Desenvolvimento de um detector piezelétrico para cromatógrafo a gás interfaceado a microcomputador

A piezoelectric detector based on a commercial quartz crystal of 3.57MHz is shown. A PTFE cell attached to the GC-column outlet holds the polymer-coated crystal, whose terminals were removed. Two TTL oscillators (reference and sensor) are used and the beating of their frequencies is monitored through a home-made counter card inserted in a microcomputer. The original thermal conductivity detector was also interfaced, but through a 12-bit analog-to-digital converter. In spite of the well-known fact that QCM has low sensitivity at high temperatures, results show significant peak deformation for low temperatures. In addition, the phenomenon is also dependent on the chemical composition of the absorbent film besides instantaneous partial pressure and chemical composition of the analyte.

Determinação de pesticidas organofosforados em água usando microextração em fase sólida e CGAR-EM

Solid-phase microextraction (SPME) has been applied to direct extraction of 11 organophosphorus pesticides in water using a 100 mm fiber polydimethylsiloxane. The method was evaluated with respect time of exposure, detection limits (LODs), linearity and precision. The detection limits (S/N = 3) depend of each pesticide and varie about ng/L levels. The linearity was satisfactory with coefficients of correlation usually greater than 0.993. The precision of the method was determined by extraction from 4.0 mg/L aqueous standard with coefficients of variation between 5.7 to 17.2%.

Metodologias gerais empregadas no isolamento e identificação estrutural de feromônios de insetos

A selection of common procedures which are used for the identification and analysis of volatile biologically active compounds from insects are described.

Recerca avaluativa sobre el programa “LÍMITS”

Des de la comunitat científica s’ha posat de manifest la necessitat d’avaluar els programes d’intervenció per a la millora de la parentalitat, especialment en el context de la infància i adolescència en risc. En aquesta recerca es presenten els resultats de l’avaluació del programa Límits aportant evidències d’eficàcia i efectivitat, que permeten identificar i descriure les seves fortaleses, així com també aquells elements que poden ser objecte de millora. El programa Límits és una proposta estructurada d’intervenció preventiva de caire selectiu amb grups de famílies de joves d’entre 14 i 18 anys que passen pel circuit de la justícia juvenil. El programa ha estat funcionant des del 2007, en diverses edicions, a tot el territori català aplegant una experiència i trajectòria remarcable que ha incidit en 351 persones i 245 famílies. El programa consta de vuit sessions en grup d’entre dotze i quinze participants, dinamitzat per dos monitors, en les que es treballen diferents estratègies a partir de l’abordatge de continguts relacionats amb les relacions i els lligams, la comunicació, els conflictes, l’establiment de normes i la disciplina. Per dur a terme l’avaluació del programa Límits s’ha partit d’un disseny quasi-experimental, pretest–postest aplicat a un grup programa (GP) i a grup col·laborador (GC) i de manera diferida (dos mesos després de la seva finalització) només al GP per constatar si s’han assolit els resultats previstos. Quan s’analitza l’evolució del GP s’observen millores en les habilitats d’autocontrol de les emocions, el reforç positiu i les relacions familiars. Tanmateix, des del punt de vista de les famílies no s’han observat canvis significatius en la millora de la percepció d’auto eficàcia del rol parental respecte el GC abans i després del programa. La percepció majoritària és que els objectius que planteja el programa són excessivament ambiciosos i en conseqüència, difícilment assolibles. Els responsables consideren que, en alguns casos, el perfil de famílies derivades al programa no és el més adequat perquè presenten problemàtiques molt més agudes a les desitjables per aquest tipus d’intervenció. Com a punts forts, es destaca que el programa és útil als ulls dels responsables i tècnics perquè genera una presa de consciència del problema i de la necessitat de canvi per part de les famílies. Els participants diuen transferir a la vida real algunes habilitats apreses especialment la comunicació i millora de les relacions familiars. Els tècnics aplicadors coincideixen amb la percepció de les famílies tot i declarar percentatges lleugerament inferiors. També és vist com un complement professional a la seva tasca que ajuda a fer un millor seguiment dels casos, i permet seguir treballant amb posterioritat amb les famílies.

Investigación evaluativa sobre el programa "LÍMITES"

Desde la comunidad científica se ha puesto de manifiesto la necesidad de evaluar los programas de intervención para la mejora de la parentalidad, especialmente en el contexto de la infancia y la adolescencia en riesgo. En esta investigación se presentan los resultados de la evaluación del programa Límites aportando evidencias de eficacia y efectividad, que permiten identificar y describir sus fortalezas, así como también aquellos elementos que pueden ser objeto de mejora. El programa Límites es una propuesta estructurada de intervención preventiva de carácter selectivo, con grupos de familias de jóvenes de entre 14 y 18 años que pasan por el circuito de la justicia juvenil. El programa ha estado funcionando desde 2007 en todo el territorio catalán, y ha incidido en un total de 351 personas y 245 familias. El programa consta de ocho sesiones en grupo en las que se trabajan contenidos relacionados con las relaciones y los vínculos, la comunicación, los conflictos, el establecimiento de normas y la disciplina. Para llevar a cabo la evaluación del programa Límites se ha partido de un diseño cuasi-experimental, pretest-postest aplicado a un grupo programa (GP) y grupo colaborador (GC) y de manera diferida (dos meses después de su finalización) sólo en el GP, para constatar si se han alcanzado los resultados previstos. Cuando se analiza la evolución del GP se observan mejoras en las habilidades de autocontrol de las emociones, el refuerzo positivo y las relaciones familiares. Sin embargo, desde el punto de vista de las familias no se han observado cambios significativos en la mejora de la percepción de auto eficacia del rol parental respecto al GC antes y después del programa. La percepción mayoritaria es que los objetivos que plantea el programa son excesivamente ambiciosos y en consecuencia, difícilmente alcanzables. Los responsables consideran que, en algunos casos, el perfil de familias derivadas al programa no es el más adecuado puesto que presenten problemáticas mucho más agudas a las deseables para este tipo de intervención. Como puntos fuertes, se destaca que el programa es útil a los ojos de los responsables y técnicos porque genera una toma de conciencia del problema y de la necesidad de cambio por parte de las familias. Los participantes dicen transferir a la vida real algunas habilidades aprendidas, especialmente la comunicación y mejora de las relaciones familiares. Los técnicos aplicadores coinciden con la percepción de las familias, a pesar de declarar porcentajes ligeramente inferiores. También es visto como un complemento profesional a su tarea que ayuda a hacer un mejor seguimiento de los casos, y permite seguir trabajando con posterioridad con las familias.

Extração e pré-concentração de compostos orgânicos voláteis por permeação em membrana para análise cromatográfica

This work discusses sample preparation processes for gas chromatography (GC) based on the technique of extraction through membrane permeation (MPE). The MPE technique may be easily coupled to GC via a relatively simple device, which is a module that holds the membrane and is directly connected to the GC column. The possibility of operational errors due to sample handling is substantially reduced in an MPE-GC system because the sample preparation and the chemical analysis are accomplished as a one-step process. The MPE technique is of relatively wide application as it can be used for aqueous samples, solid samples and gaseous samples. Depending on the type of sample the extraction is performed with the membrane in direct contact with the sample or in contact with its headspace. The MPE-GC technique is very useful in trace analysis, due to the time-dependent enrichment of the analyte. A typical application of MPE-GC is the analysis of VOCs present in water that may be accomplished with detection limits at the low ppb (mugL-1) level.

Produtos naturais das esponjas marinhas Aaptos sp., Hymeniacidon aff. heliophila, e do nudibrânquio Doris aff. verrucosa

Herein we describe the isolation of homarine and piridiniumbetaine B from the sponge Aaptos sp. Although homarine has a common occurrence among animals, piridiniumbetaine B was only recently isolated from the marine sponge Agelas dispar. The isolation of piridiniumbetaine B from two taxonomically distant marine sponges corroborate previous assumptions that such betaines should be regarded rather as primary metabolites. We have also isolated (9-[5'-(methylthio)-beta-D-xylofuranosyl]adenine (xylosyl-MTA) from the mantle of a nudibranch identified as Doris aff. verrucosa. The occurrence of xylosyl-MTA in the mantle of this animal strongly suggests that it is the same nudibranch species described for the Mediterranean sea. We have been unable to detect any other compound in the mantle extract of D. aff. verrucosa other than xylosil-MTA and sterols. GC-MS analysis of the sterol fraction from the nudibranch and its prey, the sponge Hymeniacidon aff. heliophila, revealed the occurrence of the ubiquitous sterols, cholesterol, brassicasterol, cholestanol, 24-methylcholesterol and 24-ethylcholesterol, as the only common metabolites, therefore precluding any assumption concerning the sequestration of secondary metabolites by the nudibranch from H. aff. heliophila.

Distribuição de coprostanol (5beta(H)-colestan-3beta-ol) em sedimentos superficiais da Baía de Guanabara: indicador da poluição recente por esgotos domésticos

A critical evaluation is presented on the use of faecal sterols for the identification of sewage contamination in Guanabara Bay. Sediments were collected from 8 stations in the bay selected as representative of different contamination levels. GC/MS determination of faecal sterols gave: coprostanol, 335 - 40000 ng g-1; coprostanone, 112-4136 ng g-1; cholesterol, 1407-7800 ng g-1; cholestanol, 2011 - 10900 ng g-1 and cholestanone, 655-7954 ng g-1. The observed concentration is in accordance with the presence of known pollution sources, however, concentration ratios of different sterols species produced unclear results evidently influenced by primary production and microbial processes.

Extração em fase sólida (SPE) e micro extração em fase sólida (SPME) de piretróides em água

The pyrethroids bifenthrin, permethrin, cypermethrin and deltamethrin were extracted by solid phase extraction (SPE) and solid phase microextraction (SPME). The analysis were performed on a gas chromatograph with electron capture detection (GC-ECD). Octadecil Silano-C18, Florisil and Silica stationary phases were studied for SPE. Better results were obtained for Florisil which gave recoveries from 80% to 108%. Pyrethroids extraction by SPME showed a linear response and a detection limit of 10 pg ml-1. Although the data showed that the two extraction methods were able to isolate the pesticide residues from water samples, the best results were obtained by using SPME which is more sensitive, faster, cheeper, being a more useful technique for the analysis of pyrethroids in drinking water.

Constituintes químicos de Gustavia augusta L. (Lecythidaceae)

Gustavia augusta is used in the folk medicine against leishmaniosis and showed anti-inflammatory action. The phytochemical studies of the plant stem bark have led to the isolation of (22E)-stigmasta-7,22-dien-3beta-ol, 24alpha(S)-ethyl-5alpha-colesta-7,trans-22-dien-3-one, D-friedoolean-14-en-3beta-ol, D-friedoolean-14-en-3-one and D-friedoolean-14-en-3alpha-ol along with stigmasterol, alpha-amyrin, beta-amyrin, lupeol, 3alpha-hidroxi-lupeol and betulinic acid. The structures of these compounds were identified by IR, GC/MS, ¹H and 13C NMR spectral analysis and comparison with literature data.

Estudo de compostos orgânicos em lixiviado de aterros sanitários por EFS e CG/EM

The main purpose of this work was the qualitative study of organic compounds in landfill leachate. The samples were collected from a sanitary landfill located at Gravataí, a southern Brazilian city, that receive both, industrial and domestic refuse. The samples were submitted to solid phase extraction (SPE) with XAD-4 resin as the stationary phase. The instrumental analysis was performed by Gas Chromatography with a Mass Spectrometry Detector (GC/MSD). The compounds achieved in the SPE extracts were tentatively identified by the GC/MS library. It was found several oxygen and nitrogen compounds like carboxylic acids, ketones, amines and amides. Sulfur compounds and phthalate esters are also identified.

CGAR E CGAR-EM na análise dos constituintes químicos isolados do extrato hexanico de Sebastiania argutidens (Euphorbiaceae)

The fractionation column with SiO2 of the hexane extract of Sebastiania argutidens (Euphorbiaceae) yielded fractions containing hydrocarbons, carboxylic acids, sterols and pentacyclic triterpenes. Besides, one fraction showed the presence of several methyl esters, including four uncommon long chain palmitate esthers as minor components. The characterization of these chemical constituents have been done by High Resolution Gas Chromatography (HRGC) and HRGC coupled to Mass Spectrometry (GC/MS). Campesterol, stigmasterol, b-sitosterol, glutin-5-en-3-ol were identified by HRGC co-injection with standards.

Reciclagem de cobre proveniente de analisador automático de carbono e nitrogênio

Isotopic and elemental analysis of N, C and S in liquid and solid samples has been simplified with the advent of automated systems. The simplest method of automation for this kind of analysis involves an elemental analyzer interfaced directly to the ion source of an IRMS (Isotope Ratio Mass Spectrometry). In the analyzer reduction system, an expressive amount of oxidized copper is generated as solid residue. This material is normally imported and the price is very high. A methodology was proposed for the recovery of metallic copper in order to recycle this reagent in the reduction system of a GC-IRMS, using the hydrogen gas in the vacuum line. Results show that it is possible to obtain a recycle of about 95 % of the initial metallic copper used in the reduction system.

Fractionation of Wood Extracts

The aim of this thesis was to fractionate wood extracts into pure fractions using membrane technology, to observe membrane behaviour in solvents and to study the effect of conditioning on membrane performance. Four different wood extracts were used in the performed filtrations. In the literature part, the focus was on the effect of different solvent properties on polymeric membranes, especially on their retention and flux. Solute properties, such as shape, polarity and charge, were examined. Transport models, membrane stability and ways to improve the stability, when solvents were filtered, were also discussed. The experimental part consisted of a series of filtrations, where the effect of the wood extracts and solvent concentration on solute retention was observed. Polymeric and ceramic membranes were tested under different conditions and the solute analyses were performed with GC and GC-MS. It was discovered that it is possible to fractionate wood extracts using membrane technology to some extent, but more research must be done to understand the mechanisms behind the various interactions between the solvent and the membrane. Conditioning was also considered as an important part of the membrane pre-treatment.

Carbamato de etila em bebidas alcoólicas (cachaça, tiquira, uísque e grapa)

The presence of ethyl carbamate in cachaças, tiquiras, whiskies and grapes was investigated by GC-MS, monitoring the m/z 62 ion. The external standard method was used for quantitation in 188 samples (126 cachaças, 37 tiquiras, 6 grappas and 19 whiskies). The results of the study for cachaça were analysed considering the geographic origin, distillation type (still or column), bottle coloration (amber or transparent) and ageing. The average contents of ethyl carbamate in cachaças and tiquiras were 0.77 and 2.4 mg L-1, respectively. These values were higher than the mean concentration found in grapes (0.045 mg L-1) and whiskies (0.14 mg L-1). On average the cachaças distilled in column tend to present higher values of ethyl carbamate than those from still. In the sampling studied it was not possible to define a correlation between content of ethyl carbamate, bottle coloration and ageing time.