l (ethyl caprate) to 21 mg/l (butan-2-ol).

Alcoholic Beverages↗

PubMed2000

Solid-phase microextraction for organochlorine pesticide residues analysis in Chinese herbal formulations.

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to determine pesticide residues in Chinese herbal formulations. Fibers coated with a 100-microm film thickness of poly(dimethylsiloxane) was used to extract 19 organochlorine pesticides (OCPs). The pesticides in the study consisted of alpha-, beta-, gamma-and delta-hexachlorocyclohexane, p,p'-DDD, p,p'-DDE, p,p'-DDT, o,p'-DDT, aldrin, dieldrin, endrin, endrin aldehyde, endrin ketone, endosulfan (I, II and sulfate), heptachlor, heptachlor epoxide, and methoxychlor. The optimal experimental procedures for the adsorption and desorption of pesticides were evaluated. The linearity was obtained with a precision below 11% RSD for the studied pesticides expect endosulfan sulfate (21%) in a wide range from 1 to 200 ng/g. Detection limits were reached at below ng/g levels. Heptachlor epoxide was determined at a calculated limit of 0.03 ng/g. Comparison between SPME and Soxhlet extraction showed that SPME has a less than one order detection limit for residue pesticide determination. The proposed method was tested by analyzing herbal formulations from a local market for OCP multiresidues. Some residues studied were detected in the analyzed samples. The results demonstrate the suitability of the SPME-GC-MS approach for the analysis of multi-residue OCPs in Chinese herbal formulations.

Drugs, Chinese Herbal↗

PubMed2002

Headspace solid-phase microextraction analysis of aroma compounds in vinegar. Validation study.

Headspace solid-phase microextraction (HS-SPME) was evaluated for analysing aromatic compounds in vinegar. The fibre used (a Carboxen-polydimethylsiloxane fibre), and the analytical conditions had been optimised in a previous work. The HS-SPME procedure developed shows detection and quantitation limits, and linear ranges adequate for analysing this type of compounds. The recoveries obtained were close to 100%, with repeatability values lower than 20%. However, considerable differences have been detected between different fibres. The method was applied to a variety of Sherry wine vinegars.

Acetic Acid↗

PubMed2003

Systematic error in automated in-tube solid-phase microextraction.

The widely employed configuration for automated in-tube solid-phase microextraction (SPME) involves modification of a commercial liquid chromatographic autosampler into an automated extraction device. This popular configuration is demonstrated to result in an inherent systematic error in the quantitation of analyte in a given matrix. The source of error is traced to the accumulation of analyte in the extraction and the pre-extraction segment (i.e., sample loop, metering valve and tubing prior to the metering valve) of the autosampler where the analyte comes in contact with the residual mobile phase. This results in cross-contamination due to sample/mobile phase mixing. The quantity of analyte accumulated in these segments is shown to consistently increase with the increasing number of draw/eject cycles. As a result of the accumulation, the amount of analyte recorded leads to inaccurate quantitative information, leading to overestimation of the limit of detection and limit of quantitation, when automated in-tube SPME is employed as an approach for sample enrichment. Insertion of a 100-microl air plug prior to extraction step was able to significantly minimize sample/mobile phase mixing of analyte with the residual mobile phase in the pre-extraction and extraction step, thus minimizing the systematic error.

Automation↗

PubMed2003

Optimisation of headspace solid-phase microextraction for the analysis of volatile phenols in wine.

Headspace solid-phase microextraction has been applied to the analysis of volatile phenols in wine. Silica fibre coated with Carbowax-divinylbenzene was found to be more efficient at extracting these compounds than other fibres such as those coated with polydimethylsiloxane, polyacrylate, carboxen-polydimethylsiloxane, and polydimethylsiloxane-divinylbenzene. Different parameters such as extraction time, temperature of the sample during the extraction, ionic strength and sample volume were optimised using a two-level factorial design expanded further to a central composite design, in order to evaluate several possibly influential and/or interacting factors. The headspace (HS)-SPME procedure developed shows adequate detection and quantitation limits, and linear ranges for correctly analysing these compounds in wine. The recoveries obtained were close to 100%, with repeatability values lower than 16%. The method was applied to a variety of white and red wines.

Chromatography, Gas↗

PubMed1997

Determination of barbiturates by solid-phase microextraction (SPME) and ion trap gas chromatography-mass spectrometry.

Solid-phase microextraction (SPME) in conjunction with quadrupole ion trap GC-MS was applied to the determination of a series of barbiturates. A 65 microns Carbowax-divinylbenzene (DVB) SPME fiber was used to successfully extract a series of eight barbiturates from aqueous solution. Absorption kinetics and distribution coefficients for the 65 microns Carbowax-DVB SPME fiber were determined for the compounds. In addition the method was evaluated with respect to linearity, limit of detection, precision, desorption time, and the effect of salt. Limits of detection reached 1 ng/ml for the barbiturates. Linearity was established for the barbiturates over a concentration range of 10-1000 ng/ml, with coefficients of correlation 0.99. Overall, the precision of the method fell between 2.2%-6.5%, depending on the barbiturate. SPME was applied to the identification and quantitation of the barbiturates in a urine matrix. The method was validated by analyzing a reference standard pentobarbital-spiked urine sample. Both standard addition and internal standard with [2H5]-pentobarbital techniques were evaluated, with recoveries found to be 93% and 104%, respectively SPME was then used to rapidly screen a urine specimen tested positive for barbiturates, and butalbital was detected and quantified.

Absorption↗

PubMed1997

Rapid semi-quantitative estimation of N-nitrosodibutylamine and N-nitrosodibenzylamine in smoked hams by solid-phase microextraction followed by gas chromatography-thermal energy analysis.

A solid-phase microextraction (SPME) analytical method has been developed for the determination of N-nitrosodi-n-butylamine (NDBA) and N-nitrosodibenzylamine (NDBzA) in hams that is based on: (a) isolation of the compounds by steam distillation, (b) SPME from the distillate headspace using a polyacrylate coated silica fibre and (c) determination by gas chromatography-thermal energy analyzer technique or confirmation by gas chromatography-mass spectrometry. Recoveries of both NDBA and NDBzA from hams spiked at 5 to 160 micrograms/kg levels ranged between 41 to 112%. The overall method is fast, sensitive (detection limits, 1 to 3 micrograms/kg), precise (within 10%) and fairly accurate (average recoveries 86% and 70%, respectively). The results obtained by this technique for seven ham samples agreed fairly well with those obtained by an existing method (r2 = 0.97). The new method is solventless, environmentally friendly and useful for rapid monitoring purposes.

Animals↗

PubMed2000

Use of solid-phase microextraction in the investigation of chemical communication in social wasps.

Solid-phase microextraction has been used to investigate chemical communication in several social wasp species. Using the technique to analyse exocrine gland secretions, we demonstrate that the results are comparable with those obtained with the more classical methods that use solvents, eliminating, in many cases, the shortcomings of these methods in insect pheromone analysis. As a result of its simplicity this technique is very suitable for research on the chemical ecology of social wasps, and on insect communication in general.

Animal Communication↗

PubMed2001

Determination of acrolein by headspace solid-phase microextraction gas chromatography and mass spectrometry.

We developed a headspace solid-phase microextraction (headspace SPME) method to measure acrolein in human urine. This new technique resolves some problems with the headspace gas chromatography and mass spectrometry (GC-MS) method which we developed previously. With the original method, a column and a filament were damaged by the injection of air. A 0.5-ml urine (or phosphate-buffered saline) sample in a glass vial containing propionaldehyde as an internal standard was heated for 5 min. The SPME fiber (65 microm carbonwax-divinylbenzene fiber) was exposed to the headspace and then inserted into a GC-MS instrument in which a DB-WAX capillary column (30 m x 0.32 mm, film thickness 0.5 degrees m) was installed. The total analysis time was 15 min. The inter-assay and intra-assay coefficients of variation were 10.07 and 5.79%, respectively. The calibration curve demonstrated good linearity throughout concentrations ranging from 1 to 10,000 nM. The headspace SPME method exhibits high sensitivity and requires a short analysis time as well as the previous method. We conclude that this method is useful to measure urinary acrolein.

Acrolein↗

PubMed2000

Use of headspace solid-phase microextraction (HS-SPME) in hair analysis for organic compounds.

Headspace solid phase microextraction (HS-SPME) has advantages of high purity of the extract, avoidance of organic solvents and simple technical manipulation and can be used in combination with gas chromatography-mass spectrometry (GC-MS) in the hair analysis of a number of drugs. HS-SPME coupled with the hydrolysis of the hair matrix by 4% sodium hydroxide in the presence of excess sodium sulphate and of a suitable internal standard proved to be a convenient one-step method for the measurement of many lipophilic basic drugs such as nicotine, amphetamine derivatives, local anaesthetics, phencyclidine, ketamine, methadone, diphenhydramine, tramadol, tricyclic antidepressants and phenothiazines. Detection limits were between 0.05 and 1.0 ng/mg. From spiked 10-mg hair samples absolute recoveries between 0.04 and 5.7% were found. These recoveries decreased considerably if larger sample amounts were used, perhaps due to increased drug solubility in the aqueous phase or to elevated viscosity in the presence of dissolved hair proteins. Because of the phenolic hydroxyl group a change of pH after alkaline hair digestion (by adding excess orthophosphoric acid) was necessary for the detection of delta 9-tetrahydrocannabinol (delta 9-THC), cannabinol (CBN) and cannabidiol (CBD) by HS-SPME. Nevertheless, the detection limits were such that only CBN could be detected in hair of a consumer. Clomethiazole, a compound hydrolysed in alkali, was measured by HS-SPME after extraction with aqueous buffer. The detection limit was 0.5 ng/mg. Cocaine could not be detected by HS-SPME. The application of HS-SPME to hair samples from several forensic and clinical cases is described.

Antidepressive Agents, Tricyclic↗

PubMed2000

Shelf-life prediction of processed milk by solid-phase microextraction, mass spectrometry, and multivariate analysis.

A technique based on solid-phase microextraction, mass spectrometry, and multivariate analysis (SPME-MS-MVA) was used to predict the shelf life of pasteurized and homogenized reduced-fat milk and whole-fat chocolate milk sampled over a 7 month period. Using SPME-MS-MVA, which is essentially a mass spectrometry-based electronic-nose instrument, volatile bacterial metabolites were extracted from milk with SPME (Carboxen-PDMS) and injected into a GC capillary column at elevated temperature. Mass fragmentation profiles from the unresolved milk volatile components were normalized to the intensity of a chlorobenzene internal standard mass peak (m/z 112) and subjected to MVA. Prediction models based on partial least-squares regression of mass intensity lists were able to predict the shelf life of samples to approximately +/-1 day, with correlation coefficients greater than 0.98 for the two types of milk samples. Using principal component analysis techniques, the procedure was also useful for classifying samples that were rendered unpalatable by nonmicrobial sources (contamination by copper and sanitizer) as well as by bacteria.

Animals↗

PubMed2000

Analysis of the volatile components in vanilla extracts and flavorings by solid-phase microextraction and gas chromatography.

The development and application of a solid-phase microextraction (SPME) method in the analysis of vanilla extracts and vanilla flavorings was studied. The SPME method was developed to be used in conjunction with gas chromatography mass spectrometry (GC-MS). The optimized SPME sampling parameters for the determination of the volatile components included a poly(acrylate) fiber, a 40-min sampling time at room temperature, and a 2-min desorption time. The reproducibility of the method was good, with a percent relative standard deviation between 2.5 and 6.4% for the target compounds. The data suggest that the origin of natural extracts can be readily determined from the GC profile and that differences exist between nature-identical and synthetic flavorings and the natural extracts. The method also has potential for identifying the type of vanilla extract/flavoring used to flavor food.

Flavoring Agents↗