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Results for “Solid Phase Microextraction”

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At least 73 records · Page 4Linked to original sources

PubMed2003

Time-weighted average passive sampling with a solid-phase microextraction device.

A modified Solid-Phase Microextraction (SPME) device has been used as a passive sampler to determine the time-weighted average (TWA) concentration of volatile organic compounds (VOCs) in air. Unlike conventional sampling with SPME, in which the fiber is extended outside its needle housing, during TWA passive sampling, the fiber is retracted a known distance into its needle housing. The SPME passive sampler collects the VOCs by the mechanism of molecular diffusion and sorption on to a coated fiber as collection medium. This process has been shown to be described by Fick's first law of diffusion, whereby determination of the amounts of analytes accumulated over time enable measurement of the TWA concentration to which the sampler was exposed. A series of fibers, 100-microm poly(dimethylsiloxane), 65-microm poly(dimethylsiloxane)/divinylbenzene, and 75-microm Carboxen/poly(dimethylsiloxane), were tested for their "zero sink", face velocity, and response time behavior. Of the fibers tested, that coated with 75-microm Carboxen/poly(dimethylsiloxane) was found to be an excellent passive sampler for VOCs. TWA passive sampling with a SPME device was shown to be almost independent of face velocity and to be more tolerant of high and low analyte concentrations and long and short sampling times, because of the ease with which the diffusion path length could be changed. It was found that environmental conditions, e.g., temperature, pressure, relative humidity, and ozone, have little or no effect on sampling. The 75-microm Carboxen/poly(dimethylsiloxane) fiber can retain VOCs for up to two weeks without significant loss. When the SPME device was tested in the field and the results were compared with those from National Institute of Occupational Health and Safety method 1501, good agreement was obtained.

Air Pollutants, Occupational↗

PubMed2004

Tequila volatile characterization and ethyl ester determination by solid phase microextraction gas chromatography/mass spectrometry analysis.

Solid phase microextraction (SPME) and gas chromatography were used for tequila volatile characterization and ethyl ester quantitation. Several factors determined the differences in tequila volatile profiles obtained by the SPME technique, namely, sampling mode, fiber coating, and fiber exposure time. Each of these factors determined the most suitable conditions for the analysis of volatile profiles in tequila. Volatile extraction consisted of placing 40 mL of tequila in a sealed vial kept at 40 degrees C. A poly(dimethylsiloxane) fiber was immersed in the liquid for 60 min and desorbed for 5 min into the gas chromatograph. The identified volatiles by mass spectrometry were mainly alcohols, esters, and ketones. The calibration curves for ethyl hexanoate, octanoate, and decanoate followed linear relationships with highly significant (p < 0.001) determination coefficients (R2 = 0.99). The coefficients of variation of less than 10% for ethyl ester concentrations indicated that the technique was reproducible. The limits of quantitation for ethyl esters were 0.05 parts per million, which were below the concentration range (0.27-15.03 ppm) found for different tequila samples. Quantitative differences in ethyl esters were found for the four most commonly known tequila types: silver, gold, aged, and extra-aged.

Alcoholic Beverages↗

PubMed2006

Online coupling of solid-phase microextraction and capillary electrophoresis.

Solid-phase microextraction (SPME) and capillary electrophoresis (CE) are two of the main inventions that shaped 20th Century analytical chemistry. SPME is an effective microscale sampling and sample preparation technique, and CE is a high-efficiency microanalytical method. Online coupling of SPME with CE can be a powerful combination because of the significant advantages of the two techniques. The progress in the development of online SPME-CE coupling is surveyed in this review. Problems encountered and solutions reported are highlighted.

Journal Article↗

PubMed1999

[Determination of 2,4-dinitrophenol by solid-phase microextraction coupled to GC/MS].

Solid-phase microextraction coupled GC/MS was investigated for the determination of 2,4-dinitrophenol in aqueous sample. Analytes were extracted by a 85 microns polyacrylate coated fiber. The fiber was then transferred into the injector of GC. Analytes were thermally desorbed and detected by GC/MS. The influences of several parameters on SPME procedure have been studied. The optimization condition was obtained: directly sampling in the water sample with the extraction period was 30 min and the desorption time 3 min at 270 degrees C. Acidification by hydrochloric acid (pH 2) and saturated salt were necessary for the best sensitivity. The precision of SPME is better than that of liquid-liquid extraction. This method is a fast, simple, and pre-concentration-free technique, which is suitable for detecting 2,4-dinitrophenol in water sample.

2,4-Dinitrophenol↗

PubMed2004

[Characteristics and applications of amide bridged calix [ 4 ] arene solid-phase microextraction fiber].

A novel solid-phase microextraction (SPME) fiber coated with 25,27-dihydroxy-26, 28-(1', 10'-dioxa-4', 7'-diaza-3', 8'-dioxooctylene ) -p-tert-butylcalix [ 4 ] arene/hydroxy-terminated silicone oil (amide bridged -C[4]/OH-TSO) was prepared with sol-gel technology and applied to the analysis of aliphatic amines and aromatic amines without derivatization. It demonstrated high thermal stability of up to 380 degrees C and stability in organic and inorganic solvents, a prolonged lifetime of over 200 times for headspace SPME, great fiber-to-fiber reproducibility with a relative standard deviation (RSD) of no more than 6.3% for aromatic amines, etc. Due to the introduction of polar amide bridge in calixarene molecules, polarity of the coating increases and thus the fiber shows better extraction efficiency in most of the investigated aliphatic amines and aromatic amines compared to the extraction efficiency of commercial fibers, indicating specific selectivity and sensitivity to amines. The detection limits (LODs) were determined to be 0.19 - 39.51 microg/L, the linear ranges were 3 orders of magnitude with a precision better than 5.1% for aliphatic amines, and they were 1.21 - 40.73 ng/L, 4 - 6 orders of magnitude with a precision better than 6.0% for aromatic amines. The application of this SPME technique coupled with gas chromatography has been shown to be feasible for the rapid determination of fish freshness.

Amines↗

PubMed2006

Fast and sensitive method to determine chloroanisoles in cork using an internally cooled solid-phase microextraction fiber.

A new generation of solid-phase microextraction (SPME) fiber, an internally cooled fiber (cold fiber with polydimethylsiloxane loading) that allows heating the sample matrix and simultaneously cooling the fiber coating, was used to determine 2,4-dichloroanisole, 2,6-dichloroanisole, 2,4,6-trichloroanisole and pentachloroanisole in cork. A comparison between the cold fiber and regular SPME fiber was performed. An automated headspace solid-phase microextraction (HS-SPME) using commercial fibers and an internally cooled SPME fiber (CF-HS-SPME) coupled to gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) was used. The extraction conditions for both CF-HS-SPME and HS-SPME were optimized using full factorial design and Doehlert matrix. The best extraction conditions for CF-HS-SPME were obtained using 10 min of incubation time, 10 min of extraction time, and sample and fiber temperature of 130 and 10 degrees C, respectively. For HS-SPME, polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used with 10 min of incubation time, 75 min of extraction time, 85 degrees C of sample temperature, 8 ml of water was added and agitated at 500 rpm. The quantification limits for the target compounds using CF-HS-SPME procedure were between 0.8 and 1.6 ng g(-1) of cork, while for HS-SPME were between 4 and 6 ng g(-1) of cork. Furthermore, the CF-HS-SPME procedure could be used as a non-destructive method after minor modification of the agitator for the autosampler.

Anisoles↗

PubMed2004

[Applications of solid-phase microextraction technique in natural product analysis].

Solid-phase microextraction is a new technique of analysis. It has many merits and expanse foreground. A Review of the principle, recent development and applications of solid-phase microextraction is given, focusing on natural product analysis, especially on Chinese traditional medicine. Twenty-nine references are cited in the paper.

Animals↗

PubMed2006

Progress of solid-phase microextraction coatings and coating techniques.

Solid-phase microextraction (SPME) has been popular as an environmentally friendly sample pretreatment technique to extract a very wide range of analytes. This is partly owing to the development of SPME coatings. One of the key factors affecting the extraction performances, such as the sensitivity, selectivity, and reproducibility, is the properties of the coatings on SPME fibers. This paper classifies the materials used as SPME coatings and introduces some common preparation techniques of SPME coating in detail, such as sol-gel technique, electrochemical polymerization technique, particle direct pasting technique, restricted access matrix SPME technique, and molecularly imprinted SPME technique.

Cellulose↗

PubMed2001

[Advances in solid phase microextraction coupled with high performance liquid chromatography].

Solid phase microextraction (SPME) is a solvent-free technique with high extraction efficiency and easy to perform automatically. It can be coupled with high performance liquid chromatography to perform efficient analysis of compounds with high polarity. The advances in solid phase microextraction coupled with high performance liquid chromatography, including its theory, interfaces, coating materials and applications, are reviewed with 36 references.

Chromatography, Gas↗

PubMed2004

Studies on the aroma of cupuassu liquor by headspace solid-phase microextraction and gas chromatography.

Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography with ion trap mass spectrometric detection and with atomic emission detection (GC-AED) was employed to identify possible odor-impact volatile organic compounds in cupuassu (Theobroma grandiflorum Spreng) liquor, as well as to quantify alkylpyrazines present in these samples. SPME fibers coated with 100 microm polydimethylsiloxane (PDMS), 65 microm PDMS-divinylbenzene (DVB) and 75 microm Carboxen (CAR)-PDMS were tested, the later being chosen for the optimized extraction procedure. The principal compounds found in the sample headspace were 3-methylbutanal, dimethylsulfide, dimethyldisulfide, beta-linalool and several alkylpyrazines (notably tetramethylpyrazine). The procedure for quantitation of the alkylpyrazines, using GC-AED for their separation and detection, allowed the detection of microg g(-1) levels of the analytes in the samples, with acceptable precision (R.S.D. less than 10%).

Chromatography, Gas↗

PubMed2004

Determination of the immunosuppressant mycophenolic acid in human serum by solid-phase microextraction coupled to liquid chromatography.

A solid phase microextraction (SPME)-HPLC-UV method for the determination of the immunosuppressant mycophenolic acid (MPA) in human serum samples was developed for the first time. The procedure, that employed a carbowax/templated resin (Carbowax/TPR-100) as fiber coating, required a very simple sample pretreatment, an isocratic elution, and provides an highly selective extraction. The linear range was 0.2-100 microg x ml(-1). Recovery was practically unchanged (63+/- 4%) passing from 0.2 to 100 microg x ml(-1) level. Within-day and between-days coefficient of variation ranged from 5.9 to 6.5% and from 8.8 to 9.2%, respectively. A detection limit of 0.05 microg x ml(-1) was estimated in spiked serum. The method was successfully applied to the determination of MPA in serum of a patient under mycophenolate mophetil ester (MMF) therapy, as demonstrated by the relevant concentration-time profiles.

Chromatography, High Pressure Liquid↗

PubMed2000

Indirect analysis of urea herbicides from environmental water using solid-phase microextraction.

We described here a solid-phase microextraction procedure used to extract six urea pesticides-- chlorsulfuron, fluometuron, isoproturon, linuron, metobromuron and monuron--from environmental samples. Two polydimethylsiloxanes and a polyacrylate fiber (PA) are compared. The extraction time, pH control, addition of NaCl to the water and the influence of organic matter such as humic acid on extraction efficiency were examined to achieve a sensitive method. Determination was carried out by gas chromatography with nitrogen-phosphorus detection. The proposed method requires the extraction of 2 ml of sample (pH 4, 14.3%, w/v, NaCl) for 60 min with the PA fiber. The limits of detection range from 0.04 for linuron to 0.1 microg/l for fluometuron and monuron and the relative standard deviations at the 1 microg/l level are between 15% and 9%. The apparent fiber-water distribution constants (Kfw) calculated in the proposed conditions were in the order of 10(3). Phenylurea herbicides were indirectly determined in the form of their derived anilines and chlorsulfuron in the form of an aminotriazine as confirmed by gas chromatography-mass spectrometry. Natural waters were utilized to validate the final procedure. However, a unequivocal identification in unknown environmental samples should be done by LC-MS. The presence of dissolved organic matter such as humic acid produces losses during the extraction step. Adding sodium chloride to the sample compensates for this effect.

Herbicides↗

PubMed2001

Determination of organophosphorus pesticides in honeybees after solid-phase microextraction.

A method based on solid-phase microextraction (SPME) followed by gas chromatography with nitrogen-phosphorus detection was developed for the purpose of determining 18 organophosphorus pesticide residues in honeybee samples (Apis mellifera). The extraction capacities of polyacrylate and poly(dimethylsiloxane) fibers were compared. The main factors affecting the SPME process, such as the absorption time profile, salt, and temperature, were optimized. The method involved honeybee sample homogenization, elution with an acetone:water solution (1:1) and dilution in water prior to fiber extraction. Moreover, the matrix effect on the extraction was evaluated. In samples spiked at the 0.2 mg kg(-1) level, the coefficient variation was between 1 and 13% and the detection limits were below 10 microg kg(-1). The SPME procedure was found to be quicker and more cost-effective than the solvent extraction method commonly used. The method was applied successfully to environmental screening. Parathion methyl was detected and confirmed in the real samples analyzed.

Animals↗

PubMed2001

Solid-phase microextraction of phthalates from water.

Solid-phase microextraction (SPME) with six different non-polar and polar fibres was used to extract seven phthalate esters from water samples for analysis by gas chromatography-mass spectrometry. With regard to extraction efficiency and repeatability of the extractions, the 70-microm Carbowax-divinylbenzene fibre was especially suitable for the selected phthalates with water solubilities between 4200 mg l(-1) (dimethyl phthalate) and 0.0003 mg l(-1) (di-n-octyl phthalate). Linearity was controlled in the range between 0.02 and 10 microg l(-1). In analysed drinking water samples from Leipzig (Germany) and Katowice (Poland) four of the investigated phthalates [diethyl phthalate, di-n-butyl phthalate, butylbenzyl phthalate and di(2-ethylhexyl) phthalate] were found to be present in concentrations between 0.02 and 0.6 microg 1(-1).

Calibration↗

PubMed2002

Dynamic versus static sampling for the quantitative analysis of volatile organic compounds in air with polydimethylsiloxane-carboxen solid-phase microextraction fibers.

Polydimethylsiloxane-Carboxen solid-phase microextraction fibers are now well known to be very efficient trapping media for the analysis of volatile organic compound (VOC) traces in air. However, competitive adsorption, due to the nature of the coating, considerably limits analyte quantitation. In this contribution, different experimental conditions are investigated to achieve quantitative analysis. Static and dynamic sampling were compared for the analysis of 11 VOCs in a standard gaseous mixture at different extraction times (1, 5, 15 and 45 min). The same experiments were performed with four isolated compounds. Adsorption results from gas mixture and isolated compounds were compared and a common linear range (i.e., where quantitative analysis is conceivable) was determined. When sampling was in the dynamic mode, compounds with lower affinity for the coating showed a very narrow linear range, meaning that competition for adsorption was quickly discriminative. The same experiments in static mode allowed one to obtain wider linear ranges for all compounds, especially for lower-affinity compounds: for a 1 min sampling time, acetone showed a linear adsorption range from 3 to 60 microg m(-3) in the dynamic mode which extended from 5 to 300 microg m(-3) in the static mode.

Air↗

PubMed2002

Determination of esters in dry and sweet white wines by headspace solid-phase microextraction and gas chromatography.

Headspace solid-phase microextraction (HS-SPME) was studied for the high-resolution gas chromatographic (HRGC) analysis of esters in wines. Five different SPME fibers were tested and the influence of different factors such as temperature and time of desorption, extraction time, extraction technique, stirring, sample and vial volume, sugar and ethanol content were studied and optimised using model solutions. The proposed HS-SPME-GC method is an appropriate technique for the quantitative analysis of esters in dry and sweet white wines.

Calibration↗

PubMed2003

Determination of major compounds in sweet wines by headspace solid-phase microextraction and gas chromatography.

Headspace solid-phase microextraction (HS-SPME) was studied by high resolution gas chromatographic analysis of major compounds (ethyl acetate, methanol, 1-butanol, 2-butanol, 1-propanol, isobutanol, 2-methyl-1-butanol and 3-methyl-1-butanol) in sweet wines. Five different SPME fibres were tested and the influence of different factors such as temperature and time of desorption, extraction time, stirring, sample and vial volume, sugar and ethanol content were studied and optimized using model solutions. The SPME method was validated with the direct injection method. The proposed HS-SPME-GC method is an appropriate technique for the quantitative analysis of the mentioned analytes in real sweet wines.

Acetates↗

PubMed2001

Determination of hydrocarbons in old creosote contaminated soil using headspace solid phase microextraction and GC-MS.

Headspace solid phase microextraction (HS-SPME) has been used together with GC-MS to analyze organic substances directly in a soil, heavily contaminated with PAHs/creosote (approximately 300 mg/kg soil), from an old gaswork site in Stockholm, Sweden. The HS-SPME results, both qualitative and quantitative, were compared with traditional liquid extraction using ethyl acetate/hexane (20:80). It was shown that the concentrations determined with HS-SPME at 60 degrees C correlated well, for compounds containing up to two and three aromatic rings (naphthalenes, acenaphthene, acenaphthylene and fluorenes, while a lower concentration was obtained for phenanthrene, anthracene, fluoranthene and pyrene. The total concentrations for each compound determined with HS-SPME ranged from 2 to 25 microg/g soil. Quantification was done using standard addition of compounds directly to the soil samples. The bioavailable fraction of the compounds in the contaminated soil at 20 degrees C was analyzed using external calibration by spiking sterile uncontaminated sand (same texture and particle size as the contaminated soil but without a heavily sorbed organic fraction) with hydrocarbon standards in different concentrations. Storage of exposed fibers at 20 degrees C showed that analysis should be done within two days to make qualitative measurements and earlier (as soon as possible) for quantitative determinations.

Biological Availability↗