Multidimensional Gas Chromatography-mass Spectrometry Research Articles

2-(2-Butenylidene)-3,3-dimethyl-5-(2-oxopropyl)tetrahydrofuran: A New Degradation Product of 3-Hydroxy-5,6-epoxy-.beta.-ionol

Identification of 2-(2-butenylidene)-3,3-dimethyl-5-(2-oxopropyl)tetrahydrofuran diastereomers (4, 5) in various leaves [stinging nettle; sloe tree; strawberry; vine (Riesling); sweet silique (Bunias orientalis)] was achieved by comparison of HRGC retention and spectral (MS; vapor phase FTIR) data with those of synthetic references. Model experiments revealed their acid-catalyzed formation from 3-hydroxy-5,6-epoxy-β-ionol that was present in glycosidically bound form in the above-mentioned leaves. Assignment of the isomers 4a/4b and 5a/5b was established by NOE experiments. Enantiodifferentiation carried out by on-line coupled multidimensional gas chromatography-mass spectrometry revealed the occurrence of enantiomerically pure 5S enantiomers 4b/5b in the natural sources

Coplanar polychlorinated biphenyls in some Finnish food commodities

Toxic non- ortho-chlorine substituted, or coplanar, PCB congeners were determined in a set of standard food commodities of animal origin obtained from stores in the capital area. Using multidimensional gas chromatography and low resolution mass spectrometry in EI and NCI modes for detection of these compounds it was observed that coplanar PCBs are present at measurable concentrations in all foods analyzed. The concentration of PCB 77 ranges from a few to several tens of pg/g, calculated on fresh weight basis; PCB 126 is typically present at low pg/g level and is responsible for 38...74 % of the toxic equivalent (TEQ) burden of these congeners. The average daily TEQ intake from coplanar PCB compounds is estimated to be 170 pg/person and it is concluded that the TEQ intake of a typical consumer originating from coplanar PCBs exceeds that from chlorinated dibenzodioxins and -furans.

Additional volatile constituents of Artemisia vulgaris l. herb

AbstractThe extract obtained by solid‐liquid extraction with pentane‐dichloromethane (2+1, v/v) from dry mugwort (Artemisià vulgaris L.) herb was fractionated by means of gel permeation chromatography (GPC) and subsequent middle‐pressure liquid chromatography (MPLC). Capillary gas chromatography (HRGC) and combined HRGC techniques, i.e. HRGC‐mass spectrometry (HRGC‐MS) and HRGC‐Fourier transform infrared spectroscopy (HRGC‐FTIR) of the separated MPLC fractions revealed the occurrence of 54 additional volatiles not described as yet in A. vulgaris herb. Among them, chiral evaluation of y‐nonalactone carried out by on‐line coupled multidimensional gas chromatography‐mass spectrometry (MDGC‐MS) revealed a distribution of (R): (S) = 34:66%.

Bound aroma compounds from the fruit and the leaves of blackberry (Rubus laciniata L.)

HRGC and HRGC-MS identifications of bound aroma compounds from the fruit and the leaves of blackberry (Rubus laciniata L.) were achieved after isolation of extracts obtained by Amberlite XAD-2 adsorption and methanol elution followed by hydrolysis with a commercial pectinase enzyme. In the fruit 41 aglycons and in the leaves 32 bound aroma compounds were identified. Quantitative HRGC revealed 5.8 mg/kg of aglycons in the fruit, whereas 56.1 mg/kg were determined in the leaves. Major constituents comprised benzyl alcohol, benzoic acid, 3-hydroxy-7,8-dihydro-beta-ionol, (Z)-3-hexen-1-ol, and the diastereomeric vitispiranes. Chiral evaluation of enzymatically liberated aroma compounds carried out by on-line multidimensional capillary gas chromatography-mass spectrometry (MDGC-MS) revealed the occurrence of enantiomerically pure (S)-2-heptanol both in the fruits and in the leaves as well as 2-methyl-2-hepten-6-ol in the enantioselective distribution of R:S = 82:18% in the leaves.

Determination of toxic PCB congeners in biological samples by multidimensional gas chromatography-mass spectrometry (GC/GC/MS)

Multidimensional gas chromatography-mass spectrometry (GC/GC/MS) was used for the determination of coplanar PCB congeners in biological samples. A quadrupole low resolution mass spectrometer was used as the main detector in order to increase the reliability of identification and enable the use of 13C-labelled internal standards. The technique was capable to separate these toxic congeners from the complex matrix and decreased the need of sample purification.

Stereoselective formation of metabolites from 2-methyl-2-hepten-6-one by Botrytis cinerea

Controlled conversion of 2-methyl-2-hepten-6-one ( 1) by Botrytis cinerea resulted in the formation of ( S)-(+)-2-methyl-2-hepten-6-ol (sulcatol) ( 2) of 90% ee. In addition, (2 R, 5 R)- ( 3a), (2 S,5 S)- ( 3a′), (2 R,5 S)- ( 3b) and (2 S,5 R)-2-(1-hydroxy-1-methylethyl )-5-methyltetrahydrofuran ( 3b′), (3 s, 6 R)- ( 4a), (3 R,6 S)- ( 4a′), (3 R,6 R)- ( 4b) and (3 S,6 S)-tetrahydro-2,2,6-trimethyl-2 H-pyran-3-ol ( 4b′) as well as the diastereomeric dihydro-3-hydroxy-5-methyl-5-(2′-methyl-pent-2-en-5′-yl)-2(3 H)-furanones ( 5a/b) were found as biotransformations products of 1. Chiral analysis carried out by on-line multidimensional gas chromatography-mass spectrometry (MDGC-MS) revealed the following ee values: 46 % ( 3a); 80 % ( 3b); 56 % ( 4a); and 60 % ( 4b′). As confirmed by nOe experiments, 5a/b were formed in a ratio of 6:1.

Application of multidimensional gas chromatography—mass spectrometry to the determination of glycol ethers in air

The applicability of multidimensional gas chromatography—mass spectrometry to the analysis of five glycol ethers in air was demonstrated. Air samples were collected on charcoal tubes and desorbed with 5% methanol in methylene chloride as is described in method 1403 of the National Institute for Occupational Safety and Health Manual of Analytical Methods. The glycol ethers were determined by multidimensional gas chromatography—mass spectrometry. The limit of detection was 5 to 7 μg/sample for each compound.

Analysis of volatile organic compounds in polymers by dynamic headspace—multi-dimensional gas chromatography —mass spectrometry

The use of dynamic headspace—multi-dimensional gas chromatography—mass spectrometry in studies of volatile organic compounds in plastics is described. The results demonstrate the utility of this technique to increase the resolution of selected compounds, to generate less overlapped mass spectra and to obtain a higher confidence of the analysis results. Some construction features of the laboratory-assembled system are discussed.

Quantitation of the information content of multi-dimensional gas chromatography and low-resolution mass spectrometry in the identification of doping drugs

On the basis of information theory, a comparision of the performance of the identification of compounds by multi-dimensional gas chromatography and binary-encoded low-resolution mass spectrometry is made for doping drugs. This group of compounds was not selected at random but according to their pharmocoligical effects. For these compounds it was observed that the m/e values of the peaks in the mass spectra are highly correlated, while a number of chromatographic columns can be found on which the retention data are only slightly correlated. As a result, the information content of two-dimensional gas chromatographic retention data on such columns equals the information content of binary-encoded low-resolution mass spectra. It is shown that the accuracy and precision of retention data in gas-liquid chromatography, and therefore the information content, can be significantly improved if the data are corrected for adsorption effects of the solid support and extrapolated to a limiting value in the case of asymmetric peaks.