LS-SVM: uma nova ferramenta quimiométrica para regressão multivariada. Comparação de modelos de regressão LS-SVM e PLS na quantificação de adulterantes em leite em pó empregando NIR

Least-squares support vector machines (LS-SVM) were used as an alternative multivariate calibration method for the simultaneous quantification of some common adulterants found in powdered milk samples, using near-infrared spectroscopy. Excellent models were built using LS-SVM for determining R², RMSECV and RMSEP values. LS-SVMs show superior performance for quantifying starch, whey and sucrose in powdered milk samples in relation to PLSR. This study shows that it is possible to determine precisely the amount of one and two common adulterants simultaneously in powdered milk samples using LS-SVM and NIR spectra.

Regulador de llum controlat per ordinador

El llum electric és un tipus d’energia amb la que s’il•lumina tot el món i s’utilitza tant per a il•luminar la nit com per a disposar de llum addicional durant el dia. L’energia es pren directament de la xarxa de subministrament elèctric i permet encendre tot tipus de focus i bombetes. Actualment la necessitat de controlar la intensitat lumínica de focus és de gran utilitat i es poden veure exemples en escenaris de teatres, concerts musicals, domòtica bàsica a vivendes, botigues, restaurants, etc. on s’incorporen aparells òptims per aquest control. Aspectes com la programació d’encesa, apagat i intensitat desitjada de focus a una hora convinguda facilita el fet de fer-ho manualment i disposar de més temps propi. L’objectiu principal d’aquest treball és dissenyar i construir un regulador de llum controlat per ordinador capac de regular la intensitat lumínica de 8 focus independentment l’un de l’altre. El control de regulació s’efectua mitjancant un programa informàtic compatible amb ordinadors que incorporin el sistema operatiu Windows i és programable en el temps permetent seleccionar la intensitat desitjada a diferents hores del dia seleccionat. Com a conclusions es pot destacar un estalvi energètic al regular la intensitat dels focus evitant així la permanent connexio a una tensió màxima de 230 VAC i la oportunitat de construir un regulador de llum amb els documents subministrats.

Síntese de poliestireno sulfonado para aplicações no tratamento de água produzido a partir de copos e bandejas descartadas de poliestireno

In the present paper, the use of poly(styrene sulfonate) (PSS), produced from discarded polystyrene materials through heterogeneous and homogeneous processes, was investigated. The use of PSS for water treatment, using a kaolin suspension as wastewater model, reduced water turbidity for all the employed materials when compared to the blank analysis, without PSS. The most efficient polyelectrolyte was PSS cups obtained by homogeneous route. The same behavior was observed for real system. The homogeneous PSS cups showed a balance between a moderate molecular weight and high anionic character that improved flocks formation and water removal turbidity.

Un sistema para la deteccion de antioxidantes volatiles comunmente emitidos desde especias y hierbas medicinales

An apparatus which allows the direct measurement of the antioxidant capacity of volatiles compounds emitted from some herbs and culinary spices is described. The device comprises: a sample chamber, a mixing chamber, a pump and, a detection system. Volatiles from Clove (Syzygium aromaticum (L.) Merr. & L.M. Perry) were purged and captured into a DPPH-containing solution and changes in the absorbance were recorded on-line. Linear response was observed when temperature was set between 30-53 ºC; nitrogen flow was 15 mL min-1 during 60 min; DPPH concentration was 20 µmol L-1 and a sample size (powdered Clove) ranged between 200-1000 mg.

Borracha natural e nanocompósitos com argila

The natural rubber is a strategic material which can not be replaced by synthetic rubber in many technological applications. Brazil is a rubber importer, but new techniques of cultivation, breeding and diversification of producing species can reverse this situation. One of the best ways to add value to this commodity is nanotechnology. The production of nanocomposites is already a reality and shows that the sustainable use of this natural resource can lead to new products and boost the national agribusiness setting labor-qualified in the field.

Desempenho físico-químico e mecânico de concreto de cimento Portland com borracha de estireno-butadieno reciclada de pneus

Physicochemical and mechanical techniques were carried out to characterize three concrete tyre-rubber waste dosages such as 5, 10 and 15%, w/w. The elastomeric material was identified as styrene-butadiene rubber (SBR). It was observed that the growing SBR content in the mixture decreased the concrete performance. The best results were presented by 5% w/w tyre-rubber waste concrete sample. This composition was tested at Mourão hydroelectric powerplant spillway as repairing material.

O valor energético dos alimentos: exemplo de uma determinação experimental, usando calorimetria de combustão

The energies involved in the combustion, under atmosphere of oxygen, of breakfast cereals and dehydrate powdered whole milk samples, were determined by combustion calorimetry. This practical work, in the field of human nutrition, involved the characterization of the nutritional composition and the combustion of samples of the two foods that are part of the alimentary diet, namely, at breakfast. The obtained results allowed to assess the energy value printed in the foods labels and discuss the way those values are estimated.

Produção de substratos sers eficientes através da deposição de ouro sobre um molde de microesferas de poliestireno

This work reports on the SERS activity of a nanostructured substrate that was obtained by electrodepositing gold over a template consisting of polystyrene microspheres. This substrate displayed superior SERS performance for the detection of 4-merctaptopyridine as compared to a conventional roughened Au electrode. In order to investigate the substrate capability for the detection at low concentration limits, a series of Rhodamine 6G (1 nM) spectra were registered. Our spectral dynamics data is in agreement with single-molecule behavior, showing that the control over the substrate morphology is crucial to enable the production of highly reproducible and sensitive SERS substrates.

Hiilidioksidin talteenottoon soveltuvan anioninvaihtohartsin valmistus ja karakterisointi

Tämän työn tarkoituksena oli tutkia hiilidioksidin talteenottoon soveltuvan anioninvaihtohartsin valmistusmenetelmiä, kokeilla eri menetelmiä käytännössä ja tutkia sekä itse valmistettujen että valmiina saatujen hartsien adsorptiokykyä ja muita ominaisuuksia. Kemiallinen adsorptio amiiniryhmän omaavien hartsien avulla on yksi tapa sitoa hiilidioksidia ilmasta. Primäärinen amiiniryhmä sitoo hiilidioksidia parhaiten. Primäärisen amiiniryhmän omaava anioninvaihtohartsi voidaan valmistaa pohjapolymeeristä halogeenialkyloimalla ja aminoimalla, aminoalkyloimalla tai suoraan aminoimalla. Aminoalkylointi voidaan suorittaa erilaisilla reagensseilla ja katalyyteillä. Tässä työssä hartseja valmistettiin aminoimalla polymetyyliakrylaattidivinyylibentseenipohjaista polymeeriä etyylidiamiinilla ja propyylidiamiinilla. Lisäksi suoritettiin polystyreeni-divinyylibentseenipohjaisen polymeerin aminoalkylointi bis(ftaali-imidometyyli)eetterin avulla. Reaktio tehtiin kahdella eri katalyytillä; rikkitrioksidilla ja rautakloridilla. Aminoalkylointireaktioissa tarvittava eetteri piti ennen varsinaista reaktiota valmistaa N-hydroksymetyyliftaali-imidistä. Myös tämän reagenssin syntetisointia ftaali-imidistä kokeiltiin. Kaikki synteesit onnistuivat melko hyvin, paitsi aminoalkylointi rautakloridikatalyytillä. Hartsien valmistuksen lisäksi itse valmistettuja primäärisen amiiniryhmän omaavia hartseja sekä erilaisia amiiniryhmiä omaavia valmiita hartseja karakterisoitiin eri tavoin. Erityisesti haluttiin tutkia hiilidioksidin adsorptiokapasiteettia ja hartsien termistä kestävyyttä. Kaikista tutkituista hartseista lähimpänä haluttuja ominaisuuksia olivat kaksi kaupallista primäärisen amiiniryhmän omaavaa PS-DVBpohjaista makrohuokoista hartsia. Rakenteeltaan samanlainen itse valmistettu hartsi (rikkitrioksidikatalyytin läsnä ollessa aminoalkyloitu) oli myös ominaisuuksiltaan lupaava. Valmistusmenetelmää pitää kuitenkin tutkia ja kehittää lisää vielä parempien tulosten aikaansaamiseksi. Myös kaupallinen polyetyleeni-imiinirakenteen omaava silikapohjainen hartsi oli ominaisuuksiltaan hyvä.

Síntese e caracterização de nanocompósitos de poliestireno/hidroxissal lamelar

Polystyrene/layered hydroxide salt (LHS) modified with sodium dodecyl sulfate was synthesized by in situ polymerization. The materials synthesized were characterized by gravimetry, X-ray diffraction (XRD), thermogravimetry analyses (TGA), differential scanning calorimetry (DSC) and the flammability test (FT). XRD demonstrated that synthesized nanocomposites in all compositions studied showed poor global dispersion of LHS in polystyrene. TGA showed a slight decrease in thermal stability. DSC curves showed that the glass transition temperature of polystyrene and nanocomposites were similar. The FT showed that the nanocomposite with low load of LHS exhibited good results.

Equipamento de baixo custo para extração em fase sólida em amostras aquosas de grande volume utilizando pressão positiva de N

Extraction/concentration is a crucial step for the analysis of organic compounds at trace level concentrations and dispersed in complex matrices. Solid-phase extraction (SPE) is one of the techniques used for this purpose. In this work, a low cost apparatus for SPE was developed that uses nitrogen under positive pressure and ensures the maintenance of the sample flow, while also allows the simultaneous extraction of different samples without cross-contamination and sample contact with plastic materials. For the system set up, easily accessible materials were used such as hypodermic needles, stainless steel tubes, rubber stoppers, and 3-way valves from serum delivery apparatus.

Aplicações de enzimas na síntese e na modificação de polímeros

Enzymes are biological catalysts that offer great potential for use in the synthesis and modification of polymers, being more specific and greener than chemical catalysts. In this work, enzymes from the classes of hydrolases (lipase, cutinase and protease) and of oxidoreductases (horseradish peroxidase, manganese peroxidase and laccase) were identified as the main biocatalysts responsible for the synthesis of polymers. Biocatalysis can potentially be part of the life cycle of several polymers, including polyesters, polyurethanes, polycarbonates, polyamides, functionalized polysaccharides and polystyrene, allowing the synthesis of specialty macromolecules for fine applications and with higher added-value than commodity polymers.

Estudo do teste de Scott via técnicas espectroscópicas: um método alternativo para diferenciar cloridrato de cocaína e seus adulterantes

Cocaine is usually seized mixed with a wide variety of adulterants such as benzocaine, lidocaine, caffeine, and procaine. The forensic identification of cocaine in these street drug mixtures is normally performed using colorimetric testing kits, but these tests may suffer from interferences, producing false-positive results. Here, we describe the use of analytical techniques including attenuated total reflection Fourier transform infrared (ATR-FTIR) and ultraviolet-visible (UV-VIS) spectroscopies to distinguish between cocaine and other adulterants (lidocaine, promethazine, powdered milk and yeast) that yield positive results on the Scott test using the thiocyanate cobalt reagent. A further 13 substances were also analyzed using the Scott test.

MONITORAMENTO DE RESÍDUOS DE AGROTÓXICOS DA CLASSE DOS ORGANOFOSFORADOS POR CGDFC EM AMOSTRAS DE LEITE FLUÍDO E EM PÓ

Samples of whole fluid pasteurized, UHT and powdered milk were analyzed for the presence of organophosphorus pesticide residues (OPR) using the QuEChERS method with detection by GC-FPD and confirmation by UPLC-MS/MS. A total of 23% of fluid milk samples and 27% of powdered milk samples contained at least one organophosphorus residue. The OPR found in the samples showed these can reach the milk and remain even after pasteurization, sterilization and drying processes. Some domestic sanitary residues were also present in the powdered milk samples. These residues have no LMR in Brazilian food legislation and are therefore not taken into account in food intake evaluations. There was an unidentified chromatographic peak in 30% of all the liquid and powdered milk samples, indicating the presence of some other contaminant.

DIRECT INFUSION ESI-MS APPLIED IN THE DETECTION OF BYPRODUCTS DUE TO REDUCTIVE DEGRADATION OF ACETAMIPRID BY ZERO-VALENT IRON

This study investigated the reductive degradation of acetamiprid (5 mg L-1) in aqueous medium (at pH 2.0) induced by zero-valent iron (50 mg). The process was monitored using high-performance liquid chromatography (HPLC) to determine the degradation rate as a function of reaction time, and direct infusion electrospray ionization mass spectrometry (DI-ESI-MS) to search for (and potentially characterize) any possible byproducts formed during degradation. The results obtained via HPLC showed that after 60 min, the degradation of the substrate reached nearly 100% in an acidic medium, whereas the mineralization rate (as determined by total organic carbon measurements) was as low as 3%. Data obtained by DI-ESI-MS showed that byproducts were formed mainly by insertions of hydrogen atoms into the nitrile, imine, and pyridine ring moieties, in addition to the observation of chlorine substitution by hydrogen replacement (hydrodechlorination) reactions.