Two-dimensional Gas Chromatography-quadrupole Mass Spectrometry Research Articles

Retinoid receptors and metabolism in endocrine disruption

We investigated the occurrence of disinfection by-products (DBPs) with genotoxic potential in plant effluent and distribution water samples from four drinking water treatment plants in two Chinese cities using comprehensive two-dimensional gas chromatography–quadrupole mass spectrometry. We tested the samples for 37 DBPs with genotoxic potential, which we had previously identified and prioritized in water under controlled laboratory conditions. Thirty of these DBPs were found in the water samples at detection frequencies of between 10% and 100%, and at concentrations between 3.90 and 1.77 × 103 ng/L. Of the DBPs detected, the concentrations of 1,1,1-trichloropropan-2-one were highest, and ranged from 299 to 1.77 × 103 ng/L with an average of 796 ng/L. The concentrations of 6-chloro-2-N-propan-2-yl-1,3,5-triazine-2,4-diamine and 2,6-ditert-butylcyclohexa-2,5-diene-1,4-dione were also much higher, and ranged from 107 to 721 ng/L, and from 152 to 504 ng/L, respectively. Concentrations of 1,1,1-trichloropropan-2-one, 2-chloro-1-phenylethanone, 2,2-dichloro-1-phenylethanone and 6-chloro-2-N-propan-2-yl-1,3,5-triazine-2,4-diamine were highest at or near the treatment plants and decreased with increasing distance from the plants. Patterns in the concentrations of benzaldehyde, 2-phenylpropan-2-ol, and 1-methylnaphthalene differed between plants. The levels of DBPs such as 4-ethylbenzaldehyde, (E)-non-2-enal, and 1-phenylethanone were relatively constant within the distribution systems, even at the furthest sampling points (20 km < d < 30 km). A risk assessment showed that there was no risk to human health. It is, however, important to note that, because of limited availability of toxicity data, only five DBPs were evaluated in this study. The risks to health associated with exposure to the target potentially genotoxic DBPs should not be ignored because of their prolonged existence in drinking water.

Two-dimensional gas chromatographic profiling as a tool for a rapid screening of the changes in volatile composition occurring due to microoxygenation of red wines

Microoxygenation (MOX) is a widely applied technique to deliver continuously trace amounts of oxygen to red wine during vinification and ageing in order to improve color stability and sensory properties. Proven by sensory means, the added oxygen modifies not only tannin structure and color of the wines, but also their composition of volatiles. In this study different microoxygenation treatments prior and after malolactic fermentation were carried out for Pinot noir, Cabernet Sauvignon and Dornfelder wines of the 2007 vintage. Volatile components of subsequent wines were analyzed using headspace-solid phase microextraction coupled to comprehensive two-dimensional gas chromatography–quadrupole mass spectrometry (GC × GC–qMS). Quantitative data were retrieved from two-dimensional images obtained from GC × GC chromatograms of volatile compounds applying a software package, which is commonly used in the field of proteomics for two-dimensional electrophoresis gels. This approach revealed a discrimination of the applied treatments by multivariate statistics based on volatiles alone, such as the clear distinction among wines treated before or after malolactic fermentation in case of Cabernet Sauvignon and Dornfelder or the effect of different oxygen doses. Besides the differentiation of MOX treatments from the untreated control, specific varietal and technological effects could be distinguished. The image processing of the GC × GC data offered valuable tools which were able to identify those areas in the 2D images that were most responsible for discrimination among different MOX treatments. Based on the loadings of individual aroma compounds a set of markers for the MOX-induced modifications of volatiles could be suggested.

Optimized use of a 50 μm ID secondary column in comprehensive two-dimensional gas chromatography–mass spectrometry

The objective of the present research is directed towards the optimized use of a 50 μm ID secondary column, in a comprehensive two-dimensional gas chromatography–quadrupole mass spectrometry (GC × GC–qMS) system. The analytical aim was achieved by exploiting a split-flow GC × GC approach, and a rapid-scanning qMS instrument. The stationary phase combination consisted of an apolar (silphenylene polymer) 30 m × 0.25 mm ID column, linked by means of a Y-union, to an MS-connected 1 m × 0.05 mm ID polar one [poly(ethyleneglycol)], and to a 0.20 m × 0.05 mm ID uncoated capillary segment; the latter was connected to a manually operated split-valve. It will be herein demonstrated that the split-flow GC × GC approach, successfully employed in previous H 2-based, flame ionization detection experiments, provides equally satisfactory results using mass spectrometric detection and helium as carrier gas. An optimized split-flow GC × GC–qMS method was developed and exploited for the analysis of a perfume sample. The results attained were compared with those observed using the same analytical column combination, but with no flow-splitting. It was found that it is not convenient to employ a 50 μm ID secondary column in a conventional GC × GC–MS instrument. On the contrary, the use a 50 μm ID secondary column, in a split-flow, twin-oven system, provided a good performance. A recently developed comprehensive chromatography software was used for data processing.