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At least 559 records · Page 31Linked to original sources
PubMed2003

Identification of aroma active compounds in orange essence oil using gas chromatography-olfactometry and gas chromatography-mass spectrometry.

Using GC-MS and GC-flame ionization detection (FID)/olfactometry, 95 volatile components were detected in orange essence oil, of which 55 were aroma active. In terms of FID peak area the most abundant compounds were: limonene, 94.5%; myrcene, 1%; valencene, 0.8%; linalool, 0.7%, and octanal, decanal, and ethyl butyrate, 0.3% each. One hundred percent of the aroma activity was generated by slightly more than 4% of the total volatiles. The most intense aromas were produced by octanal, wine lactone, linalool, decanal, beta-ionone, citronellal, and beta-sinensal. Potent aroma components reported for the first time in orange essence oil include: E-2-octenal, 1-octen-3-ol, Z-4-decenal, E,E-2,4-nonadienal, guaiacol, gamma-octalactone, and m-cresol. Over 20 compounds were identified for the first time in orange essence oil using MS, however, most did not exhibit aroma activity.

Citrus↗
PubMed2000

Comparison of gas chromatography-pulsed flame photometric detection-mass spectrometry, automated mass spectral deconvolution and identification system and gas chromatography-tandem mass spectrometry as tools for trace level detection and identification.

The complexity of a matrix is in many cases the major limiting factor in the detection and identification of trace level analytes. In this work, the ability to detect and identify trace level of pesticides in complex matrices was studied and compared in three, relatively new methods: (a) GC-PFPD-MS where simultaneous PFPD (pulsed flame photometric detection) and MS analysis is performed. The PFPD indicates the exact chromatographic time of suspected peaks for their MS identification and provides elemental information; (b) automatic GC-MS data analysis using the AMDIS ("Automated Mass Spectral Deconvolution and Identification System") software by the National Institute of Standards and Technology; (c) GC-MS-MS analysis. A pesticide mixture (MX-5), containing diazinon, methyl parathion, ethyl parathion, methyl trithion and ethion was spiked, in descending levels from 1 ppm to 10 ppb, into soil and sage (spice) extracts and the detection level and identification quality were evaluated in each experiment. PFPD-MS and AMDIS exhibited similar performance, both superior to standard GC-MS, revealing and identifying compounds that did not exhibit an observable GC peak (either buried under the chromatographic background baseline or co-eluting with other interfering GC peaks). GC-MS-MS featured improved detection limits (lower by a factor of 6-8) compared to AMDIS and PFPD-MS. The GC-PFPD-MS-MS combination was found useful in several cases, where no reconstructed ion chromatogram MS-MS peaks existed, but an MS-MS spectrum could still be extracted at the elution time indicated by PFPD. The level of identification and confirmation with MS-MS was inferior to that of the other two techniques. In comparison with the soil matrix, detection limits obtained with the loaded sage matrix were poorer by similar factors for all the techniques studied (factors of 5.8, >6.5 and 4.0 for AMDIS, PFPD-MS and MS-MS, respectively). Based on the above results, the paper discusses the trade-offs between detectivity and identification level with the compared three techniques as well as other more traditional techniques and approaches.

Automation↗
PubMed2000

Analysis of steroids in environmental water samples using solid-phase extraction and ion-trap gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry.

This paper describes an improved method for the extraction and determination of three steroids, oestrone, 17beta-oestradiol, and the synthetic contraceptive steroid 17alpha-ethinyloestradiol in aqueous matrices. Samples of wastewater and environmental water were spiked with internal standards, comprising isotopically labelled analogues of the steroids to be determined. The samples were extracted using solid-phase extraction disks and the extracts were then derivatized to form tert.-butyldimethylsilyl derivatives. The derivatised steroids were determined in the final extracts by GC-MS or GC-MS-MS allowing an operational detection limit for each steroid in effluent samples of 1 ng l(-1).

Chromatography, Gas↗
PubMed2003

Determination of 13C and 15N enrichments of urea in plasma by gas chromatography-combustion isotope ratio mass spectrometry and gas chromatography-mass spectrometry using the 2-methoxypyrimidine derivative.

We describe a GC-MS and GC-c-IRMS method for the determination of labeled urea tracer enrichments in plasma as a result of combined 13C- and 15N(2)-urea infusion experiments in piglets. Urea was converted into 2-methoxypyrimidine, a stable derivative, suited for analyses by both GC-MS and GC-c-IRMS. Using calibration curves for the respective working ranges (13C-urea: 0-1% APE; 15N(2)-urea: 0-7% MPE) enrichments were established in single point measurements; for 15N(2)-urea as values+/-0.15% MPE (95% confidence interval); for 13C-urea as values+/-0.02% APE (95% confidence interval). 15N(1)-urea enrichments were determined by measurement of the same sample with GC-c-IRMS and GC-MS. Subtraction of the 13C specific GC-c-IRMS data from the nondiscriminating GC-MS data for the sum of 13C- and 15N(1)-urea resulted in 15N(1)-urea enrichments+/-0.15% MPE (95% confidence interval). Application of the method in a combined 13C-urea bolus and 15N(2)-urea primed constant infusion experiment in piglet was demonstrated.

Animals↗
PubMed1998

Rapid preconcentration method for the determination of pyrethroid insecticides in vegetable oils and butter fat and simultaneous determination by gas chromatography-electron capture detection and gas chromatography-mass spectrometry.

A simple and rapid solid-phase extraction (SPE)-GC method for the preconcentration and quantification of pyrethroids at low nanogram levels in oils and high fat content samples is presented. The method was studied using seven highly persistent pyrethroid insecticides, viz., cypermethrin, deltamethrin, fenvalerate, cyfluthrin, allethrin, cyhalothrin and permethrin. Preconcentration was achieved by treating the oil samples with methyltrioctylammonium chloride and subsequent elution of the pyrethroid molecules from a graphitized carbon black SPE cartridge using 5 ml of acetonitrile. Pyrethroid quantification was achieved by GC with electron capture detection. Recoveries of the pyrethroids at fortification levels of 0.05-0.5 ppm were 94-105%. Storage on graphitized carbon black for 30 d lowered the recovery of the pyrethroids by only 3-6%. The method compared well with results obtained by a GC-MS method. The relative standard deviation at a concentration level of 0.05-0.2 microgram ml-1 ranged from 1.31 to 5.16%. The limit of detection achieved was 0.002 microgram ml-1 without any additional clean-up and with little interference from lipids during analysis.

Animals↗