Measuring air pressure with a polymeric gas sensor

In this communication we describe the application of a conductive polymer gas sensor as an air pressure sensor. The device consists of a thin doped poly(4'-hexyloxy-2,5-biphenylene ethylene) (PHBPE) film deposited on an interdigitated metallic electrode. The sensor is cheap, easy to fabricate, lasts for several months, and is suitable for measuring air pressures in the range between 100 and 700 mmHg.

Utilização do sensor linear de luz ILX554 em espectroscopia óptica

This technical note describes the construction of a low-cost optical detector. This device is composed by a high-sensitive linear light sensor (model ILX554) and a microcontroller. The performance of the detector was demonstrated by the detection of emission and Raman spectra of the several atomic systems and the results reproduce those found in the literature.

Development of an optical redox chemical sensor for nitrite determination

An optical chemical sensor for the determination of nitrite based on incorporating methyltrioctylammonium chloride as an anionic exchanger on the triacetylcellulose polymer has been reported. The response of the sensor is based on the redox reaction between nitrite in aqueous solution and iodide adsorbed on sensing membrane using anion exchange phenomena. The sensing membrane reversibly responses to nitrite ion over the range of 6.52×10-6 - 8.70×10-5 mol L-1 with a detection limit of 6.05×10-7 mol L-1 (0.03 µg mL-1) and response time of 6 min. The relative standard deviation for eight replicate measurements of 8.70×10-6 and 4.34×10-5 mol L-1 of nitrite was 4.4 and 2.5 %, respectively. The sensor was successfully applied for determination of nitrite in food, saliva and water samples.

Controle da qualidade na determinação potenciométrica de sulfetos volatilizáveis por acidificação (SVA) utilizando adições de padrão

This paper presents a quality assurance and quality control protocol in order to ensure the reliability of analytical results for the determination of acid volatile sulfides in environmental samples by potentiometry. The monitoring of the ion selective sensor readings must be realized continually and particularly in this situation where the analyte is susceptible to transformation and volatilization. Potentiometry with the standard addition was presented as a rapid, accurate, precise, feasible as well as a low cost technique. Concentrations of the analyte in the range of 0.49 to 1.02 mg L-1 were tested with percentage recoveries varying from 89 to 113%.

Monitoring of praseodymium(III) ions in aqueous solutions, soil and sediment samples by a PVC membrane sensor based on a furan-triazole derivative

A furan-triazole derivative has been explored as an ionophore for preparation of a highly selective Pr(III) membrane sensor. The proposed sensor exhibits a Nernstian response for Pr(III) activity over a wide concentration range with a detection limit of 5.2×10-8 M. Its response is independent of pH of the solution in the range 3.0-8.8 and offers the advantages of fast response time. To investigate the analytical applicability of the sensor, it was applied successfully as an indicator electrode in potentiometric titration of Pr(III) solution and also in the direct and indirect determination of trace Pr(III) ions in some samples.

Uso da RMN como um sensor online em processos industriais

Nuclear magnetic resonance (NMR) is one of the most versatile analytical techniques for chemical, biochemical and medical applications. Despite this great success, NMR is seldom used as a tool in industrial applications. The first application of NMR in flowing samples was published in 1951. However, only in the last ten years Flow NMR has gained momentum and new and potential applications have been proposed. In this review we present the historical evolution of flow or online NMR spectroscopy and imaging, and current developments for use in the automation of industrial processes.

Development of a simple analytical method for determining trihalomethanes in beer using a headspace solid-phase microextraction technique

We developed a simple, rapid, and solventless method for analyzing trihalomethanes in beer samples using headspace solid-phase microextraction. The effects of varying experimental parameters, such as extraction temperature and time, addition of sodium chloride, and agitation speed, on extraction yield were studied using a univariate experimental design. Limits of detection between 0.22 and 0.46 µg L- 1 and wide linear ranges were achieved for trihalomethanes. We measured the trihalomethane recoveries and precision (as the standard deviation of repeat measurements) and demonstrated the applicability of the proposed method by analyzing 32 beer samples.

Optimization of solvent mixtures for extraction from bark of Schinus terebinthifolius by a statistical mixture-design technique and development of a UV-Vis spectrophotometric method for analysis of total polyphenols in the extract

A statistical mixture-design technique was used to study the effects of different solvents and their mixtures on the yield, total polyphenol content, and antioxidant capacity of the crude extracts from the bark of Schinus terebinthifolius Raddi (Anacardiaceae). The experimental results and their response-surface models showed that ternary mixtures with equal portions of all the three solvents (water, ethanol and acetone) were better than the binary mixtures in generating crude extracts with the highest yield (22.04 ± 0.48%), total polyphenol content (29.39 ± 0.39%), and antioxidant capacity (6.38 ± 0.21). An analytical method was developed and validated for the determination of total polyphenols in the extracts. Optimal conditions for the various parameters in this analytical method, namely, the time for the chromophoric reaction to stabilize, wavelength of the absorption maxima to be monitored, the reference standard and the concentration of sodium carbonate were determined to be 5 min, 780 nm, pyrogallol, and 14.06% w v-1, respectively. UV-Vis spectrophotometric monitoring of the reaction under these conditions proved the method to be linear, specific, precise, accurate, reproducible, robust, and easy to perform.

O USO DE UM SENSOR DE LUZ LINEAR COMO RECURSO DIDÁTICO PARA DEMONSTRAR PRINCÍPIOS DE DIFRAÇÃO E ESPECTROSCOPIA

This article presents a discussion on light diffraction by slits and grids as well as the development of an experimental apparatus which provides quantitative observation of the phenomenon. We conducted a brief historical survey on the evolution of the wave theory of light and the role of diffraction in the context of optical spectroscopy. We also reviewed the use of Huygens’ principle to calculate the intensity pattern obtained when light is diffracted by slits and compared the predictions with experimental results obtained using the apparatus developed. Finally, the use of the apparatus in an optical spectroscopy experiment was demonstrated.

Detection of Rhynchosporium secalis in barley seeds from Argentina through polymerase chain reaction technique

Leaf scald of barley caused by Rhynchosporium secalis is an important disease in Argentina. The fungus is a necrotrophic pathogen which survives in stubble, seeds and weeds. Isolation of R. secalis from seeds on artificial media usually has not been successful due to the slow growth rate of the pathogen and strong inhibition by contaminants. The objective in this work was to detect R. secalis in different genotypes of barley seeds in Argentina using the polymerase chain reaction (PCR)-based diagnostic assay. Four barley genotypes were tested in 2004: Quilmes Ayelén, Quilmes Alfa, Barke and Maltería Pampa 1004. The previously described RS8 and RS9 primers were used for the detection of R. secalis in barley seeds. A 264-bp single band was obtained for each cultivar showing the presence of R. secalis. The use of specific primers was efficient in the detection of R. secalis in barley seeds in Argentina and could be used for routine diagnosis, epidemiology and seed transmission studies. This is the first report on the detection of R. secalis in barley seeds in Argentina.

Dióxido de chumbo eletrodepositado sobre grafite como sensor potenciométrico à ions chumbo e sulfato

No presente trabalho, foi desenvolvido um eletrodo de PbO2 eletrodepositado sobre grafite a partir do eletrólito metanosulfonato de chumbo-ácido metanosulfônico contendo o agente tensoativo brometo de cetiltrimetilamônio (BCTA). Foram avaliadas a resposta potenciométrica do eletrodo de PbO2 como sensor à íons Pb2+ e SO4(2-), em pH e força iônica constante. A aplicação deste eletrodo em titulações potenciométricas de precipitação em meio hidro-etanólico também foi investigada. Os resultados demonstraram que o eletrodo de PbO2 eletrodepositado pode ser utilizado como sensor potenciométrico alternativo à íons Pb(II) apresentando uma linearidade na faixa de concentração de 3,98x10-4 a 3,09x10-2 mol L-1 em meio de íons nitrato com limite de detecção de (4,98 ± 0,11)x10-4 mol L-1. Para íons sulfato o eletrodo de PbO2 não responde diretamente porém, estes íons podem ser dosados indiretamente por titulação potenciométrica com solução padrão de Pb(II), em meio ácido, em uma mistura 1:1 (v/v) de etanol-água, com boa definição dos volumes de equivalência. A repetitividade dos potenciais e dos volumes de equivalência obtidos em amostras de concentração milimolar em sulfato, indicam a viabilidade deste eletrodo na dosagem de íons sulfato.

Kokeellisen moodianalyysin hyödyntäminen sääriluun lujuuden määrittämisessä

Diplomityö tehtiin Lappeenrannan teknillisen yliopiston konetekniikan laitokselle. Diplomityö on osa teknillisen yliopiston biomekaanista tutkimusta, jonka tarkoituksena on mallintaa ihmisen tuki- ja liikuntaelimistön toimintaa. Työssä pyrittiin selvittämään, voitaisiinko sääriluuhun kohdistetun mekaanisen herätteen aiheuttamaa värähtelyvastetta analysoimalla saada tietoa luun ominaistaajuuksista ja lujuudesta. Tietoa voitaisiin käyttää esimerkiksi ostoporoosiriskin arvioinnissa sekä ihmiskehon osien toimintaa kuvaavien simulointimallien verifioinnissa. Mittauslaitteistona käytettiin Brüel & Kjær-moodianalyysilaitteistoa. Laitteistokokonaisuuteen kuuluivat herätevasara, elektromagneettinen täristin, voima-anturi, kaksi kiihtyvyysmitta-anturia sekä PulseLab 2.0 –ohjelmistolla varustettu PC-laitteisto. Tulosten jatkoanalyysi suoritettiin MathWorks yhtiön MatLab v 4.0 -ohjelmistolla. Työssä esitellyn mittaustavan ja -laitteiston todettiin soveltuvan sääriluun värähtelyvasteen mittaamiseen. Mittaustulokset eri mittauskertojen välillä samalla henkilöllä ovat yhtenevät. Tutkimuksen tulosten perusteella ei voida osoittaa luun värähtelyvasteen ja lujuuden välistä suoraa korrelaatiota.