References of "Marlet, Christelle"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailComment les insectes communiquent-ils au sein de l’ «écosystème-cadavre» ? L’écologie chimique des insectes nécrophages et nécrophiles
Dekeirsschieter, Jessica ULg; Verheggen, François ULg; Frederickx, Christine ULg et al

in Faunistic Entomology - Entomologie Faunistique (2012), 65

L’entomologie forensique est une discipline des sciences forensiques qui étudie les insectes et d’autres arthropodes dans un contexte médico-légal. Les insectes nécrophages et nécrophiles, principalement ... [more ▼]

L’entomologie forensique est une discipline des sciences forensiques qui étudie les insectes et d’autres arthropodes dans un contexte médico-légal. Les insectes nécrophages et nécrophiles, principalement des Diptères et des Coléoptères, sont fréquemment retrouvés au sein de l’écosystème-cadavre. Pour ces insectes, le cadavre est une ressource éphémère très riche qu’ils vont coloniser de manière plus ou moins prévisible. L’entomofaune des cadavres seraient attirées par les odeurs cadavériques émises par le corps en décomposition. A l’heure actuelle, la thanatochimie est encore peu étudiée et l’information disponible concernant les COVs émis après la mort est limitée. Grâce à l’utilisation des méthodes de chimie analytique (TDS)GC-MS, GCxGC-TOF-MS), la signature olfactive d’un cadavre peut être étudiée au cours du processus de décomposition. L’ « odeur de la mort » est constituée par un mélange de plus de cent composés organiques volatils qui évoluent au cours de la décomposition. Cependant, les sémiochimiques qui sont réellement attractifs pour les insectes nécrophages et/ou nécrophiles ne sont pas encore clairement identifiés. Les espèces pionnières pourraient être attirées par des COVs cadavériques. Toutefois, les espèces plus tardives pourraient aussi être attirées par d’autres types de sémiochimiques produits par les insectes sarcosaprophages eux-mêmes (par exemple : des asticots, des insectes nécrophages). Plusieurs techniques d’écologie chimique peuvent être utiles en vue d’investiguer le rôle des sémiochimiques cadavériques dans le comportement des insectes sarcosaprophages. Une meilleure compréhension de l’écologie chimique des insectes nécrophages/nécrophiles et la thanatochimie pourraient avoir de nombreuses applications en science forensique et plus particulièrement en entomologie forensique. [less ▲]

Detailed reference viewed: 105 (9 ULg)
Full Text
Peer Reviewed
See detailEvaluation d’une méthode d’échantillonnage passif pour la mesure des monoterpènes dans l’air intérieur
Marlet, Christelle ULg; Lognay, Georges ULg; Plaisance, Hervé et al

in Pollution Atmosphérique (2011), 210

Monoterpenes are compounds naturally emitted by wooden materials. A preliminary study had demonstrated the occurrence of some monoterpenes in the timber frame constructions. Contrary to the active ... [more ▼]

Monoterpenes are compounds naturally emitted by wooden materials. A preliminary study had demonstrated the occurrence of some monoterpenes in the timber frame constructions. Contrary to the active sampling, the passive sampling with Radiello® device simplifies the sampling step that is an interest in indoor environment. However, the knowledge of the sampling rate is necessary for quantification via the passive samplers Radiello®. Radiello® sampler with Tenax TA cartridge was evaluated for the 4-h concentration measurements of nine monoterpenes (α-pinene, β-pinene, d-limonene, Δ3-carene, camphene, carvone, 1,8-cineole, linalool and p-cymene). The performance parameters of the method (calibration curve, trueness, repeatability, blank level, stability of samples) were estimated. The sampling rates were first evaluated under the standard conditions in an exposure chamber. The influences of three environmental factors (temperature (T), relative humidity (RH) and concentration level (C)) on the sampling rates were also evaluated following a full factorial design at two factor levels (low and high). The monoterpenes concentrations in the exposure chamber were followed by an active sampling on tube Tenax TA. For both sampling devices, analyses were realized by TD-GC-MS. The results of this study demonstrated that the Radiello® device is suitable for the measurement of 5 of 9 studied monoterpenes. The sampling rates were defined by an equation including two factors, temperature and relative humidity. Temperature is found to be the most important factor leading to variability of the all monoterpene sampling rates. An equation allowing to estimate the sampling rate was established for every studied compound. Measurements of monoterpenes with the Radiello® device were then carried out on new wooden houses and compared with measurements obtained by active sampling on Tenax TA tubes. [less ▲]

Detailed reference viewed: 73 (16 ULg)
Full Text
Peer Reviewed
See detailLes monoterpènes : sources et implications dans la qualité de l’air intérieur
Marlet, Christelle ULg; Lognay, Georges ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(4), 611-622

Terpenes are recurrent in indoor environments. Their sources, biogenic or anthropological origin, are very varied: plants, wooden building materials, household products and furnishings, paints, air ... [more ▼]

Terpenes are recurrent in indoor environments. Their sources, biogenic or anthropological origin, are very varied: plants, wooden building materials, household products and furnishings, paints, air fresheners, perfumed candles. However, in spite of their natural character, these compounds can have significant effects on occupant’s health. Indeed, some monoterpenes are recognized as irritating or allergenic. Furthermore, they react with the other molecules to form potentially more harmful secondary products such as formaldehyde. Numerous studies demonstrated that reactions between monoterpenes and ozone produced airborne particulate matter as well as secondary pollutants among which formaldehyde, acetaldehyde and acetone. However, few studies were realized in the indoor to demonstrate the terpenes and secondary pollutants evolution. The most frequently used technique for the monoterpenes analysis is the TD-GC-MS. The sampling mode depends on the sample introduction system, either the sampling on sorbent tube, or the sampling in a tank. The attraction for the wooden constructions and ecological materials leads to higher indoor monoterpenes concentrations. Does this occurrence have to arouse our interest? The present article has the objective to review the knowledge relative to terpenes, and more exactly on the monoterpenes sources in indoor and their implication in its quality. [less ▲]

Detailed reference viewed: 56 (15 ULg)
Full Text
Peer Reviewed
See detailComparaison of the flower scents of two Impatiens species
Marlet, Christelle ULg; Lognay, Georges ULg; Jacquemart, Anne-Laure et al

Poster (2010, September 27)

The Giant balsam, Impatiens glandulifera Royle (Balsaminaceae) was introduced in Europe from the Himalayas as a garden ornamental plant in 1839. Due to its great success from nursery gardeners (1), it is ... [more ▼]

The Giant balsam, Impatiens glandulifera Royle (Balsaminaceae) was introduced in Europe from the Himalayas as a garden ornamental plant in 1839. Due to its great success from nursery gardeners (1), it is now considered as one of the 100 worst invasive species in Europe. On the contrary, the native I. noli-tangere L. is considered to be in decline. Both species are annuals that absolutely need reproductive output to maintain or extend their populations. High fecundity has frequently been associated with invasiveness. However, traits controlling the reproductive success like pollinator attractiveness have not yet been assessed. The alien species is profusely visited by bumblebees which constituted the main visitors and efficient pollinators (2-3). The native also presents traits linked to insect attractiveness. Flowers produced similar quantities of nectar with the same sugar concentration and composition than the exotic. Therefore, the native could be considered as valuable source of nectar for pollinators. Despite the fact that nectar reward is likely to influence pollinator attractiveness, I. noli-tangere only occasionally received visits. Indeed, a flower of the native is 40 times less visited than a I. glandulifera flower (3). Differences in visitation rates may be explained by several factors, as floral scents, UV patterns or floral display. In summer 2009, a first comparative study of floral scents between these two species was performed. An active sampling in a small glass chamber able to contain single flower left on the plant had been performed on a sorbent tube with Carbograph and Tenax TA. The volatiles of floral scents had been analysed by thermal desorption coupled to gas chromatography and mass spectrometry (4, 5). The composition of flower scents on the basis of area percent of identified peaks had been compared. Terpenes (d-limonene, α-terpinolene, p-cymene, α and β-terpineol) were emitted by the flowers of both species. Higher monoterpenes proportion in area percent was detected for the native species. Terpenes such as β-myrcene, 1,4-cineole, eucalyptol, carveol were absent in the flower scent of the alien I. glandulifera. However, the alien presented a higher alcane proportion. The implication of terpenes in the attractiveness of bumblebees will be studied. [less ▲]

Detailed reference viewed: 45 (3 ULg)
Full Text
Peer Reviewed
See detailDevelopment and validation by accuracy profile of a method for the analysis of monoterpenes in indoor air by active sampling and thermal desorption-gas chromatography-mass spectrometry
Marlet, Christelle ULg; Lognay, Georges ULg

in Talanta (2010), 82(4), 1230-1239

The technique of thermal desorption (TD)-GC/MS was evaluated for the measurement of monoterpenes in indoor air. The validation strategy was intentionally oriented towards routine use and the reliability ... [more ▼]

The technique of thermal desorption (TD)-GC/MS was evaluated for the measurement of monoterpenes in indoor air. The validation strategy was intentionally oriented towards routine use and the reliability of the method rather than extreme performance. For this reason, validation by accuracy profile was chosen. The accuracy profile procedure, which is based on the concept of total error (bias + standard deviation), guarantees that a known proportion of future results obtained with the method will be within acceptance limits. For all the compounds tested in the present study, α-pinene, α-terpineol, β-pinene, d-limonene, Δ3-carene, camphene, 1,8-cineole, p-cymene, linalool, but not in the case of carvone, the accuracy profile procedure established that at least 95% of the future results obtained would be within the ±15% acceptance limits of the validated method over the whole defined concentration range. Other parameters, such as selectivity, recovery, repeatability, stability of the molecules of interest and the effect of temperature, were also determined. The performance of the described method was finally evaluated by the analysis of indoor air from new timber frame constructions. [less ▲]

Detailed reference viewed: 31 (7 ULg)
Peer Reviewed
See detailHarmonia axyridis (Pallas) secondary metabolites quantification in relation with aposematism : Part I : Harmonine quantification
Fischer, Christophe ULg; Heuskin, Stéphanie ULg; Laurent, Pascal ULg et al

Poster (2010, January)

These last few years, the multicoloured Asian ladybird, Harmonia axyridis Pallas (Insects: Coleoptera: Coccinellidae), an invasive species, has swiftly spread out in Europe. This aposematic and highly ... [more ▼]

These last few years, the multicoloured Asian ladybird, Harmonia axyridis Pallas (Insects: Coleoptera: Coccinellidae), an invasive species, has swiftly spread out in Europe. This aposematic and highly polymorphic insect is problematic in several ways. It seems to outcompete native coccinellid species; they can group on fruits in vineyards and spoil wine when crushed with grapes; they can aggregate by hundreds in houses to winter. This study aims to investigate the relations between the chemical defences of H. axyridis and warning signals expressed by this bug. To achieve this goal, two original quantification methods of H. axyridis secondary metabolites have been undertaken. The first one allows Fast-GC quantifying harmonine, its main defence alkaloid. The other one permits to determine its emission rate of 2-isopropyl-3-methoxypyrazine, a highly odorous compound probably involved in the communication between individuals and in the aposematism of this insect. This last point will be detailed in another poster. Firstly, a method of extraction, acetylation and purification of harmonine from H. axyridis has been devised to obtain a calibration standard because this molecule is not commercially available. The identity of the extracted compound has been confirmed by mass spectrometry and multidimensional NMR. The GC purity of this N,N-diacetylharmonine is of 100%. During the experiments, its stability in acetone solution at 4°C has been verified. Using this purified molecule, an original method of harmonine quantification has been developed by fast gas chromatography and validated using accuracy profile. The method has been validated for concentrations ranging from 28µg/ml to more than 264µg/ml, with a maximal error risk of 20%. From about 100µg/ml, peaks symmetry decreased, but did not influence the quantification. That accuracy profile validation has been compared with a more classical validation using AOAC (2006) norm, which confirmed the first validation. This method allows quantifying harmonine in one single insect. Harmonine has been quantified in 80 H. axyridis divided into four groups of at least 15 individuals on basis of the morph type and the elytra hue. Males and females harmonine contents did not significantly differ. The mean harmonine content was of 106.6µg/individual with a standard deviation of 80.2µg/individual. The results distribution obtained was not normal and a strong variability between individuals was observed, which explains the high standard deviation. These results and those of the pyrazine and colour analysis have been statistically analyzed in order to show potential correlations between these factors. It would appear that elytra colour is linked with the insect harmonine content. Individuals with a non-melanic orange colour presented harmonine content significantly higher than other studied colours. The harmonine content does not seem linked to the pyrazine emission rate. [less ▲]

Detailed reference viewed: 192 (24 ULg)
Peer Reviewed
See detailHarmonia axyridis (Pallas) secondary metabolites quantification in relation with aposematism : Part II : Pyrazine quantification
Fischer, Christophe ULg; Heuskin, Stéphanie ULg; Marlet, Christelle ULg et al

Poster (2010, January)

The main objective of this study is to investigate the presence of links between chemical defences and warning signals presented by Harmonia axyridis (Pallas), the multicoloured Asian ladybird (Insects ... [more ▼]

The main objective of this study is to investigate the presence of links between chemical defences and warning signals presented by Harmonia axyridis (Pallas), the multicoloured Asian ladybird (Insects: Coleoptera: Coccinellidae). This second part describes an original quantification method for 2-isopropyl-3-methoxypyrazine (IPMP) by active sampling on thermally desorbed adsorbent (TD) coupled with GC-MS analysis. This highly odorous compound is supposed to be implicated in intra- and interspecific communication. In order to allow harmonine quantification (a defence alkaloid, see Part 1), this method avoid any hemolymph loses by the ladybird (Coccinellids can emit hemolymph when stressed). This method is non-lethal and applicable on one single insect. The quantification method has been validated from 37,5pg to 10 000 pg per adsorbent cartridge. On this range, there is no breakthrough and desorption is complete (>99.4%). At the LOQ (37.5pg/cartridge), the bias is of 20%, but rapidly decreased to less than 5% on the rest of the validated range (100 to 10 000 pg/cartridge). According to AOAC (2006) norm, this method is repeatable but not reproducible. The IPMP emission rate following a stress has been quantified on 80 H. axyridis grouped in four classes on basis of the morph type and the elytra hue. Males and females emission rates did not significantly differ. The mean emission rate is of 707 pg/4h with an extremely high standard deviation of 1766pg/4h due to a great individual variability and a strongly asymmetric distribution of the results. These results and those of the harmonine and colour analysis have been statistically analyzed in order to show potential correlations between these factors. It seems that elytra colour is linked with the insect IPMP emission rate. Individuals with a melanic red colour presented IPMP emission rate significantly lower than other studied colours. The harmonine content does not seem linked to the pyrazine emission rate. [less ▲]

Detailed reference viewed: 118 (7 ULg)
Full Text
See detailAnalysis of aldehydes relaesed by rice flour using sorbent adsorption and thermal desorption - gas chromatography/mass spectrometry: Development and validation
Mertens, Cécile ULg; Marlet, Christelle ULg; Blecker, Christophe ULg et al

Poster (2010, January)

Odor is an essential characteristic and a quality marker in baby foodstuff, like a partially hydrolyzed and pregelatinized rice flour. The rice flour study by active sampling and TD-GC/MS highlighted the ... [more ▼]

Odor is an essential characteristic and a quality marker in baby foodstuff, like a partially hydrolyzed and pregelatinized rice flour. The rice flour study by active sampling and TD-GC/MS highlighted the presence of three aldehydes: Hexanal, Octanal, Nonanal. These compounds are known to be caused by lipid oxidation, one of the major alteration reactions in food. The Method was developed and valited on a large range for the three aldehydes. It was then applied to the rice fllour to determine if it can be used to follow the effect of ageing on the aldehydes production. [less ▲]

Detailed reference viewed: 56 (17 ULg)
Full Text
See detailLow detection HPLC – DAD analysis of aldehydes and ketones in indoor air : Development and validation by accuracy profile
Marlet, Christelle ULg; Haesen, Charlotte ULg; Lognay, Georges ULg

Poster (2010, January)

Aliphatic aldehydes and ketones like formaldehyde are reactive volatile compounds and common indoor pollutants. The main sources are tobacco smoke, combustion gases, painting and materials. Theses ... [more ▼]

Aliphatic aldehydes and ketones like formaldehyde are reactive volatile compounds and common indoor pollutants. The main sources are tobacco smoke, combustion gases, painting and materials. Theses compounds also arise from the reaction between unsaturated compounds and oxidative agents. The toxic potential of formaldehyde and other aliphatic/aromatic carbonyl compounds requires the determination of even low amounts of these compounds in indoor air. The present method for indoor monitoring uses adsorption at 2,4-dinitrophenylhydrazine (DNPH)-coated sorbents followed by HPLC-UV/DAD analysis of the extract. Detection limits of 0.1μg/m3 were reached by this method which is sufficient for indoor air monitoring. Three DNPH-derivatives could be separated well on a RP-Amide column followed by UV/DAD-detection at 360 nm. Recovery rates of 70-100 % were determined using liquid spiking method. Validation strategy was intentionally oriented towards the ease of use in routine and the liability of the method rather than extreme performances. For that, the validation by accuracy profile was chosen. The accuracy profile, based on the concept of total error (bias + standard deviation), allows to correctly conclude about the validity of a procedure and thus, guarantees that a known proportion of future results obtained with the method will be included within acceptance limits. For the three tested compounds, formaldehyde, acetaldehyde and acetone, the accuracy profile gave the guarantee that at least 95% of the future results obtained with the validated method will be within the ±25% acceptance limits over the whole concentration range defined. The HPLC parameters were also determinated. The performance of the method was finally evaluated by the analysis of indoor air from new timber frame construction. [less ▲]

Detailed reference viewed: 140 (10 ULg)