Sterolic composition of Chétoui virgin olive oil: Influence of geographical origin

The sterol profile of Tunisian virgin olive oils produced from Chétoui cultivar, the second main variety cultivated in the north of the country, grown under different environmental conditions, was established by gas chromatography using a flame ionisation detector. More than ten compounds were identified and characterised. As expected for virgin olive oil, the main sterols found in all Chétoui olive oils were β-sitosterol, Δ5-avenasterol, campesterol and stigmasterol. Cholesterol, 24-methylenecholesterol, clerosterol, campestanol, sitostanol, Δ7-stigmastenol, Δ5,24-stigmastadienol, and Δ7-avenasterol were also found in all samples, but in lower amounts. Most of these compounds are significantly affected by the geographical origin. The majority of the Chétoui virgin olive oils analysed respected EC Regulation No. 2568, and in all cases total sterol amounts were higher than the minimum limit set by legislation, ranging from 1017 to 1522 mg/kg.     

Intrinsic biodegradation potential of aromatic hydrocarbons in an alluvial aquifer--potentials and limits of signature metabolite analysis and two stable isotope-based techniques

Three independent techniques were used to assess the biodegradation of monoaromatic hydrocarbons and low-molecular weight polyaromatic hydrocarbons in the alluvial aquifer at the site of a former cokery (Flémalle, Belgium).Firstly, a stable carbon isotope-based field method allowed quantifying biodegradation of monoaromatic compounds in situ and confirmed the degradation of naphthalene. No evidence could be deduced from stable isotope shifts for the intrinsic biodegradation of larger molecules such as methylnaphthalenes or acenaphthene. Secondly, using signature metabolite analysis, various intermediates of the anaerobic degradation of (poly-) aromatic and heterocyclic compounds were identified. The discovery of a novel metabolite of acenaphthene in groundwater samples permitted deeper insights into the anaerobic biodegradation of almost persistent environmental contaminants. A third method, microcosm incubations with ¹³C-labeled compounds under in situ-like conditions, complemented techniques one and two by providing quantitative information on contaminant biodegradation independent of molecule size and sorption properties. Thanks to stable isotope labels, the sensitivity of this method was much higher compared to classical microcosm studies. The ¹³C-microcosm approach allowed the determination of first-order rate constants for ¹³C-labeled benzene, naphthalene, or acenaphthene even in cases when degradation activities were only small. The plausibility of the third method was checked by comparing ¹³C-microcosm-derived rates to field-derived rates of the first approach. Further advantage of the use of ¹³C-labels in microcosms is that novel metabolites can be linked more easily to specific mother compounds even in complex systems. This was achieved using alluvial sediments where ¹³C-acenaphthyl methylsuccinate was identified as transformation product of the anaerobic degradation of acenaphthene.     

Application of solid-phase microextraction to the analysis of volatile compounds in virgin olive oils from five new cultivars

Evaluation and identification of wild olive genetic resources allowed us to select new olive varieties and to recognize Tunisian grove richness and diversity. Five new olive cultivars were previously selected among populations of wild olive plants on the basis of agronomic and chemical evaluations. Their virgin olive oils were analysed for their fatty acid composition, quality indices (Free acidity, PV and UV characteristics) and oxidative stability. They were then submitted to solid phase microextraction (SPME) and their volatile compositions were determined.     

A denuder-filter sampling technique for the detection of gas and particle phase carbonyl compounds

A denuder-filter sampling technique for the simultaneous collection of gas and particle phase carbonyl compounds has been developed and tested. The denuder was coated with XAD-4 resin and the derivatizing agent O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) to enable on-tube conversion of gas-phase carbonyls to their oxime derivatives which were extracted and identified by GC-MS. The performance of the PFBHA-coated denuder was tested on a range of carbonyls, dicarbonyls, aromatic aldehydes, carbonyl-containing furans, and benzoquinones. The collection efficiency of the PFBHA-coated denuder was over 90% for sampling times of 10 min and significantly higher than when using only XAD-4 as the sorbent. The collection efficiency and rate of on-tube derivatization was highest for aldehydes and lowest for ketones, consistent with the expected reactivity of carbonyls with PFBHA. The method was used to separate the gas and particle phase carbonyl products formed during the photooxidation of toluene in order to assess its potential for application to simulation chamber experiments of VOC oxidation. The results indicate that when compared to a conventional filter sampling setup, the PFBHA-coated denuder-filter reduced the extent of gas phase adsorption onto the filter by at least a factor of 2 for each of the carbonyls formed. Further potential applications of the denuder-filter sampling method are discussed.     

Volatile compounds from Chétoui olive oil and variations induced by growing area

Fruits from the same variety of Olea europaea L., grown under different environmental conditions in the north of Tunisia, were harvested at the same ripening degree and immediately processed. The volatile profile of virgin olive oils was established using solid phase, micro-extraction (SPME) and gas chromatography-mass spectrometry (GC-MS). Compounds belonging mainly to the following chemical classes characterised the volatile profiles: esters, aldehydes, ketons, aliphatic alcohols and hydrocarbons. Significant differences in the proportions of volatile constituents from oils of different geographical origins were detected and the major volatile in approximately 50% of the oil samples was the aldehyde (E)-2-hexenal. The results suggest that, beside the genetic factor, environmental conditions influence the volatile formation.     

Field comparison of particulate PAH measurements using a low-flow denuder device and conventional sampling systems

Polyaromatic hydrocarbons (PAHs) are complex carbonaceous compounds emitted to the atmosphere by various combustion processes. Because the toxicity of many of them is now well recognized and documented, the determination of their atmospheric concentrations is of great interest to better understand and develop future atmospheric pollution control strategies. Hence, a common sampling protocol has to be defined to homogenize the results. With this goal in mind, field studies were carried out under different environmental conditions (74 samples) by simultaneously operating both a conventional sampler and a sampler equipped with a denuder tube upstream from the filter. The experimental results presented in this work show that the atmospheric particulate PAH concentrations are underestimated at least by a factor of 2 using a conventional sampler. The discrepancy between the two kinds of samplers used varied a lot from one compound to another and from one field campaign to another. This discrepancy may be explained by a simple degradation of particulate PAH in the natural atmosphere and on the filter. This is particularly worrisome because, based on the results presented in this work, the atmospheric PAH concentrations measured using conventional samplers not equipped with an ozone trap can underestimate the PAH concentration by more than 200%. This is especially true when the samples are collected in the vicinity of the point source of particulate PAHs and for highly reactive compounds such as benzo[a]pyrene.     

Numeris-ISDN in France

The development of Numeris, a nationwide integrated services digital network (ISDN) in France, and the accompanying repertoire of ISDN products is discussed. Numeris was commercially opened in France on December 21, 1987 and was made available nationwide three years later in December 1990. Numeris' growth exploded in 1991, increasing from 25000 sold B-channels at the end of 1990 to 150000 at the end of 1991; the goal is one million for 1995. The ISDN markets are reviewed, and the three needs that Numeris satisfies-application, computer networking, and PABX renewal-are described. A market forecast is presented