Comprehensive Two-Dimensional Gas Chromatography for Analysis of Volatile Compounds in Foods and Beverages

A cromatografia gasosa bidimensional abrangente (GC×GC) é uma técnica analítica relativamente nova, que tem sido amplamente empregada para análise de vários tipos de amostras complexas. A GC×GC proporciona maior capacidade de pico, sensibilidade e resolução, quando comparada à cromatografia gasosa monodimensional (1D-GC). Além disso, a estruturação dos cromatogramas bidimensionais auxilia na identificação de classes de compostos. No que diz respeito à análise de alimentos e bebidas, a eficiência superior da GC×GC resulta em benefícios únicos quando comparada às técnicas analíticas disponíveis para os mais variados objetivos de análise: separação de grupos de compostos aroma-ativos, verificação de perfil cromatográfico, análise de compostos alvo ou identificação de componentes desconhecidos. Quando compostos aroma-ativos estão presentes em nível de traços, a GC×GC também pode ser empregada como uma técnica de alto potencial devido a sua sensibilidade superior. Tendo em vista que a fração volátil de muitos alimentos e bebidas pode determinar a aceitação ou rejeição destes produtos por parte do consumidor, a caracterização da mesma pode ser feita com base na composição destes compostos voláteis. Neste trabalho, as aplicações da GC×GC para análise de voláteis em alimentos e bebidas são apresentadas, desde a fase inicial de sua implementação até 2010. Alguns tópicos relacionados aos princípios da GC×GC foram também discutidos.Comprehensive two-dimensional gas chromatography (GC×GC) is a relatively new analytical technique, which has been widely used for the analysis of a variety of complex samples. GC×GC offers increased peak capacity, higher sensitivity, and improved resolution when compared to conventional one-dimensional gas chromatography (1D-GC). In addition, it generates structured two-dimensional chromatograms, which aids in the identification of compound classes. The enhanced separation provided by GC×GC has been a distinctive benefit when it is compared to other available analytical techniques that deal with the analysis of food and beverages, irrespective of the goal of the analysis, i.e. aroma group-type separation and fingerprinting, target-volatile compound analysis or identification of unknowns. When trace amounts of aroma active compounds are present, GC×GC may also be used as a very powerful tool for their analysis due to its higher sensitivity. As volatile fractions may determine the acceptance or rejection of many foods and beverages by the consumer, the characterization of these products may be done having volatile composition as a basis. Applications of GC×GC for the analysis of volatiles of foods and beverages were revised since the emergence of this technique until 2010. Some topics related to principles of GC×GC were also discussed

Aplicação da cromatografia gasosa bidimensional abrangente com microdetector de captura de elétrons para determinação de agrotóxicos em sedimentos

Analysis of seven pesticides in sediments was successfully achieved using comprehensive two-dimensional gas chromatography with micro-electron capture detection, as it provided higher sensitivity and less matrix interference. Repeatability and intermediate precision of peak areas and heights were less than 4% and the recovery percentage for the analytes ranged from 52 to 115%. Instrumental LOD and LOQ were in the range of 0.60 to 2.31 μg L-1 and 1.83 to 5.62 μg L-1, respectively. Concentrations of 3.34 μg kg-1 (dry basis) for trifloxystrobin and azoxystrobin (below the LOQ) were found in a sediment sample

Volatile compounds of Baccharis punctulata, Baccharis dracunculifolia and Eupatorium laevigatum obtained using solid phase microextraction and hydrodistillation

In this work the qualitative chromatographic profiles of the volatile oil obtained with fresh chopped leaves of Baccharis punctulata, Baccharis dracunculifolia and Eupatorium laevigatum, using HS-SPME were compared with their hydrodistilled oils. Several Brazilian native plant species have not yet been studied regarding their volatile compounds composition. Conventional techniques employed for the investigation of volatile compounds, such as hydrodistillation, may impart chemical changes to the original oil composition. The use of HS-SPME provides alternative milder extraction conditions, preventing chemical transformations and supplying complementary information about volatiles composition. Coumarin and coumaran were detected by the first time among volatile components of E. laevigatum leaves after mechanical damage, only when using HS-SPME. Differences and similarities perceived between volatile compounds profiles using both extraction techniques are discussed, showing that they are complementary and may bring insight about fresh leaf volatiles playing infochemical roles and about chemical transformations caused by hydrodistillation

Desenvolvimento de métodos analíticos para determinação de agrotóxicos em sedimentos por cromatografia gasosa monodimensional e bidimensional abrangente com micro detector de captura de elétrons

The development of analytical methods for determination of eight pesticides of different chemical classes (trichlorfon, propanil, fipronil, propiconazole, trifloxystrobin, permethrin, difenoconazole and azoxystrobin) in sediments with gas chromatography-micro-electron capture detector (GC/µECD) and comprehensive two-dimensional gas chromatography with micro-electron capture detector (GCxGC/µECD) is described. These methods were applied to real sediment samples, and the best results were obtained using a 5% diphenyl-methylpolysiloxane column for 1D-GC. For GCxGC the same column was employed in the first dimension and a 50%-phenyl-methylpolysiloxane stationary phase was placed in the second dimension. Due to the superior peak capacity and selectivity of GCxGC, interfering matrix peaks were separated from analytes, showing a better performance of GCxGC

Structural and Chemical Profiles of Myrcia splendens (Myrtaceae) Leaves Under the Influence of the Galling Nexothrips sp. (Thysanoptera)

Thysanoptera-induced galls commonly culminate in simple folding or rolling leaf gall morphotypes. Most of these galls are induced by members of the suborder Tubulifera, with only a few species of the suborder Terebrantia being reported as gall inducers. The Terebrantia, as most of the gall inducers, manipulates the host plant cellular communication system, and induces anatomical and biochemical changes in its host plant. In an effort to keep its homeostasis, the host plant reacts to the stimuli of the galling insect and triggers chemical signaling processes. In contrast to free-living herbivores, the signaling processes involving galling herbivores and their host plants are practically unknown. Current investigation was performed into two steps: first, we set the structural profile of non-galled and galled leaves, and looked forward to find potential alterations due to gall induction by an undescribed species of Nexothrips (suborder Terebrantia) on Myrcia splendens. Once oil glands had been altered in size and number, the second step was the investigation of the chemical profile of three tissue samples: (1) non-galled leaves of a control individual, (2) non-galled leaves of galled plants, and (3) galls. This third sample was divided into two groups: (3.1) galls from which the inducing thrips were manually removed and (3.2) galls macerated with the inducing thrips inside. The chemical profile was performed by gas chromatography/ mass spectrometric detector after headspace solid-phase extraction. The galling activity of the Nexothrips sp. on M. splendens culminates in mesophyll compactness interspersed to diminutive hypersensitive spots, development of air cavities, and the increase in size and number of the secretory glands. Seventy-two compounds were completely identified in the volatile profile of the three samples, from which, sesquiterpenes and aldehydes, pertaining to the “green leaf volatile” (GLVs) class, are the most abundant. The rare event of gall induction by a Terebrantia revealed discrete alterations toward leaf rolling, and indicated quantitative differences related to the plant bioactivity manipulated by the galling thrips. Also, the content of methyl salicylate has varied and has been considered a potential biomarker of plant resistance stimulated as a long-distance effect on M.splendens individuals

Differentiation of wines according to grape variety using multivariate analysis of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection data

AbstractHeadspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GC×GC/TOFMS) was used to analyse the volatiles in five types of wines elaborated with grapes of Cabernet Sauvignon, Merlot, Chardonnay, Sauvignon Blanc and Pinot Noir varieties. Fisher ratio, principal component analysis (PCA) and stepwise linear discriminant analysis (SLDA) were used to develop a discriminant model and, as a result, 12 volatile compounds enabled differentiation and classification of wines according to grape cultivars. A detailed examination of GC×GC/TOFMS data showed that the use of one-dimensional gas chromatography with a mass spectrometric detector (1D-GC/MS) would probably result in misidentification of some of these 12 compounds, as they showed partial coelution with other components in the first chromatographic dimension

Efeito do óleo essencial da erva de Santa-Maria (Chenopodium ambrosiodes Linnaeus, 1753) sobre camundongos suíços (Mus musculus Linnaeus, 1758) não infectados e infectados com Plasmodium berghei Vincke & Lips, 1948

Abstract. Effect of the essential oil of Santa-Maria herb (Chenopodium ambrosiodes Linnaeus, 1753)on swiss mices (Mus musculus Linnaeus, 1758) non-infected and infected with Plasmodium bergheiVincke & Lips, 1948