Determination and characterization of quinolones in foodstuffs of animal origin by CE-UV, LC-UV, LC-Fl, LC-MS and LC-MS/MS

In this work methods for the multiresidue determination of the series of quinolones include in the European regulation in food of animal origin are de veloped and validated in line with Commission Decision 2002/657/EC in terms of linearity, decision limit, capability detection, precision and stability. Mult iresidue methods were established to allow the determination of quinolones covered by EU legislation in 2377/90/EC in muscle of chicken, turkey, pig and cow, plasma of cow and pig, liver of pig and milk of cow. First an extraction step was optimized and a SPE step was applied to clean!up and preconcentrate quinolones prior to their separation by CE or LC and determination by CE!UV, LC!UV, LC!Fl, LC!MS with different ion sources (ESI ,ApCI) and different mass analyser (Q, ToF) and LC!E SI!QqQ tandem mass spectrometry. The limits of quantification obtained are always lower than Maxim um Residue Limit (MRL) established by EU for quinolones in animal products and they can be applied to the control of quinolones in foodstuffs of animal origin . Finally the proposed methods were applied to determine quinolones in samples of turkey and pig muscle, pig plasma and milk of cow. Excellent quality parameters and reduced time of analysis were obtained when LC!ESI!MS/MS is used, although the others techniques presented too satisfactory results.

Etude de la composition initiale et du vieillissement des traces digitales: vers le développement d'une méthode de datation?

«Quel est l'âge de cette trace digitale?» Cette question est relativement souvent soulevée au tribunal ou lors d'investigations, lorsque la personne suspectée admet avoir laissé ses empreintes digitales sur une scène de crime mais prétend l'avoir fait à un autre moment que celui du crime et pour une raison innocente. Toutefois, aucune réponse ne peut actuellement être donnée à cette question, puisqu'aucune méthodologie n'est pour l'heure validée et acceptée par l'ensemble de la communauté forensique. Néanmoins, l'inventaire de cas américains conduit dans cette recherche a montré que les experts fournissent tout de même des témoignages au tribunal concernant l'âge de traces digitales, même si ceux-­‐ci sont majoritairement basés sur des paramètres subjectifs et mal documentés. Il a été relativement aisé d'accéder à des cas américains détaillés, ce qui explique le choix de l'exemple. Toutefois, la problématique de la datation des traces digitales est rencontrée dans le monde entier, et le manque de consensus actuel dans les réponses données souligne la nécessité d'effectuer des études sur le sujet. Le but de la présente recherche est donc d'évaluer la possibilité de développer une méthode de datation objective des traces digitales. Comme les questions entourant la mise au point d'une telle procédure ne sont pas nouvelles, différentes tentatives ont déjà été décrites dans la littérature. Cette recherche les a étudiées de manière critique, et souligne que la plupart des méthodologies reportées souffrent de limitations prévenant leur utilisation pratique. Néanmoins, certaines approches basées sur l'évolution dans le temps de composés intrinsèques aux résidus papillaires se sont montrées prometteuses. Ainsi, un recensement détaillé de la littérature a été conduit afin d'identifier les composés présents dans les traces digitales et les techniques analytiques capables de les détecter. Le choix a été fait de se concentrer sur les composés sébacés détectés par chromatographie gazeuse couplée à la spectrométrie de masse (GC/MS) ou par spectroscopie infrarouge à transformée de Fourier. Des analyses GC/MS ont été menées afin de caractériser la variabilité initiale de lipides cibles au sein des traces digitales d'un même donneur (intra-­‐variabilité) et entre les traces digitales de donneurs différents (inter-­‐variabilité). Ainsi, plusieurs molécules ont été identifiées et quantifiées pour la première fois dans les résidus papillaires. De plus, il a été déterminé que l'intra-­‐variabilité des résidus était significativement plus basse que l'inter-­‐variabilité, mais que ces deux types de variabilité pouvaient être réduits en utilisant différents pré-­‐ traitements statistiques s'inspirant du domaine du profilage de produits stupéfiants. Il a également été possible de proposer un modèle objectif de classification des donneurs permettant de les regrouper dans deux classes principales en se basant sur la composition initiale de leurs traces digitales. Ces classes correspondent à ce qui est actuellement appelé de manière relativement subjective des « bons » ou « mauvais » donneurs. Le potentiel d'un tel modèle est élevé dans le domaine de la recherche en traces digitales, puisqu'il permet de sélectionner des donneurs représentatifs selon les composés d'intérêt. En utilisant la GC/MS et la FTIR, une étude détaillée a été conduite sur les effets de différents facteurs d'influence sur la composition initiale et le vieillissement de molécules lipidiques au sein des traces digitales. Il a ainsi été déterminé que des modèles univariés et multivariés pouvaient être construits pour décrire le vieillissement des composés cibles (transformés en paramètres de vieillissement par pré-­‐traitement), mais que certains facteurs d'influence affectaient ces modèles plus sérieusement que d'autres. En effet, le donneur, le substrat et l'application de techniques de révélation semblent empêcher la construction de modèles reproductibles. Les autres facteurs testés (moment de déposition, pression, température et illumination) influencent également les résidus et leur vieillissement, mais des modèles combinant différentes valeurs de ces facteurs ont tout de même prouvé leur robustesse dans des situations bien définies. De plus, des traces digitales-­‐tests ont été analysées par GC/MS afin d'être datées en utilisant certains des modèles construits. Il s'est avéré que des estimations correctes étaient obtenues pour plus de 60 % des traces-­‐tests datées, et jusqu'à 100% lorsque les conditions de stockage étaient connues. Ces résultats sont intéressants mais il est impératif de conduire des recherches supplémentaires afin d'évaluer les possibilités d'application de ces modèles dans des cas réels. Dans une perspective plus fondamentale, une étude pilote a également été effectuée sur l'utilisation de la spectroscopie infrarouge combinée à l'imagerie chimique (FTIR-­‐CI) afin d'obtenir des informations quant à la composition et au vieillissement des traces digitales. Plus précisément, la capacité de cette technique à mettre en évidence le vieillissement et l'effet de certains facteurs d'influence sur de larges zones de traces digitales a été investiguée. Cette information a ensuite été comparée avec celle obtenue par les spectres FTIR simples. Il en a ainsi résulté que la FTIR-­‐CI était un outil puissant, mais que son utilisation dans l'étude des résidus papillaires à des buts forensiques avait des limites. En effet, dans cette recherche, cette technique n'a pas permis d'obtenir des informations supplémentaires par rapport aux spectres FTIR traditionnels et a également montré des désavantages majeurs, à savoir de longs temps d'analyse et de traitement, particulièrement lorsque de larges zones de traces digitales doivent être couvertes. Finalement, les résultats obtenus dans ce travail ont permis la proposition et discussion d'une approche pragmatique afin d'aborder les questions de datation des traces digitales. Cette approche permet ainsi d'identifier quel type d'information le scientifique serait capable d'apporter aux enquêteurs et/ou au tribunal à l'heure actuelle. De plus, le canevas proposé décrit également les différentes étapes itératives de développement qui devraient être suivies par la recherche afin de parvenir à la validation d'une méthodologie de datation des traces digitales objective, dont les capacités et limites sont connues et documentées. -- "How old is this fingermark?" This question is relatively often raised in trials when suspects admit that they have left their fingermarks on a crime scene but allege that the contact occurred at a time different to that of the crime and for legitimate reasons. However, no answer can be given to this question so far, because no fingermark dating methodology has been validated and accepted by the whole forensic community. Nevertheless, the review of past American cases highlighted that experts actually gave/give testimonies in courts about the age of fingermarks, even if mostly based on subjective and badly documented parameters. It was relatively easy to access fully described American cases, thus explaining the origin of the given examples. However, fingermark dating issues are encountered worldwide, and the lack of consensus among the given answers highlights the necessity to conduct research on the subject. The present work thus aims at studying the possibility to develop an objective fingermark dating method. As the questions surrounding the development of dating procedures are not new, different attempts were already described in the literature. This research proposes a critical review of these attempts and highlights that most of the reported methodologies still suffer from limitations preventing their use in actual practice. Nevertheless, some approaches based on the evolution of intrinsic compounds detected in fingermark residue over time appear to be promising. Thus, an exhaustive review of the literature was conducted in order to identify the compounds available in the fingermark residue and the analytical techniques capable of analysing them. It was chosen to concentrate on sebaceous compounds analysed using gas chromatography coupled with mass spectrometry (GC/MS) or Fourier transform infrared spectroscopy (FTIR). GC/MS analyses were conducted in order to characterize the initial variability of target lipids among fresh fingermarks of the same donor (intra-­‐variability) and between fingermarks of different donors (inter-­‐variability). As a result, many molecules were identified and quantified for the first time in fingermark residue. Furthermore, it was determined that the intra-­‐variability of the fingermark residue was significantly lower than the inter-­‐variability, but that it was possible to reduce both kind of variability using different statistical pre-­‐ treatments inspired from the drug profiling area. It was also possible to propose an objective donor classification model allowing the grouping of donors in two main classes based on their initial lipid composition. These classes correspond to what is relatively subjectively called "good" or "bad" donors. The potential of such a model is high for the fingermark research field, as it allows the selection of representative donors based on compounds of interest. Using GC/MS and FTIR, an in-­‐depth study of the effects of different influence factors on the initial composition and aging of target lipid molecules found in fingermark residue was conducted. It was determined that univariate and multivariate models could be build to describe the aging of target compounds (transformed in aging parameters through pre-­‐ processing techniques), but that some influence factors were affecting these models more than others. In fact, the donor, the substrate and the application of enhancement techniques seemed to hinder the construction of reproducible models. The other tested factors (deposition moment, pressure, temperature and illumination) also affected the residue and their aging, but models combining different values of these factors still proved to be robust. Furthermore, test-­‐fingermarks were analysed with GC/MS in order to be dated using some of the generated models. It turned out that correct estimations were obtained for 60% of the dated test-­‐fingermarks and until 100% when the storage conditions were known. These results are interesting but further research should be conducted to evaluate if these models could be used in uncontrolled casework conditions. In a more fundamental perspective, a pilot study was also conducted on the use of infrared spectroscopy combined with chemical imaging in order to gain information about the fingermark composition and aging. More precisely, its ability to highlight influence factors and aging effects over large areas of fingermarks was investigated. This information was then compared with that given by individual FTIR spectra. It was concluded that while FTIR-­‐ CI is a powerful tool, its use to study natural fingermark residue for forensic purposes has to be carefully considered. In fact, in this study, this technique does not yield more information on residue distribution than traditional FTIR spectra and also suffers from major drawbacks, such as long analysis and processing time, particularly when large fingermark areas need to be covered. Finally, the results obtained in this research allowed the proposition and discussion of a formal and pragmatic framework to approach the fingermark dating questions. It allows identifying which type of information the scientist would be able to bring so far to investigators and/or Justice. Furthermore, this proposed framework also describes the different iterative development steps that the research should follow in order to achieve the validation of an objective fingermark dating methodology, whose capacities and limits are well known and properly documented.

Rapid analysis of multiclass antibiotic residues and some of their metabolites in hospital, urban wastewater and river water by ultra-highperformance liquid chromatography coupled to quadrupole-linear ion trap tandem mass spectrometry

The present work describes the development of a fast and robust analytical method for the determination of 53 antibiotic residues, covering various chemical groups and some of their metabolites, in environmental matrices that are considered important sources of antibiotic pollution, namely hospital and urban wastewaters, as well as in river waters. The method is based on automated off-line solid phase extraction (SPE) followed by ultra-high-performance liquid chromatography coupled to quadrupole linear ion trap tandem mass spectrometry (UHPLC–QqLIT). For unequivocal identification and confirmation, and in order to fulfill EU guidelines, two selected reaction monitoring (SRM) transitions per compound are monitored (the most intense one is used for quantification and the second one for confirmation). Quantification of target antibiotics is performed by the internal standard approach, using one isotopically labeled compound for each chemical group, in order to correct matrix effects. The main advantages of the method are automation and speed-up of sample preparation, by the reduction of extraction volumes for all matrices, the fast separation of a wide spectrum of antibiotics by using ultra-high-performance liquid chromatography, its sensitivity (limits of detection in the low ng/L range) and selectivity (due to the use of tandem mass spectrometry) The inclusion of β-lactam antibiotics (penicillins and cephalosporins), which are compounds difficult to analyze in multi-residue methods due to their instability in water matrices, and some antibiotics metabolites are other important benefits of the method developed. As part of the validation procedure, the method developed was applied to the analysis of antibiotics residues in hospital, urban influent and effluent wastewaters as well as in river water samples

Extracellular Subunit Interactions Control Transitions between Functional States of Acid-sensing Ion Channel 1a.

Acid-sensing ion channels (ASICs) are neuronal, voltage-independent Na(+) channels that are transiently activated by extracellular acidification. They are involved in pain sensation, the expression of fear, and in neurodegeneration after ischemic stroke. Our study investigates the role of extracellular subunit interactions in ASIC1a function. We identified two regions involved in critical intersubunit interactions. First, formation of an engineered disulfide bond between the palm and thumb domains leads to partial channel closure. Second, linking Glu-235 of a finger loop to either one of two different residues of the knuckle of a neighboring subunit opens the channel at physiological pH or disrupts its activity. This suggests that one finger-knuckle disulfide bond (E235C/K393C) sets the channel in an open state, whereas the other (E235C/Y389C) switches the channel to a non-conducting state. Voltage-clamp fluorometry experiments indicate that both the finger loop and the knuckle move away from the β-ball residue Trp-233 during acidification and subsequent desensitization. Together, these observations reveal that ASIC1a opening is accompanied by a distance increase between adjacent thumb and palm domains as well as a movement of Glu-235 relative to the knuckle helix. Our study identifies subunit interactions in the extracellular loop and shows that dynamic changes of these interactions are critical for normal ASIC function.

LC-MS method development and comparison of sampling materials for the analysis of organic gunshot residues

This study aimed at comparing the efficiency of various sampling materials for the collection and subsequent analysis of organic gunshot residues (OGSR). To the best of our knowledge, it is the first time that sampling devices were investigated in detail for further quantitation of OGSR by LC-MS. Seven sampling materials, namely two "swab"-type and five "stub"-type collection materials, were tested. The investigation started with the development of a simple and robust LC-MS method able to separate and quantify molecules typically found in gunpowders, such as diphenylamine or ethylcentralite. The evaluation of sampling materials was then systematically carried out by first analysing blank extracts of the materials to check for potential interferences and determining matrix effects. Based on these results, the best four materials, namely cotton buds, polyester swabs, a tape from 3M and PTFE were compared in terms of collection efficiency during shooting experiments using a set of 9 mm Luger ammunition. It was found that the tape was capable of recovering the highest amounts of OGSR. As tape-lifting is the technique currently used in routine for inorganic GSR, OGSR analysis might be implemented without modifying IGSR sampling and analysis procedure.

Fingermark age determinations: legal considerations, review of the literature and practical propositions

The question of the age of fingermarks is often raised in investigations and trials when suspects admit that they have left their fingermarks at a crime scene but allege that the contact occurred at a different time than the crime and for legal reasons. In the first part of this review article, examples from American appellate court cases will be used to demonstrate that there is a lack of consensus among American courts regarding the admissibility and weight of testimony from expert witnesses who provide opinions about the age of fingermarks. Of course, these issues are not only encountered in America but have also been reported elsewhere, for example in Europe. The disparity in the way fingermark dating cases were managed in these examples is probably due to the fact that no methodology has been validated and accepted by the forensic science community so far. The second part of this review article summarizes the studies reported on fingermark dating in the literature and highlights the fact that most proposed methodologies still suffer from limitations preventing their use in practice. Nevertheless, several approaches based on the evolution of aging parameters detected in fingermark residue over time appear to show promise for the fingermark dating field. Based on these approaches, the definition of a formal methodological framework for fingermark dating cases is proposed in order to produce relevant temporal information. This framework identifies which type of information could and should be obtained about fingermark aging and what developments are still required to scientifically address dating issues.

Avaliação de filtros domésticos comerciais para purificação de águas e retenção de contaminantes inorgânicos

Twenty domestic commercial filters, in order to determine the percentual retention of color, turbidity, dry residue, bicarbonates, carbonates, total hardness, nitrogens, iron, chlorides, fluorides, and residual chlorine (parameters of food legislation) and sulphides in thirteen water samples proceeding from springs, wells, rivers, lakes, drinking patterns and standards, before and after purification were evaluated. The results showed that purifiers presented adequate retention for nitrates (74.8 ± 16.2 %) and residual chlorine (74.0 ± 11.2) and medium retention for sulphides (61.7 ± 11.3); while porcelain plus activated carbon filters presented adequate retention for color (90.0 ± 19.7), turbidity (76.4 ± 18.4) and iron (83.5 ± 15.1). Therefore the retention of carbonates, bicarbonates, total hardness, chlorides, dry residue, fluorides, ammonium nitrogens and nitrites was less than 10%, and the values of pH didn't show significant variation, for all the filters studied.

Aeromonas surface glucan attached throught the O-antigen ligase represents a new way to obtain UDP-Glucose

We previously reported that A. hydrophila GalU mutants were still able to produce UDP-glucose introduced as a glucose residue in their lipopolysaccharide core. In this study, we found the unique origin of this UDP-glucose from a branched α-glucan surface polysaccharide. This glucan, surface attached through the O-antigen ligase (WaaL), is common to the mesophilic Aeromonas strains tested. The Aeromonas glucan is produced by the action of the glycogen synthase (GlgA) and the UDP-Glc pyrophosphorylase (GlgC), the latter wrongly indicated as an ADP-Glc pyrophosphorylase in the Aeromonas genomes available. The Aeromonas glycogen synthase is able to react with UDP or ADP-glucose, which is not the case of E. coli glycogen synthase only reacting with ADP-glucose. The Aeromonas surface glucan has a role enhancing biofilm formation. Finally, for the first time to our knowledge, a clear preference on behalf of bacterial survival and pathogenesis is observed when choosing to produce one or other surface saccharide molecules to produce (lipopolysaccharide core or glucan).

Kierrätyspolttoaineen käyttö leijupetikattilan konseptiin

Diplomityö tehtiin Rautjärven kunnassa sijaitsevalle M-real Simpeleen tehtaan voimalaitokselle. Voimalaitoksella on leijupetikattila ja se tuottaa prosessilämmön ja höyryn kartonki- ja paperikoneelle. Vuotuinen energiantuotanto on noin 115 GWh. Diplomityön tavoitteena oli tutkia kierrätyspolttoaineen käyttöä osana voimalaitoksen polttoainekonseptista. Voimalaitoksen biokattila on leijupetikattila, jossa poltetaan tehtaalta tulevaa kuorta ja lietettä sekä tehtaan ulkopuolisia puuperäisiä biopolttoaineita ja turvetta. Yksi työn päätavoitteista oli laatia voimassa olevan ympäristöluvan muutoshakemus, jotta kierrätyspolttoaineen käytölle saataisiin lupa. Suurten polttolaitosten päästöjen tarkkailu- ja raportointivaatimukset ovat uudistuneet viime vuosina paljon. Suurimpia muutosten aiheuttajia ovat Valtioneuvoston asetukset 1017/2002 ja 362/2003. Tässä työssä kuvataan uusien asetusten tuomia vaatimuksia itse kattilalle ja polttoaineen syötölle, jatkuvatoimisille mittalaitteille ja muille suoritettaville mittauksille. Uutena asiana on myös ilmapäästöjen seurantamittaukset ja -tapa, jolla tulokset ilmoitetaan. Mahdollisimman pieniin leijupetikattilamuutoksiin uskotaan pääsevän korvaamalla kierrätyspolttoaine REF1:llä 5 – 10 % turpeesta tai puupolttoaineista.

Experimental Identification of Actinobacillus pleuropneumoniae Strains L20 and JL03 Heptosyltransferases, Evidence for a New Heptosyltransferase Signature Sequence.

We experimentally identified the activities of six predicted heptosyltransferases in Actinobacillus pleuropneumoniae genome serotype 5b strain L20 and serotype 3 strain JL03. The initial identification was based on a bioinformatic analysis of the amino acid similarity between these putative heptosyltrasferases with others of known function from enteric bacteria and Aeromonas. The putative functions of all the Actinobacillus pleuropneumoniae heptosyltrasferases were determined by using surrogate LPS acceptor molecules from well-defined A. hydrophyla AH-3 and A. salmonicida A450 mutants. Our results show that heptosyltransferases APL_0981 and APJL_1001 are responsible for the transfer of the terminal outer core D-glycero-D-manno-heptose (D,D-Hep) residue although they are not currently included in the CAZY glycosyltransferase 9 family. The WahF heptosyltransferase group signature sequence [S(T/S)(GA)XXH] differs from the heptosyltransferases consensus signature sequence [D(TS)(GA)XXH], because of the substitution of D(261) for S(261), being unique.

Statistical Methods for Conservation and Alignment Quality in Proteins

Construction of multiple sequence alignments is a fundamental task in Bioinformatics. Multiple sequence alignments are used as a prerequisite in many Bioinformatics methods, and subsequently the quality of such methods can be critically dependent on the quality of the alignment. However, automatic construction of a multiple sequence alignment for a set of remotely related sequences does not always provide biologically relevant alignments.Therefore, there is a need for an objective approach for evaluating the quality of automatically aligned sequences. The profile hidden Markov model is a powerful approach in comparative genomics. In the profile hidden Markov model, the symbol probabilities are estimated at each conserved alignment position. This can increase the dimension of parameter space and cause an overfitting problem. These two research problems are both related to conservation. We have developed statistical measures for quantifying the conservation of multiple sequence alignments. Two types of methods are considered, those identifying conserved residues in an alignment position, and those calculating positional conservation scores. The positional conservation score was exploited in a statistical prediction model for assessing the quality of multiple sequence alignments. The residue conservation score was used as part of the emission probability estimation method proposed for profile hidden Markov models. The results of the predicted alignment quality score highly correlated with the correct alignment quality scores, indicating that our method is reliable for assessing the quality of any multiple sequence alignment. The comparison of the emission probability estimation method with the maximum likelihood method showed that the number of estimated parameters in the model was dramatically decreased, while the same level of accuracy was maintained. To conclude, we have shown that conservation can be successfully used in the statistical model for alignment quality assessment and in the estimation of emission probabilities in the profile hidden Markov models.

Comparison of three analytical methods for the determination of quinolones in pig muscle samples

This work presents a comparison between three analytical methods developed for the simultaneous determination of eight quinolones regulated by the European Union (marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, difloxacin, sarafloxacin, oxolinic acid and flumequine) in pig muscle, using liquid chromatography with fluorescence detection (LC-FD), liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The procedures involve an extraction of the quinolones from the tissues, a step for clean-up and preconcentration of the analytes by solid-phase extraction and a subsequent liquid chromatographic analysis. The limits of detection of the methods ranged from 0.1 to 2.1 ng g−1 using LC-FD, from 0.3 to 1.8 using LC-MS and from 0.2 to 0.3 using LC-MS/MS, while inter- and intra-day variability was under 15 % in all cases. Most of those data are notably lower than the maximum residue limits established by the European Union for quinolones in pig tissues. The methods have been applied for the determination of quinolones in six different commercial pig muscle samples purchased in different supermarkets located in the city of Granada (south-east Spain).

Particle detector link system modifications in RE1/1 sector

The large hadron collider constructed at the European organization for nuclear research, CERN, is the world’s largest single measuring instrument ever built, and also currently the most powerful particle accelerator that exists. The large hadron collider includes six different experiment stations, one of which is called the compact muon solenoid, or the CMS. The main purpose of the CMS is to track and study residue particles from proton-proton collisions. The primary detectors utilized in the CMS are resistive plate chambers (RPCs). To obtain data from these detectors, a link system has been designed. The main idea of the link system is to receive data from the detector front-end electronics in parallel form, and to transmit it onwards in serial form, via an optical fiber. The system is mostly ready and in place. However, a problem has occurred with innermost RPC detectors, located in sector labeled RE1/1; transmission lines for parallel data suffer from signal integrity issues over long distances. As a solution to this, a new version of the link system has been devised, a one that fits in smaller space and can be located within the CMS, closer to the detectors. This RE1/1 link system has been so far completed only partially, with just the mechanical design and casing being done. In this thesis, link system electronics for RE1/1 sector has been designed, by modifying the existing link system concept to better meet the requirements of the RE1/1 sector. In addition to completion of the prototype of the RE1/1 link system electronics, some testing for the system has also been done, to ensure functionality of the design.

Determinação de carbaril utilizando testes ELISA (Enzyme-linked immunosorbent assay) e CLAE com detecção por arranjo de diodos

ELISAs have been applied to pesticide residue analysis due to their high sensitivity and selectivity. However, some ELISAs performance may be affected by matrix components. In this work, ELISA for carbaryl in water samples was checked for interference by naturally occurring fulvic acids. The results suggested that the high fulvic acid concentration (ž³30 mg L-1) and acidic pH conditions (pH 4.0) interfere with the signal detection decreasing the method sensitivity. A dilution of the samples and adjust to pH 8.0 are appropriate to minimize the matrix interferences in the ELISA method. Good correlation between ELISA and HPLC-DAD results was observed.

Relato de uma experiência: recuperação e cadastramento de resíduos dos laboratórios de graduação do Instituto de Química da Universidade Federal do Rio Grande do Sul

An experience aiming to promote a residue interchange and recovery between the teaching laboratories of the Chemistry Institute of this University is described. At the present, several residues interchange have already appeared as advantageous. To make the work easier, a software has been developed in order to keep a record of all the residues generated by the teaching laboratories. Standard labels have been developed for the residues in order to organize them. The software and the label design are described.