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Results for “Solid Phase Microextraction”

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PubMed2002

Truffle aroma analysis by headspace solid phase microextraction.

An experimental design has been used to optimize the extraction of volatile compounds from summer truffle aroma (Tuber aestivum) by using headspace solid phase microextraction. The extracted compounds have been analyzed by gas chromatography with a flame ionization detector and by gas chromatography-mass spectrometry (GC-MS). In an attempt to develop an objective method to fully characterize truffle aroma, a fiber of medium polarity (for flavors) was used to avoid discrimination toward very nonpolar and polar volatile compounds. To optimize the extraction conditions, a response surface experimental design was applied considering three factors such as extraction temperature, equilibrium time, and extraction time. From the statistical analysis of the experimental design, it was possible to determine that the most important factor influencing the abundance of aroma compounds was the extraction temperature. Optimal extraction temperature was established at approximately 50 degrees C. By using GC-MS, it was possible to identify 37 compounds, most of them previously described as responsible for truffle aroma.

Ascomycota↗

PubMed2001

Applications of solid-phase microextraction (SPME) in the determination of residues of certain herbicides at trace levels in environmental samples.

A new analytical procedure based on solid-phase microextraction (SPME) has been developed for the determination of residues of eight selected herbicides: trifluralin, butachlor, pretilachlor, metolachlor, atrazine, acetochlor, alachlor, and fluroxypyr-meptyl, in ground water samples. Carbowax divinylbenzene was used for SPME of the herbicides. Quantification was done at equilibrium. Various parameters, such as, effect of pH, ionic strength, humic acid content and exposure time of fiber, were investigated to find the extraction efficiency. The linearity was determined. The method was found suitable for the determination of residues of herbicides at concentration levels from 5 to 20 ng L-1. The relative standard deviation of the detection limits were calculated. The humic acid content was found to interfere more significantly in the determination of residues. An ionic chloride strength, in terms of sodium chloride, of up to 10% did not have any significant impact on the determination. Furthermore, there was an enhanced sensitivity of detection up to pH 3.0. The method was applied to the analysis of the residue contents of the pesticides under investigation in real ground water samples collected from susceptible places. The results when compared with the standard methods published in the literature showed no significant deviation in their quantification and the values were comparable.

Chemistry Techniques, Analytical↗

PubMed2000

[Analysis of headspace constituents of Gardenia flower by GC/MS with solid-phase microextraction and dynamic headspace sampling].

The headspace constituents of fresh Gardenia flower were investigated by GC/MS. The headspace volatiles were sampled by solid-phase microextraction (SPME) and dynamic headspace sampling (DHS). SPME sampling was conducted with 100 microns PDMS fiber at 28 degrees C for 60 min. In DHS sampling, purified nitrogen was used as purging gas with a flow rate at 80 mL/min for 120 min. Tenax GR(20 mesh-40 mesh) was used as adsorbent and the volatiles were eluted by ether, and concentrated to 0.5 mL for GC/MS analysis. A Supelco-wax capillary column (30 m x 0.25 mm i.d. x 0.25 micron df) was employed in GC/MS analysis. Initial oven temperature was kept at 45 degrees C for 2 min, then raised to 250 degrees C at 4 degrees C/min, and kept at 250 degrees C for 10 min. According to SPME-GC/MS analysis, the main compounds in headspace of fresh Gardenia flower included farnesene(64.86%), cis-ocimene(29.33%), linalool(2.74%), cis-3-hexenyl tiglate(1.34%), methyl benzoate(0.25%). Results obtained from SPME and DHS sampling were also compared. In this study, SPME afforded a simpler and more sensitive sampling method, and much more accurate information about headspace volatiles of Gardenia flower.

Acyclic Monoterpenes↗

PubMed2006

[Preparation and characterization of chitosan membrane for solid phase microextraction technique].

Chitosan is a kind of natural polymers containing plenty of amido and hydoxy. The chitosan membrane is tough, and since the partition coefficient of chlorophyll between chitosan membrance and water is as high as 9,090, the chitosan membrane may beeasily manufactured as solid-phase microextraction membrane for the analysis of chlorophyll. The system may reach a complete equilibrium in 80 min. Then the membrane can be desorbed completely in 30 min in 5% NaOH with ultrasonic. Both IR and XRD indicated that hydrogen bonds between the molecules of chitosan were weakened and amido and hydoxy were considered as the keys during the process of extracting chlorophyll.

Chitosan↗

PubMed2006

Molecularly imprinted polymers for solid-phase extraction and solid-phase microextraction: recent developments and future trends.

Molecularly imprinted polymers (MIPs) are synthetic polymers having a predetermined selectivity for a given analyte, or group of structurally related compounds, that make them ideal materials to be used in separation processes. In this sense, during past years a huge amount of papers have been published dealing with the use of MIPs as sorbents in solid-phase extraction, namely molecularly imprinted solid-phase extraction (MISPE). Although the majority of these papers were restricted to describe the use of different templates for different applications, several attempts proposing new alternatives to minimize the inherent drawbacks of the preparation and use of MIPs (i.e. template bleeding, tedious synthesis procedure, etc.) have been reported. Thus, this paper does not pretend to be a collection of MISPE-related papers but to give an overview on the significant attempts carried out during recent years to improve the performance of MIPs in solid-phase extraction. In addition, the use of MIPs packed in high performance liquid chromatography (HPLC) columns for the direct injection of crude sample extracts and the preparation of imprinted fibres for solid-phase microextraction will be also discussed.

Combinatorial Chemistry Techniques↗

PubMed2004

Dynamic solid phase microextraction for sampling of airborne sarin with gas chromatography-mass spectrometry for rapid field detection and quantification.

A portable dynamic air sampler and solid phase microextraction were used to simultaneously detect, identify, and quantify airborne sarin with immediate analysis of samples using a field portable gas chromatography-mass spectrometry system. A mathematical model was used with knowledge of the mass of sarin trapped, linear air velocity past the exposed sampling fiber, and sample duration allowing calculation of concentration estimates. For organizations with suitable field portable instrumentation, these methods are potentially useful for rapid onsite detection and quantification of high concern analytes, either through direct environmental sampling or through sampling of air collected in bags.

Air↗

PubMed2003

Headspace solid-phase microextraction (HS-SPME): a microscale sampling technique for determination of monoterpene hydrocarbons in coniferous needles by gas chromatography/mass spectrometry (GC/MS).

A headspace solid-phase microextraction (HS-SPME) technique has been applied for the microscale sampling (single needle for Picea omorica, two needles of Picea abies) of volatile monoterpene hydrocarbons (MTHs) from conifer needles. A simple device consisting of a closed headspace vial equipped with an integral cutting device was used for the collection, homogenisation, and HS-SPME sampling. The highly sensitive gas chromatographic/mass spectrometric (GC/MS) analyses (LODs in tenths of ng g(-1) FW were obtained for 3xS/N criteria) of individual needles confirmed the space distribution of MTHs in different parts of a single sprout (base, centre, apex) and among the left, central and right sprout of a whorl. The highest concentrations of MTHs were found in the apical (leading) sprout (S) of a whorl. The serious increase of MTHs content near the base of the left (SNL) sprout and nearly zero concentrations in the central parts of both the side sprouts of P. abies corresponded to the morphology of the whorl. On the other hand, similar concentrations of MTHs were found in the apex of the side (SNL and SNR) sprouts. The distributions of MTHs obtained after HS-SPME and solvent extraction followed the similar trends for both species. HS-SPME is more suitable for the evaluation of distribution of volatiles in microscale experiments due to the more precise separation of needles into correct categories and elimination of "averaging" effects of the larger quantities of needles needed for the solvent extraction. The precision was improved by one order of magnitude due to the reduction of uncontrolled losses of volatile species during the sample treatment.

Gas Chromatography-Mass Spectrometry↗

PubMed2006

Optimization of solid-phase microextraction procedures for the determination of tricyclic antidepressants and anticonvulsants in plasma samples by liquid chromatography.

Simple, sensitive, and reproducible off-line solid-phase microextraction and liquid chromatography (SPME/LC) methods are described for the determination of seven anticonvulsants and tricyclic antidepressants in human plasma. Factorial design and simplex methodology were applied in the optimization of the SPME procedure for tricyclic antidepressants analyses. Important factors in the SPME efficiency are discussed, such as the fiber coatings (both lab-made and commercial), extraction time, pH, ionic strength, influence of plasma proteins, and desorption conditions. The development of the lab-made fiber coatings, namely, octadecylsilane, aminosilane, and polyurethane, are further described and applied to anticonvulsants analyses. The investigated plasmatic range for the evaluated anticonvulsants, using CW-TPR fiber, were the following: phenylethylmalonamide (3.00-40.0 microg mL(-1)), phenobarbital (5.00-40.0 microg mL(-1)), primidone (3.00-40.0 microg mL(-1)), carbamazepine and carbamazepine-epoxide (2.00-24.0 microg mL(-1)), phenytoin (2.00-40.0 microg mL(-1)), and lamotrigine (0.50-12.0 microg mL(-1)). The antidepressants' linear plasmatic concentration ranged from 75.0 to 500 ng mL(-1) for imipramine, amitriptyline, and desipramine, and from 50.0 to 500 ng mL(-1) for nortriptyline, being in all cases, the limit of quantification represented by the lowest value. The precision (interassays) for all investigated drugs in plasma sample spiked with different concentrations of each analyte and submitted to the described procedures were lower than 15%. The off-line SPME/LC methodologies developed allow anticonvulsants and antidepressants analyses from therapeutic to toxic levels for therapeutic drug monitoring.

Amitriptyline↗

PubMed2005

Impurity analysis of 1,4-dioxane in nonionic surfactants and cosmetics using headspace solid-phase microextraction coupled with gas chromatography and gas chromatography-mass spectrometry.

1,4-Dioxane impurity in nonionic surfactants and cosmetics were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Experimental results show that there is no significant difference using SPME-GC and SPME-GC-MS for analysis of 1,4-dioxane in three types of nonionic surfactants at the 95% confidence level. The relative standard deviation (R.S.D.) values of each analytical method were smaller than 3%. The amount of 1,4-dioxane was found to vary from 11.6 +/- 0.3 ppm to 73.5 +/- 0.5 ppm in 30% of nonionic surfactants from manufacturers in Taiwan. These methods were linear over the studied range of 3-150 ppm with correlation coefficients higher than 0.995. The recoveries of 1,4-dioxane for these nonionic surfactants following SPME were all higher than 96 +/- 1% (n = 3). The detection limits of 1,4-dioxane for these nonionic surfactants following SPME were from 0.06 ppm to 0.51 ppm. The experimentally determined level of 1,4-dioxane in cosmetics from manufacturers in Taiwan varied from 4.2 +/- 0.1 ppm to 41.1 +/- 0.6 ppm in 22% of daily used cosmetics following SPME coupled with GC and GC-MS. Conventional solvent extraction takes around 1 h for extraction and reconcentration but SPME takes only around 10 min. SPME provides better analyses of 1,4-dioxane in nonionic surfactants and cosmetics than conventional solvent extraction and head space pretreatments in term of simplicity, speed, precision, detection limit, and solvent consumption.

Calibration↗

PubMed2005

Multiple solid-phase microextraction in a non-equilibrium situation. Application in quantitative analysis of chlorophenols and chloroanisoles related to cork taint in wine.

Multiple HS-solid-phase microextraction (MHS-SPME) is a modification of SPME developed for quantitative analysis that avoids possible matrix effects based on an exhaustive analyte extraction from the sample. In this paper, the theory of this process associated with a non-equilibrium situation has been presented. The application of an optimised HS-SPME-based method in the analysis of chloroanisoles and chlorophenols, previously acetylated, associated with the occurrence of cork taint in different red, white and rosé wine samples, has revealed the existence of matrix effects. This fact determines the choice of standard addition as the adequate technique for the quantification of these compounds in real samples. MHS-SPME is proposed as a good alternative technique with respect to HS-SPME because it avoids matrix effects, simplifies the quantification of these compounds in real samples and reduces analysis time, providing sensitivity below chloroanisole sensory threshold with acceptable precision.

Anisoles↗

PubMed2006

Application of a static solid-phase microextraction procedure combined with liquid-liquid extraction to determine poly(dimethyl)siloxane-water partition coefficients for selected polychlorinated biphenyls.

A static solid-phase microextraction (SPME) procedure combined with liquid-liquid extraction (LLE) was used to determine the poly(dimethyl)siloxane (PDMS)-water partition coefficients (K(f)) for selected polychlorinated biphenyl congeners (PCBs), including PCB 1, 15, 28, 47, 101, 153, 180, 202, 206, and 209. The accuracy for the measurements of analyte concentrations in the aqueous phase was ensured with a one-to-one recovery correction strategy employing one 13C-labeled PCB congener as a surrogate standard for each unlabeled PCB counterpart. The effects of coating thickness (7, 30, and 100 microm) and sample volume (130 mL and 2 L) on the K(f) values were examined experimentally and confirmed with paired t-tests. Significant dependence of K(f) values on coating thickness was found for a few heavily chlorinated congeners only, and was tentatively attributed to the use of the inaccurate effective coating volumes and the structural variation with these PDMS coatings. In addition, no significant differences in the log K(f) values of all analytes except for PCB 206 were found between the sample sizes of 130 mL and 2 L for both the 7- and 100-microm coatings. Overall, K(f) values obtained with 2-L sample containers were consistently higher than those reported in the literature, which is attributable to the selection of appropriate equilibrium times for SPME and direct measurements of aqueous analyte concentrations with LLE in the present study.

Dimethylpolysiloxanes↗

PubMed2000

Determination of polycyclic aromatic hydrocarbons in waste water by off-line coupling of solid-phase microextraction with column liquid chromatography.

A new method for the determination of polycyclic aromatic hydrocarbons (PAHs) in waste water using solvent-free solid-phase microextraction (SPME) is described. The PAHs are extracted with a 100 microm polydimethylsiloxane (PDMS) fiber, desorbed in 40 microl acetonitrile and measured with LC and fluorescence detection. The detection limits of this very simple method under the given conditions (extraction from 5 ml sample, extraction time 1 h) are in the range of 1-6 ng l(-1). The standard deviations (n = 6) at a concentration level of 0.8 microg l(-1) are between 1.8 and 14.4%. The procedure was used for the determination of PAHs in contaminated water samples.

Chromatography, Liquid↗

PubMed2002

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

A method for the determination of trace amounts of the herbicide oxadiazon was developed using headspace solid-phase microextraction (HS-SPME), gas chromatography-mass spectrometry (GC-MS) and selected ion monitoring. It was applied to determine oxadiazon in ground water, agricultural soil, must, wine and human urine samples. To determine oxadiazon in liquid samples, a response surface methodology generated with a Doehlert design was applied to optimize the HS-SPME conditions using a 100 microm polydimethylsiloxane fibre. For the analysis of soil samples, they were mixed with water and the SPME fibre suspended in the headspace above the slurry. Ground water, human urine and must show linear concentration range of application of 0.5-50 ng ml(-1)' with detection limits < or =0.02 ng ml(-1). HS-SPME-GC-MS analysis yielded good reproducibility (RSD values between 6.5 and 13.5%). The method validation was completed with spiked matrix samples. The developed analytical procedure is solvent free, cost effective and fast.

Gas Chromatography-Mass Spectrometry↗

PubMed2003

Headspace solid-phase microextraction in combination with gas chromatography-mass spectrometry for the rapid screening of organophosphorus insecticide residues in strawberries and cherries.

A headspace solid-phase microextraction (HS-SPME) method in combination with GC-MS was used for the extraction and quantification of diazinon, fenitrothion, fenthion, parathion ethyl, bromophos methyl, bromophos ethyl and ethion. The method was developed using a 100-microm poly(dimethylsiloxane) fiber. The obtained results showed higher responses of the insecticides after addition of aliquots of water and solvent to the fruit samples. Calibration curves that were constructed for the analytes spiked into strawberry and cherry samples followed linear relationships with good correlation coefficients (R2 > 0.986). Linearity range was between 50 and 500 microg/kg and the precision was found to be lower than 15% when applying the optimized HS-SPME procedure to fruit samples. Limits of detection in both strawberry and cherry samples using GC-MS (selected ion monitoring mode) were below 13 microg/kg. Moreover, the HS-SPME method was applied to the analysis of fruit samples and compared with liquid-liquid extraction. Results obtained in this study were in good agreement with those obtained using liquid-liquid extraction demonstrating that the recommended procedure was a fast, accurate and stable sample pretreatment method obtaining good efficiency for the extraction of organophosporus insecticides from strawberries and cherries.

Fragaria↗

PubMed2003

Use of solid-phase microextraction coupled with gas chromatography for the determination of residual solvents in pharmaceutical products.

The aim of this work was to prove that solid-phase microextraction coupled with gas chromatography could be used for the determination and quantification of residual solvents in drugs. Four solvents were selected for the experiments: ethanol, cyclohexane, triethylamine and pyridine, together with a model powdered drug substance. Several kinds of fibers, together with the extraction mode, were evaluated to determine the most appropriate one for the simultaneous extraction of the four solvents. The most promising conditions were obtained with the Carboxen-polydimethylsiloxane fiber in the headspace of the aqueous solution that contained the dissolved powder. A concentrated phosphate buffer was added to the aqueous solution to set the pH at 9.6 in order to enable good extraction of triethylamine, and the optimum extraction time was experimentally determined. A multi-criteria optimization was also carried out by means of design of experiments to optimize remaining parameters: the extraction temperature was set at 40 degrees C, the ionic strength at 1.77 mol (l-1) and the volume of the aqueous solution at 7.2 ml. The method of standard additions was used for quantitative analysis. Its performance was evaluated and validated: the pooled RSD was around 15%, the limits of detection were all of the ppb level and the method was both accurate and linear.

Chromatography, Gas↗

PubMed2003

Qualitative and quantitative solid-phase microextraction gas chromatographic-mass spectrometric determination of the low-molecular-mass compounds released from poly(vinyl chloride)/polycaprolactone-polycarbonate during ageing.

A solid-phase microextraction (SPME) method was developed to quantitatively determine the amount of 6-hydroxyhexanoic acid in aqueous solutions. The SPME method in combination with GC-MS was then applied to identify and quantify the low-molecular-mass compounds migrating from a new poly(vinyl chloride) (PVC) material, PVC/polycaprolactone-polycarbonate (PCL-PC) during ageing in water. It was shown that only a small amount of 6-hydroxyhexanoic acid, the final hydrolysis product of PCL-PC, migrated from the blend during ageing at 37 and 70 degrees C. If, however, the temperature was raised to 100 degrees C rapid hydrolysis of PCL-PC resulted. In addition to 6-hydroxyhexanoic acid, 6-hydroxyhexanoic acid dimer, caprolactone, different carboxylic acids, acetophenone and phenol were identified. SPME-GC-MS was also applied to monitor the low-molecular-mass compounds migrating from the PVC/PCL-PC blend during thermo-oxidation.

Calibration↗

PubMed2003

Application of polyphenylmethylsiloxane coated fiber for solid-phase microextraction combined with microwave-assisted extraction for the determination of organochlorine pesticides in Chinese teas.

Polyphenylmethylsiloxane (PPMS) as a novel coating for solid-phase microextraction (SPME) combined with microwave-assisted extraction (MAE) has been applied to determine the concentrations of organochlorine pesticides (OCPs) in Chinese teas. The characteristics of PPMS fiber, the extraction modes of SPME, the extraction time, temperature, and salt effects were investigated. Microwave irradiation time and power were also studied. Compared with commercial polydimethylsiloxane (PDMS) fiber and homemade sol-gel polymethylsiloxane (PMS) fiber, the novel porous sol-gel PPMS fiber exhibited high sensitivity and selectivity for OCPs compounds, higher thermal stability (to 350 degrees C) and long service life (more than 150 times). The recoveries of MAE is compared with that of ultrasonic extraction (USE), MAE-SPME-gas chromatography (GC)/electron-capture detection (ECD) methods showed better results for Chinese teas. Linear ranges of OCPs in the blank green tea was 0.1-10(3) ng/l. Detection limits of this method are below 0.081 ng/l. Recoveries of this method are between 39.05 and 94.35%. The repeatability of the technique was less than 16% relative standard deviation (R.S.D.). The tested pesticides in three Chinese teas were at the ng/g level.

Chromatography, Gas↗

PubMed1998

Headspace solid-phase microextraction for the determination of volatile and semi-volatile pollutants in water and air.

In this work we report the use of solid-phase microextraction (SPME) to extract and concentrate water-soluble volatile as well as semi-volatile pollutants. Both methods of exposing the SPME fibre were utilised: immersion in the aqueous solution (SPME) and in the headspace over the solution (HSSPME). The proposed HSSPME procedure was compared to conventional static headspace (HS) analysis for artificially spiked water as well as real water samples, which had been, equilibrated with various oil and petroleum products. Both techniques gave similar results but HSSPME was much more sensitive and exhibited better precision. Detection limits were found to be in the sub-ng/ml level, with precision better than 5% R.S.D. in most cases. To evaluate the suitability of SPME for relatively high contamination level analysis, the proposed HSSPME method was applied to the screening of run-off water samples that had heavy oil suspended in them from a tire fire incident. HSSPME results were compared with liquid--liquid extraction. Library searches were conducted on the resulting GC-MS total ion chromatograms to determine the types of compounds found in such samples. Both techniques found similar composition in the water samples with the exception of alkylnaphthalenes that were detected only by HSSPME. A brief study was carried out to assess using SPME for air monitoring. By sampling and concentrating the volatile organic compounds in the coating of the SPME fibre without any other equipment, this new technique is useful as an alternative to active air monitoring by means of sampling pumps and sorbent tubes.

Air Pollutants↗