Carin von Mühlen

Comparative study of Eucalyptus dunnii volatile oil composition using retention indices and comprehensive two-dimensional gas chromatography coupled to time-of-flight and quadrupole mass spectrometry

In the present work, the composition of volatile oil from leaves of Eucalyptus dunnii was studied using comprehensive two-dimensional gas chromatography (GCxGC) techniques. Structurally related compounds were found to elute mainly in specific regions of the two-dimensional space, showing orderly distribution with chemical class. Mass spectra of essential oil components were obtained from two different mass spectrometry detection methods: quadrupole (qMS) and time-of-flight (TOFMS), using the same GCxGC system under the same chromatographic conditions. Higher values of Similarity (average S of 914 with TOFMS compared to 880 with qMS) and Reverse (average R of 944 with TOFMS compared to 881 with qMS) were obtained with GCxGC/TOFMS showing its superior performance, which was most likely due to better sensitivity and resolution arising from the TOFMS system, and lack of spectral bias. Also, the number of compounds found in E. dunnii essential oil was 15% higher when TOFMS was used. Most of these are lower abundance components or exhibit low quality mass spectra; this supports the improved sensitivity obtained with TOFMS. A linear relationship (r2=0.998) between experimental retention indices (LTPRI) of 30 standard compounds obtained with GCxGC/TOFMS and GC with flame ionization detection literature retention indices is reported as an aid for compound identification.

Retention indices in comprehensive two-dimensional gas chromatography

The identification of compounds by using gas chromatography (GC) in samples with significant complexity comprising a range of isomeric species, where characterization is based on peak retention times and mass spectra, generates uncertainty for the analyst. This leads to identification errors. The most reliable way to confirm the identification of each compound is based on authentic standard co-injection, which in several cases is economically prohibitive, and often unachievable in the time available for analysis. Retention index procedures are important tools to minimize misidentification of compounds in conventional chromatography. The introduction of comprehensive two-dimensional GC (GCu2009×u2009GC) for analysis of complex samples was a decisive step to increase the analytical capacity of chromatographic techniques. For many samples, the chromatographic resolution increase leads to quantitative expansion in the number of peaks identified, compared with conventional GC analysis. Notwithstanding this improved resolution, limitations still persist in correct peak identification, which suggests the use of retention indices may assist in supporting component identification in this important technique. In this work, approaches to use of the retention index in GCu2009×u2009GC are discussed, based on an evaluation of the literature in this area. Interpretation of effective chain length data for fatty acid methyl esters in the first and second dimensions is presented.

Analysis of organic compounds of water-in-crude oil emulsions separated by microwave heating using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry

In this work the higher peak capacity and resolution of comprehensive two-dimensional gas chromatography (GCxGC) has been successfully applied, for the first time, to tentatively identify several polar organic compounds of organic extracts of aqueous phases resulting from microwave demulsification process of water-in-crude oil emulsions. Results have shown that higher temperatures and longer exposure time to microwave irradiation produced water phases with a wider variety of polar organic compounds. The microwave process showed to be suitable for the extraction of several polar compounds classes of petroleum. The proposed microwave extraction method and GCxGC identification of polar compounds of petroleum samples are of practical interest for the petrochemical industry due to corrosion and related problems associated with these polar compounds in refinery equipments. The GCxGC/time-of-flight MS technique shows to be very important in the total separation of different classes of compounds and allows the identification of many compounds in these classes.

PYROLIGNEOUS LIQUOR PRODUCED FROM ACACIA MEARNSII DE WILD WOOD UNDER CONTROLLED CONDITIONS AS A RENEWABLE SOURCE OF CHEMICALS

Acacia mearnsii de Wild (black wattle) is one of the most important trees planted in Southern Brazil for tannin extraction and charcoal production. The pyrolysis of the black wattle wood used for obtaining charcoal is performed in brick ovens, with the gas fraction being sent directly into the environment. The present study examines the condensable compounds present in the liquor produced from black wattle wood at different thermal degradation conditions, using gas chromatography coupled with mass spectrometry (GC/MS). Branches of black wattle were thermally degraded at controlled ambient and temperature conditions. Overall, a higher variety of compounds were obtained under atmospheric air pressure than under synthetic air pressure. Most of the tentatively identified compounds, such as carboxylic acids, phenols, aldehydes, and low molecular mass lignin fragments, such as guayacol, syringol, and eugenol, were products of lignin thermoconversion. Substituted aromatic compounds, such as vanillin, ethyl vanillin, and 2-methoxy-4-propeny-phenol, were also identified. At temperatures above 200 oC, furan, 2-acetylfuran, methyl-2-furoate, and furfural, amongst others, were identified as polysaccharide derivatives from cellulose and hemicellulose depolymerization. This study evidences the need for adequate management of the condensable by-products of charcoal production, both for economic reasons and for controlling their potential environmental impact.

Determining Organic Pollutants in Automotive Industry Sludge

In Brazil, the policy for disposing industrial sludge is changing from an emphasis on using controlled landfills to other treatment or co-processing methods; however, the monitoring of organic pollutants is not mandatory. The present study evaluated two general screening methods for organic pollutants in sludge generated in an automotive industrial complex in southern Brazil. The screening was performed using Soxhlet and sonication extractions and Gas Chromatograph coupled with Quadrupole Mass Spectrometry (GC/qMS). It was concluded that both techniques were effective and that most of the compounds identified were alkanes, phenols and esters. Important pollutants were detected in the sludge, which confirms the necessity of monitoring this type of residue.

USO DA CROMATOGRAFIA GASOSA BIDIMENSIONAL ABRANGENTE (GC×GC) NA CARACTERIZAÇÃO DE MISTURAS BIODIESEL/DIESEL: APLICAÇÃO AO BIODIESEL DE SEBO BOVINO

The growth of biodiesel market and the implementation of regulations related to biodiesel production and biodiesel/diesel blending has encouraged the development of appropriate analytical methods to control the composition of this type of mixture. In this study, an evaluation of the potential of GC×GC for the characterization of samples of beef tallow biodiesel and the composition of blends of biodiesel/diesel is presented. The methodology was applied to beef tallow biodiesel and its mixtures with petrodiesel, ranging from B2 to B50. Results allowed not only the identification and quantification of the biodiesel esters, but also the biodiesel percentage in biodiesel/diesel blends.

Caracterização cromatográfica de compostos orgânicos presentes nos resíduos sólidos provenientes de indústria de reciclagem de papel e sua aplicação na produção de briquetes de carvão vegetal

Recycling of paper in industrial scale has become an established practice worldwide. In this work, organic compositions of three different kinds of sludge generated in recycle paper industry were studied, and the incorporation of one of those sludge in briket was also investigated. The characterization of organic compounds in sludge samples and briket was performed using Gas Chromatography coupled with Mass Spectrometry after a Soxhlet extraction. Different chemical classes were identified in each type of sludge, but just the sludge composed by cellulose residue did not presented polyaromatic hydrocarbons. Four formulations of sludge incorporated with charcoal for briket production were evaluated.