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Solid-phase Microextraction (solid-phase + microextraction)
Kinds of Solid-phase Microextraction Selected AbstractsAnalysis of Volatile Compounds in Beef Fat by Dynamic-Headspace Solid-Phase Microextraction Combined with Gas Chromatography,Mass SpectrometryJOURNAL OF FOOD SCIENCE, Issue 5 2008A. Watanabe ABSTRACT:, A solid-phase microextraction (SPME) technique has been applied to the determination of the volatile compounds, including diterpenoids and lactones, in cooked beef fat. The ability of static-headspace SPME to extract lactones was disappointing, regardless of the type of SPME fiber or the temperature used. Dynamic-headspace SPME extraction with 50-/30-,m divinylbenzene-Carboxen on a polydimethylsiloxane fiber at 100 °C, by contrast, enabled the analysis of volatiles, including delta-lactones, gamma-lactones, and diterpenoids, with 50-/30-,m divinylbenzene-Carboxen on a polydimethylsiloxane fiber at 100 °C. Fifty-three compounds were identified from only 0.20 g of rendered beef fat, and 76% of these showed reliable peak size repeatability: the coefficient of variation was less than 10% on the total ion chromatograms obtained from gas chromatography,mass spectrometry (GC,MS) analysis. Some lactones showed higher CV values (>10%), but single-ion mode GC,MS analysis reduced them to 10% or less. In a study of beef samples available to the Japanese market, our analytical procedure revealed significantly higher levels of 1-hexanol, octadecane, ethyl tetradecanoate, gamma-nonalactone, but lower levels of delta-decalactone, delta-dodecalactone, and neophytadiene, in Japanese Black cattle than in beef imported from Australia. [source] Screening of Volatile Composition of Lavandula hybridaReverchon II Honey Using Headspace Solid-Phase Microextraction and Ultrasonic Solvent ExtractionCHEMISTRY & BIODIVERSITY, Issue 3 2009Igor Jerkovi Abstract The volatiles of unifloral Lavandula hybridaReverchon II honey were isolated by means of headspace solid-phase microextraction (HS-SPME) and ultrasonic solvent extraction (USE) and analyzed by gas chromatography and mass spectrometry (GC, GC/MS). A total of 23 compounds were identified in the headspace with hexan-1-ol, hexanal, acetic acid, hotrienol, and 2-phenylacetaldehyde as the principal components. Three solvents of different polarity were used for USE, and a total of 53 compounds were identified. The extracts with pentane/Et2O 1,:,2 (v/v) were the most representative for USE method containing the majority of the honey floral origin compounds and potential biomarkers (hexanol, acetic acid, butane-1,3-diol, butane-2,3-diol, benzoic acid, coumarin, and 2-phenylacetic acid). The total number of identified compounds (USE and HS-SPME) was 59. In general, the comparison with volatiles of other lavandin honeys of different geographic origins indicated several similarities, while acetic and formic acids were identified with high percentages in L. hybridaReverchon II honey. [source] Inhibition of aquatic toxicity of pyrethroid insecticides by suspended sedimentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2006Weichun Yang Abstract The use of pyrethroid insecticides is increasing in both agricultural and urban environments. Although pyrethroids display very high acute toxicities to water column organisms in laboratory tests, environmental water samples typically contain suspended sediment (SS) that can reduce the freely dissolved concentration of pyrethroids, hence their bioavailability. Consequently, phase distribution could play an important role in pyrethroid aquatic toxicology. In this study, we evaluated the effect of SS on the acute toxicity of four widely used pyrethroid insecticides to Ceriodaphnia dubia. In all assays, median lethal concentrations (LC50s) consistently increased with increasing SS, demonstrating the pronounced inhibitory effects of SS on pyrethroid toxicity. The LC50s in the 200 mg/L SS solutions were 2.5 to 13 times greater than those measured in sediment-free controls. Solid-phase microextraction (SPME) was used to determine the apparent distribution coefficient Kd for the pyrethroids in the water samples. Under the assumption that only the freely dissolved fraction is bioavailable, the measured Kd was used to predict C. dubia LC50s in the water samples. The predicted LC50s were within a factor of two of the measured values for 95% of the treatments. Results from this study suggest that the inhibitory effect of SS can be highly significant and must be considered in estimating exposures to pyrethroids in aquatic systems. The SPME methodology could be used effectively to measure bioavailable concentration and to predict the actual ecotoxicologic effects of pyrethroids. [source] Analysis of tricyclic antidepressant drugs in plasma by means of solid-phase microextraction-liquid chromatography-mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2007Claudete Alves Abstract Solid-phase microextraction coupled to liquid chromatography and mass spectrometry (SPME-LC-MS) was used to analyze tricyclic antidepressant drugs desipramine, imipramine, nortriptyline, amitriptyline, and clomipramine (internal standard) in plasma samples. SPME was performed by direct extraction on a PDMS/DVB (60 µm) coated fiber, employing a stirring rate of 1200 rpm for 30 min, pH 11.0, and temperature of 30 °C. Drug desorption was carried out by exposing the fiber to the liquid chromatography mobile phase for 20 min, using a labmade SPME-LC interface at 50 °C. The main variables experimentally influencing LC-MS response were evaluated and mathematically modeled. A rational optimization with fewer experiments was achieved using a factorial design approach. The constructed empirical models were adjusted with 96,98% of explained deviation allowing an adequate data set comprehension. The chromatographic separation was realized using an RP-18 column (150 mm × 2.1 mm, 5 µm particles) and ammonium acetate buffer (0.01 mol/l, pH 5.50) : acetonitrile (50 : 50 v/v) as mobile phase. Low detection levels were achieved with electrospray interface (0.1 ng/ml). The developed method showed specificity, linearity, precision, and limit of quantification adequate to assay tricyclic antidepressant drugs in plasma. Copyright © 2007 John Wiley & Sons, Ltd. [source] Solid-phase microextraction for the determination of benzoylureas in orange juice using liquid chromatography combined with post-column photochemically induced fluorimetry derivatization and fluorescence detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2008Piedad Parrilla Vázquez Abstract A solid-phase microextraction (SPME) method has been developed for the determination of six benzoylureas (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, lufenuron, and flufenoxuron) in natural orange juice based on the direct immersion mode of a 60 ,m polydimethylsiloxane/divinylbenzene fiber. An orange juice was obtained from blended, homogenized, and diluted ecological natural orange juice samples. An aliquot of 3 mL of a spiked sample was extracted under optimum SPME conditions. The determination of benzoylureas was carried out using HPLC combined with post-column photochemically induced fluorimetry derivatization and fluorescence detection. The limits of quantification obtained in matrix were within the range of 0.02 to 0.04 mg/kg and these limits are lower than the maximum residue levels established in Spanish regulations for all pesticides in this study. Recoveries in juice samples ranged between 85 and 110% and relative standard deviations between 1.8 and 7.4%. [source] Optimization of solid-phase microextraction methods for GC-MS determination of terpenes in wineJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2005Rosa M Peña Abstract Solid-phase microextraction using a 100 µm poly(dimethylsiloxane) fiber, followed by gas chromatography,mass spectrometry determination, has been optimized for the analysis of some terpenes in wine samples. The best results were obtained by direct immersion of the fiber using a sampling period of 15 min with constant magnetic stirring (1100 rpm) and an extraction temperature of 20 °C. The sample volume was 7 ml with 25% NaCl, in a 15 ml capped vial. Desorption was performed directly in the gas chromatograph injector port over 5 min at 250 °C using the splitless mode. The method is sensitive, with detection limits between 11 and 25 µg l,1, precise, with variation coefficients in the range 1.28,3.71%, and linear over more than one order of magnitude. The related conditions were used for wine sample analyses with recoveries between 71.8 and 90.9%. Solid-phase microextraction remains an attractive alternative technique due to its rapidity and because it is a solvent-free extraction. Copyright © 2005 Society of Chemical Industry [source] Potential mechanism for detection by Apis mellifera of the parasitic mite Varroa destructor inside sealed brood cellsPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2002Caroline Martin Abstract The parasitic mite Varroa destructor Anderson & Trueman is a major pest of the honeybee Apis mellifera L. throughout the world. Chemical agents currently used for mite control leave contaminating residues and promote pesticide resistance. As an alternative means of control, it would be useful to identify natural substances enabling bees to detect Varroa inside brood cells. These substances could then be used to trigger mite hygienic behaviour by bees. In this study several techniques were used to screen substances that might allow detection of infested brood cells by bees. Gas chromatography-mass spectrometry analysis was performed on substances extracted in dichloromethane from the contents of brood cells. Solid phase microextraction and solid injection were performed on substances obtained from living and dead Varroa, respectively. Electroantennography was performed to assess the sensitivity of olfactory receptors in bee antennae to some of these substances. Principal component analysis based on proportions of cuticular substances allowed discrimination between bees and other cell contents. Foundress Varroa exhibited the greatest dissimilarity to healthy pupae that were used as controls. Immature Varroa and faecal material were intermediate. High molecular weight compounds, mainly dimethylalkanes, were proportionally the most characteristic components of foundress Varroa. This finding suggests that these compounds would be the most apt to induce uncapping of cells infested by Varroa. Solid-phase microextraction and solid injection demonstrated the presence of aliphatic acids, esters, and one alcohol, eicosenol, in Varroa. Electroantennographic recordings showed that mite-resistant bees were more responsive to some acids and one ester. We speculate that these compounds may be involved in recognition of living Varroa by honeybees. [source] Solid-phase microextraction combined with surface-enhanced laser desorption/ionization introduction for ion mobility spectrometry and mass spectrometry using polypyrrole coatingsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2004Yan Wang The successful application of polypyrrole (PPY) solid-phase microextraction (SPME) coatings as both an extraction phase and a surface to enhance laser desorption/ionization (SELDI) of analytes is reported. This SPME/SELDI fiber integrates sample preparation and sample introduction on the tip of a coated optical fiber, as well as acting as the transmission medium for the UV laser light. Using ion mobility spectrometry (IMS) detection, the signal intensity was examined as a function of extraction surface area and concentration of analyte. The linear relationship between concentration and signal intensity shows potential applicability of this detection method for quantitative analysis. Extraction time profiles for the fiber, using tetraoctylammonium bromide as test analyte, illustrated that equilibrium can be reached in less than one minute. To investigate the performance of the PPY coating, the laser desorption profile was studied. The fiber was also tested using a quadrupole time-of-flight (Q-TOF) mass spectrometer with leucine enkephalin as test analyte. Since no matrix was used, mass spectra free from matrix background were obtained. This novel SPME/SELDI fiber is easy to manufacture, and is suitable for studying low-mass analytes because of the intrinsic low background. These findings suggest that other types of conductive polymers could also be used as an extraction phase and surface to enhance laser desorption/ionization in mass spectrometry. Copyright © 2003 John Wiley & Sons, Ltd. [source] Coupling of solid-phase microextraction continuous bed (monolithic) capillaries with capillary zone electrophoresis for direct analysis of drugs in biological fluids,ELECTROPHORESIS, Issue 8 2008Reda Jarmalavi Abstract Hyperlink robust biocompatible solid-phase microextraction (SPME) devices were prepared using continuous bed (monolithic) restricted-access media (RAM) as the SPME capillary insert. The RAM-based SPME approach was able to simultaneously separate proteins from a biological sample, while directly extracting the active components of caffeine, paracetamol and acetylsalicylic acid from the drug NeoCitramonum. The devices were interfaced with a CZE system and fully automated analysis for sample preconcentration, desorption, separation and quantification of analytes was evaluated. Comparative study of in-line coupled SPME,CZE using RAM and RP capillary inserts was carried out. Using an SPME (RAM) insert, the calculated caffeine, paracetamol and acetylsalicylic acid LODs in a bovine plasma sample were 0.3, 0.8 and 1.9,ng/mL, respectively. [source] Poly(methacrylic acid-ethylene glycol dimethacrylate) monolith in-tube solid-phase microextraction applied to simultaneous analysis of some amphetamine derivatives in urine by capillary zone electrophoresisELECTROPHORESIS, Issue 16 2005Fang Wei Abstract A method based on in-tube solid-phase microextraction and capillary zone electrophoresis (CZE) was proposed for simultaneously determining four amphetamines (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine) in urine. A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column, which can provide sufficient extraction efficiency, was introduced for the extraction of amphetamines from urine samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the samples were analyzed by CZE. The best separation was achieved using a buffer composed of 0.1,M disodium hydrogen phosphate (adjusted to pH,4.5 with 1,M hydrochloric acid) and 20% methanol v/v, with a temperature and voltage of 25°C and 20,kV, respectively. By applying electrokinetic injection with field-amplified sample stacking, detection limits of 25,34,µg/L were achieved. Excellent method of reproducibility was found over a linear range of 0.1,5,mg/L. Determination of these analytes from abusers' urine sample was also demonstrated. [source] Influence of soil type and organic matter content on the bioavailability, accumulation, and toxicity of ,-cypermethrin in the springtail Folsomia candidaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2010Bjarne Styrishave Abstract The influence of organic matter (OM) content on ,-cypermethrin porewater concentrations and springtail Folsomia candida accumulation was investigated in two soils with different levels of organic matter, a forest soil with a total organic carbon (TOC) content of 5.0% (OM,=,11.5%) and an agricultural soil with a TOC content of 1.3% (OM,=,4.0%). Also, the effects of ,-cypermethrin concentrations in soil and pore water and the influence of soil aging on springtail reproduction were investigated. Springtail reproduction was severely affected by increasing ,-cypermethrin in soil with 1.3% TOC; the median effective concentration value (EC50) was estimated to 23.4,mg/kg (dry wt). Reproduction was only marginally affected in the soil with 5.0% TOC, and no EC50 value could be estimated. However, when expressing ,-cypermethrin accumulation as a function of soil ,-cypermethrin concentrations, no difference was found between the two soil types, and no additional ,-cypermethrin uptake was observed at soil concentrations above approximately 200,mg/kg (dry wt). By using solid-phase microextraction (SPME), it could be demonstrated that ,-cypermethrin porewater concentrations were higher in the soil with low organic matter (LOM) content than in the soil with high organic matter (HOM) content. Furthermore, a clear relationship was found between ,-cypermethrin concentrations in springtails and porewater. Soil aging was not found to exert any effect on ,-cypermethrin toxicity toward springtails. The study indicates that the springtail's accumulation of ,-cypermethrin and reproduction is governed by ,-cypermethrin porewater concentrations rather than the total ,-cypermethrin concentration in soil. Environ. Toxicol. Chem. 2010;29:1084,1090. © 2010 SETAC [source] Phase distribution of synthetic pyrethroids in runoff and stream waterENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Weiping Liu Abstract Synthetic pyrethroids (SPs) are a group of hydrophobic compounds with significant aquatic toxicity. Their strong affinity to suspended solids and humic materials suggests that SPs in natural surface water are distributed in solid-adsorbed, dissolved organic matter (DOM)-adsorbed, and freely dissolved phases. The freely dissolved phase is of particular importance because of its mobility and bioavailability. In the present study, we used solid-phase microextraction to detect the freely dissolved phase, and we evaluated the phase distribution of bifenthrin and permethrin in stream and runoff waters. In stream water, most SPs were associated with the suspended solids and, to a lesser extent, with DOM. The freely dissolved phase contributed only 0.4% to 1.0%. In runoff effluents, the freely dissolved concentration was 10% to 27% of the overall concentration. The predominant partitioning into the adsorbed phases implies that the toxicity of SPs in surface water is reduced because of decreased bioavailability. This also suggests that monitoring protocols that do not selectively define the freely dissolved phase can lead to significant overestimation of toxicity or water-quality impacts by SPs. [source] Validation of a modified Flory-Huggins concept for description of hydrophobic organic compound sorption on dissolved humic substancesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2002Anett Georgi Abstract Sorption coefficients(KDOC) on dissolved organic matter (DOM) have been determined by means of solid-phase microextraction (SPME) for hydrophobic organic compounds (HOCs) of various classes, for example, polycyclic aromatic hydrocarbons (PAHs), noncondensed arenes, and alkanes. Relating the KDOC values obtained to the octanol-water partition coefficients of the solutes results in class-specific correlations. Obviously, PAHs have a higher affinity to DOM than other HOCs with equal KOW values. The different KDOC to KOW correlations can be combined into one general formula based on a modified Flory-Huggins concept. It permits the calculation of sorption coefficients from the solubility parameters (,) and KOW values of the solutes and the solubility parameter of the sorbent. The latter value, which is specific to the DOM under consideration, can be determined from a single measured sorption coefficient. By applying the proposed Flory-Huggins concept, which is based on the presumption of nonspecific interactions between HOCs and DOM, the different affinities of PAHs, noncondensed arenes, and alkanes to DOM can be accurately predicted. [source] Biomimetic solid-phase microextraction to predict body residues and toxicity of chemicals that act by narcosisENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2002Heather A. Leslie Abstract A biomimetic extraction technique using solid-phase microextraction (SPME) fibers has been developed for the risk assessment of contaminants with a narcotic mode of action. Our goal is to apply this technique in the future for the prediction of total baseline toxicity of environmental water and effluent samples. Validation of this method requires establishing the relationship between contaminant accumulation and toxicity in biota and accumulation in the surrogate solid phase (the SPME fiber coating). For this purpose, we determined the median lethal concentration (LC50) values for Chironomus riparius midge larvae exposed to two halogenated aromatic compounds separately and measured body residues in the exposed larvae. Solid-phase microextraction fibers with an 85-,m polyacrylate (PA) coating served as the surrogate hydrophobic phase, mimicking the uptake of the compounds by midge larvae. The toxicant concentrations in SPME fibers measured directly by gas chromatography/mass spectrometry (GCMS) or calculated from the SPME fiber,water partition coefficient, KSPME, were related to the toxicant concentrations found in midge larvae. Our results demonstrated that the biomimetic SPME method enables the estimation of body residues in biota and prediction of the degree of baseline toxicity of a water medium. [source] Measurement of Henry's law constant for methyl tert -butyl ether using solid-phase microextractionENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2001Britta G. Bierwagen Abstract Increasing groundwater contamination with methyl tert -butyl ether (MTBE) requires more efficient remediation technologies. Accurate measurement of MTBE's air,water partitioning coefficient (Henry's law constant, H) is important for the design and optimization of removal efficiency for many treatment systems as well as for predicting its fate and transport. Previously published data for MTBE appear to have some unusual nonlinearity at lower temperatures (15,30°C), and a wide range of values exists for dimensionless H at 25°C, from 0.0216 to 0.1226 in the published literature. We measured H for MTBE using headspace solid-phase microextraction (SPME) and a static method that considers equilibrium partitioning in a closed system, for temperatures between 15 and 40°C. To validate our methods, we measured H for benzene, toluene, and trichloroethylene and compared our results to previously published values, with excellent agreement. The Arrhenius plot for MTBE indicates that ln(HMBTE) = 6.85,2,900 T,1, with T in K. At 25°C, HMBTE = 0.0555 ± 0.0122. [source] Use of a bench-top photochemical reactor and solid-phase microextraction to measure semivolatile organic compound-hydroxyl radical rate constantsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2000Mary Jo Bernhard Abstract It is increasingly important to be able to measure semivolatile organic compound-hydroxyl (SOC-OH) radical rate constants and estimate semivolatile organic compounds' (SOCs) atmospheric half-lives because of potential for atmospheric long-range transport. We have used a bench-top photochemical reactor, along with solid-phase microextraction (SPME) and ethyl nitrite, to successfully measure the rate constants of naphthalene, linalool, biphenyl, and phenanthrene with hydroxyl (OH) radical. Biphenyl and phenanthrene underwent wall loss in the reactor. The wall loss rates were determined and were used to correct the measured gas-phase rate constants. The reaction rate constants for naphthalene, linalool, biphenyl, and phenanthrene with OH radical, in our bench-top system at 295 ± 3 K, were determined to be 2.73 ± 0.37 × 10,11, 1.93 ± 0.24 × 10,10, 7.44 ± 1.9 × 10,12, 1.73 ± 0.21 × 10,11 (cm3/molecule/s), respectively, and were in excellent agreement with previous studies and model predictions. Based on the range of experimental and predicted rate constants for these reactants and an estimated average OH concentration in the atmosphere, the atmospheric half-lives of these SOCs are significantly less than 2 d. This indicates that the global presence of these compounds in the atmosphere is primarily due to regional sources and not to atmospheric long-range transport. This study shows that bench-top reactors, combined with corrections for reactant wall loss and simplified analytical tools (such as solid-phase microextraction), can be used to measure SOC-OH rate constants. [source] Characterization of volatile compounds and triacylglycerol profiles of nut oils using SPME-GC-MS and MALDI-TOF-MSEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 2 2009Stefanie Bail Abstract Several nut oil varieties mainly used as culinary and overall healthy food ingredients were subject of the present study. Headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was employed in order to determine the qualitative composition of volatile compounds. Furthermore, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used in order to assess the profiles and relative composition of the prevalent triacylglycerols (TAG) within the oils. The headspace of the majority of oil samples was dominated by high contents of acetic acid (up to 42%) and hexanal (up to 32%). As nut oils are typically gained by cold-pressing from previously roasted nuts, characteristic pyrazine derivatives as well as degradation products of long-chain fatty acids were detected. TAG analysis of these oils revealed a quite homogeneous composition dominated by components of the C52 and C54 group composed mainly of oleic (18:1), linoleic (18:2), stearic (18:0) and palmitic (16:0) acid residues representing together between 65 and 95% of the investigated nut oils. The TAG profiles showed characteristic patterns which can be used as ,fingerprints' of the genuine oils. Nut oils exhibiting quite similar fatty acid composition (e.g. hazelnut, pistachio and beech oil) could be clearly discriminated based on TAG showing significant differences between the oils. [source] Variation in 4-mercapto-4-methyl-pentan-2-one release by Saccharomyces cerevisiae commercial wine strainsFEMS MICROBIOLOGY LETTERS, Issue 2 2004Kate S. Howell Abstract The volatile thiol 4-mercapto-4-methylpentan-2-one (4MMP) is a potent contributor to wine aroma. In grape juice, 4MMP is bound to cysteine as a non-volatile compound and requires the action of yeast during fermentation to release the aroma active thiol. A method was developed to measure 4MMP release from the precursor by headspace solid-phase microextraction and separation by gas chromatography with atomic emission detection to screen the ability of wine yeast to release 4MMP. Yeast commonly used in white wine making were grown with the precursor at two different temperatures, and the amount of 4MMP released was measured. The results demonstrate that yeast strain selection and fermentation temperature can provide an important tool to enhance or modulate the grape-derived aromas formed during wine fermentation. [source] Constituents of top fragrance from fresh flowers of Robinia Pseudoacacia L. occurring in ChinaFLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2006Jianchun Xie Abstract Volatiles from the fresh flowers of Robinia Pseudoacacia L. grown in China were analyzed by GC-MS combined with solid-phase microextraction (SPME). The abundant compounds identified were linalool (33.1%), cis - , -ocimene (26.6%), (E)- , -bergamotene (8.9%) and formanilide (7.4%). Copyright © 2006 John Wiley & Sons, Ltd. [source] Determination of thiol compounds by automated headspace solid-phase microextraction with in-fiber derivatizationFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2006Qing Wang Abstract In this article, headspace solid-phase microextraction (HS-SPME) analysis of thiol compounds with both solid and aqueous samples was investigated using N -phenylmaleimide as an in-fiber derivatization reagent. The derivatives were analyzed using GC-MS. The HS-SPME method was executed on an automatic sampler and optimized by studying a variety of factors such as the selection of the fiber, extraction time, temperature, agitation speed, etc. Method validation was carried out by spiking known amounts of thiol compounds into the sample and calculating the concentration by standard addition. The relative standard deviations (RSD) for the majority of the thiols were less than 10%. The developed method resulted in a limit of detection (LOD) in the low microgram per liter for most of the thiols analyzed, which was about one order of magnitude lower than the HS-SPME without derivatization. Finally, the overall method was successfully applied for the determination of thiols in yellow onion, green onion and garlic. Copyright © 2006 John Wiley & Sons, Ltd. [source] Volatile constituents of benzoin gums: Siam and Sumatra.FLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2003Part Abstract The volatile extract composition of two different benzoin gums, Siam and Sumatra, were analysed by GC,MS. Twenty components representing more than 99.1% of the oil from Siam and 29 components representing more than 97.4% of the oil from Sumatra were analysed. The major components were benzyl benzoate (76.1,80.1%) for the two oils and benzoic acid (12.5%), methyl benzoate (1.5%) and allyl benzoate (1.5%) for Siam, and styrene (2.3%), cinnamic acid (3.5%) and benzyl cinnamate (3.3%) for Sumatra. Volatile compounds of oils and crushed benzoins were also studied using solid-phase microextraction (SPME) employing carboxen/polydimethylsiloxane and carbowax/divinylbenzene ,bres. Copyright © 2003 John Wiley & Sons, Ltd. [source] Aroma profile of Niagara grape juice contaminated with multicoloured Asian lady beetle taint using gas chromatography/mass spectrometry/olfactometryINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2010Carolyn F. Ross Summary The objective of this study was to determine the odour-active compounds present in Niagara grape juice tainted with multicoloured Asian lady beetle (MALB: Harmonia axyridis: Coleoptera: coccinellidae). Niagara grape juice was made with (2.5 MALB/L) and without MALB and evaluated using solid-phase microextraction coupled with gas chromatography/mass spectrometry/olfactometry (GC/MS/O) to tentatively identify compounds. Compared to the control juice, phenol, described as musty/mouldy, was found to be unique to the MALB-tainted grape juice. The four odourants significantly higher in the MALB-tainted grape juice were described as fruity, asparagus, stagnant water/chemical and musty/mouldy, tentatively corresponding to octanal, 3-sec-butyl-2-methoxypyrazine (SBMP), 2-methoxy-4-methylphenol and decanal, respectively. Three of the five compounds found in the MALB-tainted juice have been reported to be produced by live MALB. While past literature has focused on the contribution of 3-alkyl-2-methoxypyrazines to MALB-taint, the present study suggests other compounds, in addition to SBMP, may contribute to the aroma profile of MALB-tainted grape juice. [source] Onion aphid (Neotoxoptera formosana) attractants, in the headspace of Allium fistulosum and A. tuberosum leavesJOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2007M. Hori Abstract:, Attractancy of Allium fistulosum L. and Allium tuberosum Rottl. to adult apterae of the onion aphid, Neotoxoptera formosana (Takahashi), an oligophagous aphid pest of Allium crops, was investigated with a Y-tube olfactometer. The aphids were significantly attracted to both A. fistulosum and A. tuberosum. The headspace components of both plants were extracted with solid-phase microextraction (SPME) and analysed by gas chromatography-mass spectrometry (GC-MS). The main volatile components of A. fistulosum were dipropyl disulphide (relative contents: 67%), 1-propenyl propyl disulphide (23%) and dipropyl trisulphide (6%). In the headspace of A. tuberosum, diallyl disulphide was detected as the main component (58%). Attractancy of dipropyl disulphide, dipropyl trisulphide and diallyl disulphide to the aphids was examined with the Y-tube olfactometer. The aphids were significantly attracted to dipropyl trisulphide and diallyl disulphide at a concentration of 0.01%. Dipropyl disulphide did not significantly attract the aphids at any concentrations tested. It was revealed that attractancy of A. fistulosum and A. tuberosum was caused by dipropyl trisulphide and diallyl disulphide, respectively. The findings suggest that N. formosana uses these sulphur compounds, characteristic components of Allium plants, as olfactory cues to find the host plants. [source] PHYSICOCHEMICAL AND FLAVOR CHANGES OF FRAGRANT BANANA (MUSA ACUMINATA AAA GROUP "GROSS MICHEL") DURING RIPENINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2010SOMRUEDEE THAIPHANIT ABSTRACT The objective of this research was to characterize the physicochemical and flavor changes that occur in ripe Hom Thong (Musa acuminata AAA Group "Gross Michel") flesh at stage 6,8. It was found that the higher fresh maturity stage of Hom Thong at P < 0.05 has the following results: the antioxidant activities, moisture content and reducing sugar are significantly increased. The titratable acidity, total soluble solid and prebiotic activities' score for Lactobacillus acidophilus LA5 and Bifidobacterium lactis BB-12 are significantly decreased. The total dietary fiber remains unchanged. Using headspace solid-phase microextraction and gas chromatography,mass spectrometry to characterize volatile compound found that the flavor 20 volatile compounds (11 esters, 5 alcohols, 3 carbonyls and 1 ketone) are varied on Hom Thong maturity stage. The compounds with the most aroma impact for ripe Hom Thong flesh at stage 6,8 were 3-methylbutyl butanoate, 3-methyl-1-butyl acetate, 3-methylbutyl 3-methylbutanoate and 2-methylpropyl ethanoate. PRACTICAL APPLICATIONS Ripe banana Musa acuminata, AAA Group "Gross Michel," locally known in Thailand as Hom Thong, is a popular food item consumed as fruit, snacks or food ingredients for confections, spreads and other banana products. Using a suitable ripening stage of the banana flesh is the most critical step among many steps of unit operations for achieving high-quality banana products. This study not only characterizes the physicochemical and flavor changes that occur in ripe Hom Thong flesh at stage 6,8, but also studies antioxidant activities and prebiotic activities. Manufacturers can utilize the data presented in this article to select the suitable ripening stage in order to avoid product failure and to produce the best quality products for functional food, pharmafood, medifood or vitafood that are rich in natural banana flavor. [source] FLAVOR AND AROMA ATTRIBUTES OF RIESLING WINES PRODUCED BY FREEZE CONCENTRATION AND MICROWAVE VACUUM DEHYDRATIONJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2006C. CLARY ABSTRACT This article describes the production of sweet dessert wines produced using late-harvest freeze concentration, wine produced from fresh grapes frozen using refrigeration and wine produced from grapes partially dried using microwave vacuum dehydration. The objective was to compare the aroma and flavor attributes of the wines to determine the effect of each method of juice concentration. The replicated wine samples were evaluated by 12 experienced judges, and the wines were analyzed using solid-phase microextraction. The microextraction detected 28 compounds; however, levels of concentration of these compounds were below published aroma thresholds. Although all the wines were judged as acceptable sweet dessert wines, the judges detected significant differences. The wine made from the dehydrated grapes exhibited lower fresh fruit aroma, higher fusel oils and oxidation, and flavor notes including citrus/grapefruit and acidity were lower. [source] Analysis of Volatile Compounds in Beef Fat by Dynamic-Headspace Solid-Phase Microextraction Combined with Gas Chromatography,Mass SpectrometryJOURNAL OF FOOD SCIENCE, Issue 5 2008A. Watanabe ABSTRACT:, A solid-phase microextraction (SPME) technique has been applied to the determination of the volatile compounds, including diterpenoids and lactones, in cooked beef fat. The ability of static-headspace SPME to extract lactones was disappointing, regardless of the type of SPME fiber or the temperature used. Dynamic-headspace SPME extraction with 50-/30-,m divinylbenzene-Carboxen on a polydimethylsiloxane fiber at 100 °C, by contrast, enabled the analysis of volatiles, including delta-lactones, gamma-lactones, and diterpenoids, with 50-/30-,m divinylbenzene-Carboxen on a polydimethylsiloxane fiber at 100 °C. Fifty-three compounds were identified from only 0.20 g of rendered beef fat, and 76% of these showed reliable peak size repeatability: the coefficient of variation was less than 10% on the total ion chromatograms obtained from gas chromatography,mass spectrometry (GC,MS) analysis. Some lactones showed higher CV values (>10%), but single-ion mode GC,MS analysis reduced them to 10% or less. In a study of beef samples available to the Japanese market, our analytical procedure revealed significantly higher levels of 1-hexanol, octadecane, ethyl tetradecanoate, gamma-nonalactone, but lower levels of delta-decalactone, delta-dodecalactone, and neophytadiene, in Japanese Black cattle than in beef imported from Australia. [source] Characterization of a Cabbage Off-flavor in Whey Protein IsolateJOURNAL OF FOOD SCIENCE, Issue 2 2006Joy M. Wright ABSTRACT Whey protein isolate (WPI) is a value-added protein with multiple ingredient applications. A bland flavor is expected in WPI, and off-flavors can limit its use in foods. Recently, a cabbage off-flavor was noted in some WPI. The objective of this study was to characterize the source of cabbage flavor in WPI. WPI with and without cabbage flavor were collected, and descriptive sensory analysis was conducted on the rehydrated WPI using a trained panel and a previously identified sensory language. Volatile compounds were extracted by solvent extraction followed by solvent-assisted flavor evaporation (SAFE), followed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GCO), to identify and characterize aroma-active compounds. Dimethyl trisulfide (DMTS) (cabbage aroma) was identified by GCO and GC-MS in WPI with the cabbage flavor. DMTS was quantified by solid-phase microextraction (SPME) with GC-MS. Orthonasal thresholds of DMTS in deodorized water and WPI were determined by ascending forced choice analysis, and descriptive analysis of model systems was used to confirm instrumental results. DMTS levels were 1.94 ± 0.26 and 3.25 ± 0.61 parts per billion (ppb) in WPI with cabbage flavor, and 0.44 ± 0.25 and 0.43 ± 0.18 ppb in those without cabbage flavor. The orthonasal thresholds for DMTS in water and WPI were 0.07 ± 1.28 parts per trillion (ppt) and 0.80 ± 0.45 ppb, respectively. Descriptive analysis of model systems confirmed the role of DMTS in the cabbage off-flavor. Knowledge of the source of this flavor will aid in identification of ways to minimize or prevent DMTS formation in WPI. [source] Effect of Gamma-Irradiated Red Pepper Powder on the Chemical and Volatile Characteristics of Kakdugi, a Korean Traditional Fermented Radish KimchiJOURNAL OF FOOD SCIENCE, Issue 7 2005Jeung Hee Lee ABSTRACT The chemical and volatile characteristics of kakdugi batches prepared with irradiated red pepper powders were determined during fermentation for 7 wk at 5 °C. Acidities of kakdugies with irradiated red pepper powder (3, 5, and 7 kGy) were lower than that of kakdugi with nonirradiated control at 3 wk of fermentation, which indicated that the irradiated red pepper powder might delay the initial fermentation. Pungency and red color caused by capsanoids and capsanthin, respectively, were not altered by irradiated red pepper powder, whereas the fermentation decreased the capsanoid content. The headspace volatile compounds extracted by solid-phase microextraction, except 2-tricanone, were not significantly different in fresh made kakdugies with red pepper powder irradiated at dosed of 0, 3, 5, and 7 kGy; however, as fermentation progressed, the composition of volatiles was changed. A FOX 3000 electronic nose separated the odor of kakdugies with red pepper powder irradiated at 0, 3, 5, and 7 kGy into 4 different groups, and the odor patterns developed differently during fermentation. [source] Effect of Gamma-irradiation on Color, Pungency, and Volatiles of Korean Red Pepper PowderJOURNAL OF FOOD SCIENCE, Issue 8 2004J.H. Lee ABSTRACT: Effect of gamma-irradiation on color, pungency, and volatiles of Korean red pepper powder (Capsicum annuum L.) was investigated. Red pepper powder, vacuum-packaged in a polyethylene/polypropylene bag, was gamma-irradiated up to 7 kGy. An irradiation dose of 7 kGy reduced the population of mesophilic bacteria and fungi effectively without affecting major quality factors. Pungency of irradiated red pepper powder was not changed based on the amount of capsanoids by high-performance liquid chromatography (HPLC) and the Scoville sensory score. The red color of irradiated pepper powder was not significantly different from that of the control, judged from the capsanthin content by HPLC and color assessment using spectrophotpmetric (American Spice Trade Assn. units) and colorimetric measurements (Hunter a values). Further, the sensory evaluation showed no significant difference in pungent odor and off-odor between nonirradiated control and irradiated red pepper powder. However, when headspace volatiles of gamma-irradiated red pepper powder were evaluated by gas chromatography/ mass spectrometry with solid-phase microextraction and electronic nose with metal oxide sensors, the profiles of odor were classified into irradiated dose levels of 0, 3, 5, and 7 kGy by principal component analysis and multivariate analysis of variance. Such a difference of odor might result from the disappearance of some volatiles, such as hexanoic acid and tetramethyl-pyrazine, and the appearance of 1,3-di-tert-butylbenzene during irradiation. Moreover, it appears that the irradiation of packaging material induced a formation of 1,3-di-tertbutylbenzene, which migrated into the red pepper powder. [source] Fiber introduction mass spectrometry: determination of pesticides in herbal infusions using a novel sol,gel PDMS/PVA fiber for solid-phase microextractionJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2007Rogério Cesar da Silva Abstract An application of the direct coupling of solid-phase microextraction (SPME) with mass spectrometry (MS), a technique known as fiber introduction mass spectrometry (FIMS), is described to determine organochlorine (OCP) and organophosphorus (OPP) pesticides in herbal infusions of Passiflora L. A new fiber coated with a composite of poly(dimethylsiloxane) and poly(vinyl alcohol) (PDMS/PVA) was used. Sensitive, selective, simple and simultaneous quantification of several OCP and OPP was achieved by monitoring diagnostic fragment ions of m/z 266 (chlorothalonil), m/z 195 (,-endosulfan), m/z 278 (fenthion), m/z 263 (methyl parathion) and m/z 173 (malathion). Simple headspace SPME extraction (25 min) and fast FIMS detection (less than 40 s) of OCP and OPP from a highly complex herbal matrix provided good linearity with correlation coefficients of 0.991,0.999 for concentrations ranging from 10 to 140 ng ml,1 of each compound. Good accuracy (80 to 110%), precision (0.6,14.9%) and low limits of detection (0.3,3.9 ng ml,1) were also obtained. Even after 400 desorption cycles inside the ionization source of the mass spectrometer, no visible degradation of the novel PDMS/PVA fiber was detected, confirming its suitability for FIMS. Fast (ca 20 s) pesticide desorption occurs for the PDMS/PVA fiber owing to the small thickness of the film and its reduced water sorption. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||