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PubMed2002

Purine metabolizing capability of Enterobacter agglomerans affects volatiles production and attractiveness to Mexican fruit fly.

We investigated two strains of Enterobacter agglomerans that differ in their ability to metabolize uric acid for (1) attractiveness to sugar-fed Mexican fruit flies, and (2) production of volatile chemicals that may be responsible for the attractiveness. The two strains were cultured on a medium that contained uric acid as the primary nitrogen source to simulate bird feces, a natural substrate for this bacterium. Active cultures of both strains were more attractive than uninoculated uric acid medium to both sexes of sugar-fed flies in wind-tunnel bioassays. The uricase(+) strain was more attractive than the uricase(-) strain to males and to females <9 days old, but not to older females. Volatiles found by solid-phase microextraction in greater amounts in headspace above active cultures of both strains than above uninoculated medium were ammonia, dimethyldisulfide, 3-methylbutanol, 2-phenylethanol, 2,5-dimethylpyrazine, and trimethylpyrazine. The uricase(+) strain produced more ammonia, dimethyldisulfide, and trimethylpyrazine than the uricase(-) strain. An additional chemical, 3-hydroxybutanone, appears to be produced exclusively by the uricase(+) strain. The uricase(-) strain produced more 2-phenylethanol than the uricase(+) strain. Differences in volatiles are consistent with the generally greater attractiveness of the uricase(+) strain compared with the uricase(-) strain as ammonia, 3-hydroxybutanone, and trimethylpyrazine have been demonstrated attractive to sugar-fed Mexican fruit flies.

Animals↗

PubMed2003

Identification of host fruit volatiles from hawthorn (Crataegus spp.) attractive to hawthorn-origin Rhagoletis pomonella flies.

Solid-phase microextraction (SPME) and gas chromatography coupled with electroantennographic detection (GC-EAD) were used to identify volatile compounds from hawthorn fruit (Crataegus spp.) acting as behavioral attractants for hawthorn-infesting Rhagoletis pomonella flies. Consistent EAD activity was obtained for six chemicals: ethyl acetate (94.3%), 3-methylbutan-1-ol (4.0%), isoamyl acetate (1.5%), 4,8-dimethyl-1,3(E),7-nonatriene (0.07%), butyl hexanoate (0.01%), and dihydro-beta-ionone (0.10%). In a flight-tunnel bioassay, there was a dose-related increase in the percentage of flies flying upwind to the six-component mixture. Hawthorn-origin flies also made equivalent levels of upwind flight with the synthetic blend and an adsorbent extract of volatiles collected from whole fruit, each containing the same amount of the 3-methylbutan-1-ol compound. Significantly lower levels of upwind flight occurred to a previously identified volatile blend of ester compounds that attracts R. pomonella flies infesting domestic apples, compared with the hawthorn volatile mix. Selected subtraction assays showed further that the four-component mixture of 3-methylbutan-1-ol, 4,8-dimethyl-1,3(E),7-nonatriene, butyl hexanoate, and dihydro-beta-ionone also elicited levels of upwind flight equivalent to the six-component mix. Removal of 3-methylbutan-1-ol from the four-component blend resulted in complete loss of upwind flight behavior. Removal of dihydro-beta-ionone, 4,8-dimethyl-1,3(E),7-nonatriene, or butyl hexanoate from the four-component mixture resulted in significant decreases in the mean number of upwind flights compared to the four- or six-component mixtures.

Animals↗

PubMed2003

Residual solvent testing: a review of gas-chromatographic and alternative techniques.

The purpose of this brief review is to describe and discuss some of the current analytic procedures including gas-chromatographic and alternative techniques for residual solvent testing. Residual solvents, or organic volatile impurities, are a potential toxic risk for pharmaceutic products and have been a concern of manufacturers for many years. Residual solvents have had official limits in the United States as set in USP XXV and by the FDA in 1997 and have been monitored by most pharmaceutical manufacturers extensively for more than two decades in both bulk and finished products. The chief method of analysis for residual solvents is gas chromatography, which is generally considered the preferred methodology. Sample introduction techniques include both static and dynamic headspace analysis, solid-phase microextraction, and direct injection of solution containing bulk drug substance or drug product into the gas chromatograph. Also, some alternative methodologies for residual solvent testing are discussed in this review. In conclusion, gas chromatograph-based procedures will continue to dominate residual solvent testing because of its specificity for identification of the solvent, but the use of alternative sample introduction techniques into a gas chromatograph will continue to expand in the near future.

Chromatography, Gas↗

PubMed2003

Male bugs modulate pheromone emission in response to vibratory signals from conspecifics.

Male Nezara viridula emit a volatile sex pheromone that acts as a long-range attractant to females. Both sexes communicate through vibrations once they are on the same plant. Males respond to the female calling song by emitting a male courtship song, and they orient to the female calling song on a plant. Simultaneity between vibratory and chemical communication during the last steps of mate finding suggests that pheromone emission might be modulated by signals from conspecifics. Male volatile emissions were collected with fibers for solid-phase microextraction, while male bugs were stimulated with natural and artificial signals. Percentages of males releasing pheromone and collected amounts of pheromone increased when males were stimulated with female calling song. Pheromone emission was stable in males stimulated with male rivalry songs, and it decreased in males stimulated with a 100-Hz artificial signal. The ability of male bugs to modulate their pheromone emission may reduce metabolic costs, reduce parasitism, and offer a better synchronization of sexual activity.

Animals↗

PubMed2003

Identification of odors from overripe mango that attract vinegar flies, Drosophila melanogaster.

Bioassays with a variety of overripe fruits, including mango, plum, pear, and grape, and their extracts showed that odors from overripe mango were most attractive to adult vinegar flies, Drosophila melanogaster. Combined gas chromatography-electroantennographic detection (GC-EAD) analyses of solid-phase microextraction (SPME) and Tenax extracts of overripe mango odors showed that several volatile compounds, including ethanol, acetic acid, amyl acetate, 2-phenylethanol, and phenylethyl acetate elicited significant EAG responses from antennae of female flies. Most of the volatile compounds in the extracts were identified by mass spectral and retention index comparisons with synthetic standards. In cage bioassays, lures with a blend of ethanol, acetic acid, and 2-phenylethanol in a ratio of 1:22:5 attracted six times more flies than any single EAG-active compound. This blend also attracted four times more flies than traps baited with overripe mango or unripe mango. However, in field trials, the blend was not as attractive as suggested by the laboratory bioassay.

Animals↗

PubMed2003

A study on volatile organic compounds (VOCs) produced by tropical ascomycetous yeasts.

As a part of a program aiming at the selection of strains which might be of interest as sources of natural flavouring molecules, the production of volatile organic compounds (VOCs) by 98 ascomycetous yeast strains (representative of 40 species belonging to 12 genera) isolated from tropical environments was investigated. Volatiles produced were sampled by means of headspace solid-phase microextraction (SPME) and the compounds were analysed and identified by gas chromatography-mass spectroscopy (GC-MS). The VOCs produced were found to be alcohols (amyl alcohol and isoamyl alcohol), aldehydes (2-methyl-2-hexenal and 2-isopropyl-5-methyl-2-hexenal) and esters (ethyl isobutyrate, isobutyl acetate, isoamyl acetate, 2-methylbutyl acetate, ethyl isovalerate, isoamyl propionate and phenylmethyl acetate). Differences in VOC profiles were used to cluster the yeast strains into 25 VOC phenotypes. The different frequency of VOC phenotypes in three specific habitats was correlated to the divergent environmental conditions, possibly affecting the selection of specific yeasts. From a biotechnological viewpoint, this study reveals the potentiality of ascomycetous yeasts isolated from tropical environments as a promising source of VOCs relevant in food and fragrance industry.

Alcohols↗

PubMed2003

Identification of host fruit volatiles from flowering dogwood (Cornus florida) attractive to dogwood-origin Rhagoletis pomonella flies.

Solid-phase microextraction and gas chromatography coupled with electroantennographic detection were used to identify volatiles from fruit of flowering dogwood, Cornus florida, as key attractants for Rhagoletis pomonella flies originating from dogwood fruit. A six-component blend containing ethyl acetate (54.9%), 3-methylbutan-1-ol (27.5%), isoamyl acetate (0.9%), dimethyl trisulfide (1.9%), 1-octen-3-ol (9.1%), and beta-caryophyllene (5.8%) was identified from flowering dogwood fruit that gave consistent EAD activity. In a flight tunnel assay there was no significant difference in the response of individual dogwood flies exhibiting upwind anemotactic flight to volatile extracts from dogwood fruit and the six-component synthetic mixture. Dogwood flies also displayed significantly greater levels of upwind flight to sources with the dogwood volatile blend than with previously identified volatile blends from domestic apple or hawthorn fruit. Selected subtraction assays showed that the three-component mixture of 3-methylbutan-1-ol, 1-octen-3-ol, and beta-caryophyllene elicited levels of upwind flight to the source equivalent to the six-component mixture. Our study adds to previous ones showing that populations of Rhagoletis pomonella flies infesting apple, hawthorn, and flowering dogwood fruit are attracted to unique mixtures of fruit volatiles, supporting the hypothesis that host fruit odors could be key traits in sympatric host shifts and establishing host fidelity within members of the Rhagoletis pomonella species complex.

Animals↗

PubMed2004

First identification of a putative sex pheromone in a praying mantid.

Praying mantids are models for a wide variety of behavioral, physiological, and ecological studies, and sex pheromones have been assumed to be important components of their biology. However, no mantid pheromone has ever been identified. We collected volatiles emitted by females of the mantid, Sphodromantis lineola, via solid phase microextraction (SPME). Mass spectral analysis revealed the collected volatiles to be a mixture of pentadecanal and tetradecanal. We prepared a synthetic mixture of these compounds, and found that males were both attracted to this mixture and stimulated to exhibit typical precopulatory behavior. We then examined male antennae with scanning electron microscopy, and confirmed the presence of porous antennal sensilla typical of insect pheromone receptors, i.e., that male mantids are equipped with the appropriate morphological apparatus to receive volatile chemical signals. Pheromones, in conjunction with visual and tactile cues, are thus an important feature of the reproductive biology of this, and undoubtedly other species of mantids. In addition to adding a crucial aspect of behavioral biology to our knowledge of this group, identification and synthesis of mantid pheromones may be a first step in attracting and aggregating these generalist predators for use in pest control.

Animals↗

PubMed2004

Volatiles associated with preferred and nonpreferred hosts of the Nantucket pine tip moth, Rhyacionia frustrana.

Ovipositing female Nantucket pine tip moth, Rhyacionia frustrana, prefer loblolly pine, Pinus taeda L., to slash pine, Pinus elliottii Engelm, except during the first spring following planting of seedlings. Host discrimination by R. frustrana increases as seedlings develop, suggesting that changes in the chemical composition of seedlings may mediate the moth's host preferences. Volatile compounds from slash and loblolly pine seedlings were collected using solid-phase microextraction (SPME) during the first year following planting. Four collection periods coincided with adult emergence and oviposition during each of four annual generations of R. frustrana in the Georgia Coastal Plain. Infestation of slash pine peaked during the second tip moth generation and was similar to the loblolly pine infestation level. By the fourth tip moth generation, slash pine infestation levels had declined and diverged considerably from those of loblolly pine. Significant differences in relative quantities of beta-pinene, alpha-phellandrene, limonene, beta-phellandrene, bornyl acetate, beta-caryophyllene, and an unidentified sesquiterpene occurred between slash and loblolly pine during the fourth generation. However, no strong correlation was observed between any individual compound and host damage that could readily explain the temporal changes in R. frustrana host preference. Gas chromatographic-electroantennographic detection (GC-EAD) analyses of standards identified 19 different seedling-associated compounds that elicited antennal responses from R. frustrana females, indicating that a blend of terpenoids may mediate host discrimination.

Animals↗

PubMed2004

Avian exocrine secretions. I. Chemical characterization of the volatile fraction of the uropygial secretion of the green woodhoopoe, Phoeniculus purpureus.

Using gas chromatography-mass spectrometry in conjunction with auxiliary techniques such as solid phase microextraction and determination of double bond positions by means of dimethyl disulfide derivatization, 45 constituents of the uropygial secretion of the green woodhoopoe, Phoeniculus purpureus, have been identified. The majority of these constituents are long-chain branched and unbranched alkanes, and (Z)-alkenes such as (Z)-9-tricosene, and a number of unidentified wax esters. The more volatile fraction of the secretion contained short-chain fatty acids, aldehydes, aliphatic and heterocyclic aromatic amines, ketones, and dimethyl sulfides. This group of volatile compounds is responsible for the obnoxious odor of the secretion and also for its defensive action against predators.

Aldehydes↗

PubMed2001

Volatile hydrocarbon biodegradation by a mixed-bacterial culture during growth on crude oil.

Volatile hydrocarbon biodegradation by a mixed-bacterial culture during growth on Bow River crude oil was investigated using solid phase microextraction (SPME). Inoculum treatments were examined in relation to C(5)-C(11) hydrocarbon degradation. Up to 1600 mg/l biomass (dry weight) was tested without achieving significant volatile hydrocarbon partitioning and affecting analysis. Inoculum age rather than concentration had the most profound impact on biodegradation. When late log phase crude oil-grown inocula were used, C(5)-C(11) biodegradation reached 55-60%; methylcyclohexane and other branched compounds eluting before n-C(8) were recalcitrant. Increasing the late log inoculum concentration from 0.63 to 63 mg/l resulted in a twofold increase in degradation rate without improving the substrate range. Methylcyclohexane recalcitrance was correlated with reduced levels of hydrocarbon-degrading bacteria and volatile hydrocarbon evaporation from the inoculum flasks. A decreased lag phase prior to degradation was observed when using early stationary phase cultures as inocula and most compounds up to C(11), including methylcyclohexane, were biodegraded.

Bacteria↗

PubMed2000

Degradation of chlortoluron in water disinfection processes: a kinetic study.

The kinetics of the reaction between chlortoluron, a phenylurea herbicide [N'-(2-hydroxy-4-methyl-5-chlorophenyl)-N,N-dimethylurea], and hypochlorite, the active species in water disinfection processes involving chlorine, were investigated by HPLC-UV and HPLC-electrospray ionisation mass spectrometry (HPLC-ESI-MS). In particular, the concentrations of the main chlortoluron by-products were monitored as a function of time by HPLC-ESI-MS and a kinetic model was developed to fit the relevant curves. The results showed that chlortoluron degradation starts with two parallel pathways, namely, chlorination and hydroxylation of the aromatic ring, which are then followed by consecutive chlorination reactions, and after almost 2 weeks by ring opening and partial mineralisation, as confirmed by head-space solid-phase microextraction gas chromatography-MS (SPME-GC-MS) and total organic carbon (TOC) measurements. Kinetic constants for the first reactions of the overall process, under pseudo-first-order conditions (hypochlorite excess), were estimated by a fitting procedure.

Chromatography, High Pressure Liquid↗

PubMed2002

Strategically designed sample composition for fastest screening of polychlorinated biphenyl congeners in water samples.

A new strategy for preparing composite samples of special interest and applicability in environmental screening studies is presented. The use of supersaturated experimental design matrices to conduct the sample composition of water sample specimens in screening studies is demonstrated. In contrast to well known conventional sample composition, this strategic approach provides analytical objects allowing the accurate prediction of analyte concentration levels in the original individual sample specimens while fixing the number of experiments to be carried out down to the very number of sample specimens. This will be of special importance when dealing with analytes that require complicated, labour intensive and expensive analytical processes. To reach this goal, two main conditions must be fulfilled. The first one is the sparsity effect (Pareto principle) which holds for the specimens in the sampling campaign. This means that the number of really anomalous or contaminated specimens, as compared to the total number of specimens to be analysed, is low. In environmental screening studies, frequently this situation can be reasonably assumed. The second condition is to have an effective manner to develop and solve the experimental designs required to build-up the composite samples. The challenging problem of screening PCBs in water samples has been tackled to show the usefulness of this strategic approach by combining chemometrically assisted sample composition and rapid analysis using solid-phase microextraction of the composite samples.

Environmental Monitoring↗

PubMed2003

Analysis of BTEX and other substituted benzenes in water using headspace SPME-GC-FID: method validation.

The analysis of BTEX and other substituted benzenes in water samples using solid phase microextraction (SPME) and quantification by gas chromatography with flame ionization detection (GC-FID) was validated. The best analytical conditions were obtained using PDMS/DVB/CAR fibre using headspace extraction (HS-SPME) at 50 [degree]C for 20 min without stirring. The linear range for each compound by HS-SPME with GC/FID was defined. The detection limits for these compounds obtained with PDMS/DVB/CAR fibre and GC/FID were: benzene (15 ng L(-1)), toluene (160 ng L(-1)), monochlorobenzene (54 ng L(-1)), ethylbenzene (32 ng L(-1)), m-xylene (56 ng L(-1)), p-xylene (69 ng L(-1)), styrene (35 ng L(-1)), o-xylene (42 ng L(-1)), m-dichlorobenzene (180 ng L(-1)), p-dichlorobenzene (230 ng L(-1)), o-dichlorobenzene (250 ng L(-1)) and trichlorobenzene (260 ng L(-1)). This headspace SPME-GC-FID method was compared with a previously validated method of analysis using closed-loop-stripping analysis (CLSA). The headspace SPME-GC-FID method is suitable for monitoring the production and distribution of potable water and was used, in field trials, for the analysis of samples from main intakes of water (surface or underground) and from the water supply system of a large area (Lisbon and neighbouring municipalities).

Chromatography, Gas↗

PubMed2003

Solid phase micro-extraction in a miniature ion trap mass spectrometer.

Fiber introduction mass spectrometry (FIMS), a variation of solid-phase microextraction (SPME) and membrane introduction mass spectrometry (MIMS), is employed with a miniature mass spectrometer. The inlet system, constructed of commercially available vacuum parts, allows the direct introduction of the SPME needle vacuum chamber into the mass spectrometer. Thermal desorption of the analyte from the poly(dimethylsiloxane) (PDMS) coated fiber was achieved with a built in nichrome heater, followed by electron ionization of the analytes internal to the cylindrical ion trap (CIT). The system has been tested with several volatile organic compounds (VOC) in air and to analyze the headspace over aqueous solutions, with limits of detection in the low ppb range. The signal rise (10-90%) and fall (90-10%) times for the system ranged from 0.1 to 1 s (rise) and 1.2 to 6 s (fall) using heated desorption. In addition, this method has been applied to quantitation of toluene in benzene, toluene, xylene (BTX) mixtures in water and gasoline. This simple and rapid analysis method, coupled to a portable mass spectrometer, has been shown to provide a robust, simple, rapid, reproducible, accurate and sensitive (low ppb range) fieldable approach to the effective in situ analysis of VOC in various matrices.

Ions↗

PubMed2003

On-site monitoring of biogenic emissions from Eucalyptus dunnii leaves using membrane extraction with sorbent interface combined with a portable gas chromatograph system.

Membrane extraction with sorbent interface, combined with a portable gas chromatograph system (MESI-Portable GC) for continuous on-line monitoring of biogenic volatile organic compounds (BVOCs) emissions (from leaves of Eucalytus dunnii in a greenhouse), is presented herein. A sampling chamber was designed to facilitate the extraction and identification of the BVOCs emitted by the Eucalytus dunnii leaves. Preliminary experiments, including; enrichment times, microtrap temperatures, stripping gas flow rates, and desorption temperatures were investigated to optimize experimental parameters. The main components of BVOCs released by the Eucalytus dunnii leaves were identified by comparing the retention times of peaks with those of authentic standard solutions. They were then confirmed with solid phase microextraction coupled with gas chromatography and mass spectrometry (SPME-GC-MS). BVOC emission profiles of [small alpha]-pinene, eucalyptol, and [gamma]-terpinene emitted by intact and damaged Eucalytus dunnii leaves were obtained. The findings suggest that the MESI-Portable GC system is a simple and useful tool for field monitoring changes in plant emissions as a function of time.

Chromatography, Gas↗

PubMed2004

Modelling SPME data from kinetic measurements in complex samples.

The kinetics of the partition process to solid phase microextraction fibres is often modelled using a stagnant layer model. Despite its usefulness, in some agitation systems such a model cannot be applied because the stagnant layer cannot be characterized precisely. Therefore, in this present study an alternative approach is introduced. Transport from the bulk medium to the fibre coating is simply modelled by a finite mass transfer coefficient instead of diffusion through a stagnant water layer surrounding the fibre. Intra-fibre transport is described by non-steady diffusion. The model is aimed at the analysis of SPME measurements in the kinetic phase for samples including a binding matrix. It was validated with experimental results of SPME measurements concerning the absorption kinetics of [(3)H]estradiol at different concentrations of bovine serum albumin (BSA) as a chemical binding matrix. The model provides excellent fits of the experimental data, resulting in an association constant (K(a)) of estradiol for BSA of 5.66 x 10(4) M(-1), which is similar to literature values and a fibre coating/bulk medium partition coefficient of 5.0 x 10(3). The kinetics of extraction were studied with the model, showing that the rate-limiting step in the extraction process was the diffusion in the fibre. This finding rules out the possibility that the presence of the matrix itself in the diffusion layer affects the kinetics of estradiol uptake into the SPME fibre.

Absorption↗

PubMed2005

Improved detection of low vapor pressure compounds in air by serial combination of single-sided membrane introduction with fiber introduction mass spectrometry (SS-MIMS-FIMS).

The use of two methods in tandem, single-sided membrane introduction mass spectrometry (SS-MIMS) and fiber introduction mass spectrometry (FIMS), is presented as a technique for field analysis. The combined SS-MIMS-FIMS technique was employed in both a modified commercial mass spectrometer and a miniature mass spectrometer for the selective preconcentration of the explosive simulant o-nitrotoluene (ONT) and the chemical warfare agent simulant, methyl salicylate (MeS), in air. A home-built FIMS inlet was fabricated to allow introduction of the solid-phase microextraction (SPME) fiber into the mass spectrometer chamber and subsequent desorption of the trapped compounds using resistive heating. The SS-MIMS preconcentration system was also home-built from commercial vacuum parts. Optimization experiments were done separately for each preconcentration system to achieve the best extraction conditions prior to use of the two techniques in combination. Improved limits of detection, in the low ppb range, were observed for the combination compared to FIMS alone, using several SS-MIMS preconcentration cycles. The SS-MIMS-FIMS response for both instruments was found to be linear over the range 50 to 800 ppb. Other parameters studied were absorption time profiles, effects of sample flow rate, desorption temperature, fiber background, memory effects, and membrane fatigue. This simple, sensitive, accurate, robust, selective, and rapid sample preconcentration and introduction technique shows promise for field analysis of low vapor pressure compounds, where analyte concentrations will be extremely low and the compounds are difficult to extract from a matrix like air.

Air Pollutants↗