ABSTRACT Zinc is an essential micronutrient for plant metabolism and has been studied in several crops of economic interest. However, there is no evidence of its use in coconut crops. The objective of this study was to evaluate the influence of foliar zinc fertilization with doses of zinc on dwarf green coconut seedlings based on their nutritional status, growth attributes, and gas exchange. The experimental design consisted of randomized blocks, and the treatments consisted of different zinc doses (0, 5, 10, 15, 20, and 25 g per plant) with five replicates. Seedlings were positively influenced by zinc dose, mainly in terms of growth variables and gas exchange. Zinc fertilization reduced iron and manganese content and increased zinc concentrations in the leaf tissue. Zinc fertilization promoted an increase in leaf area, height, shoot dry mass, and total dry mass. Furthermore, zinc fertilization improved photosynthesis, transpiration, stomatal conductance, internal CO2 concentration, instantaneous water use efficiency, and intrinsic water use efficiency. The improvement in these growth indices and gas exchange, in most variables, was up to an estimated dose of approximately 16 g of zinc per plant and decreased with increasing doses.

RESUMO O zinco é um micronutriente de importância essencial para o metabolismo vegetal, é estudado para diversas culturas de interesse econômico, porém sem evidências de estudo para a cultura do coqueiro. Objetivou-se com este estudo avaliar a influência da fertilização com doses de zinco via foliar em mudas de coqueiro anão verde, por meio do estado nutricional, atributos de crescimento e trocas gasosas. O delineamento experimental foi em blocos ao acaso, e os tratamentos foram constituídos por doses de zinco (0, 5, 10, 15, 20 e 25 g por planta), com cinco repetições. As mudas foram influenciadas positivamente pelas doses de zinco principalmente nas variáveis de crescimento e nas trocas gasosas. No estado nutricional afetou de maneira decrescente o ferro e o manganês e aumentou o zinco no tecido foliar. O zinco proporcionou incrementos na área foliar, altura de plantas, massa seca da parte aérea e massa seca total. Além disso, melhorou a fotossíntese, transpiração, condutância estomática, concentração interna de CO2, eficiência instantânea do uso da água e eficiência intrínseca do uso da água. A melhora nesses índices de crescimento e trocas gasosas, na maioria das variáveis, foi até a dose estimada de aproximadamente 16 g de zinco por planta e diminuiu com o aumento das doses.

ABSTRACT Objective To verify the presence of variants in HNF1B in a sample of the Brazilian population selected according to the presence of renal cysts associated with hyperglycemia. Subjects and methods We evaluated 28 unrelated patients with clinical suspicion of HNF1B mutation because of the concomitant presence of diabetes mellitus (DM) or prediabetes and renal cysts. Genotyping was accomplished using Sanger sequencing or multiplex ligation-dependent probe amplification (MLPA). In positive cases, available relatives were recruited. Results We found two patients with HNF1B mutations. The first presented the variant p.Pro328Leufs*48(c.983delC) and had DM, renal cysts, and hypomagnesemia. The second presented a heterozygous whole gene deletion in HNF1B, DM, renal cysts, body and tail pancreatic agenesis, and hypomagnesemia; this alteration was also found in his two siblings and his father. Conclusion The recruitment of suspected cases of HNF1B gene mutations in Brazilians due to hyperglycemia and renal cysts presents two positive cases. Our cases contribute to the annotation of clinical and biochemical phenotypes of this rare form of maturity-onset diabetes of the young (MODY).

Natural dyes can be used in dye sensitized solar cells (DSSCs) to generate low-cost devices, although with low light harvesting because of energy losses from the recombination process. This study investigates recombination reactions in DSSCs with natural dyes extracted from eggplants, plums, and hibiscus flowers. Titanium dioxide films were coated on a fluorine-doped tin oxide glass conductor substrate by the doctor blading method and impregnated in a dye solution for 24 h. Electrodeposited platinum was used as the cathode, and I3–/I– as the redox couple. The techniques employed were: intensity modulated photovoltage spectroscopy, intensity modulated photocurrent spectroscopy, electrochemical impedance spectroscopy, charge extraction, and cyclic voltammetry. The results show that cells containing plum dye exhibited the best photovoltaic parameters, with high values of gap, charge extraction, and potential, being less resistive to charge transfer with an electron lifetime of 0.51 s, collection time of 8.54 ms, and charge efficiency collection of 0.99.

Corrosion processes were evaluated for AISI 316 and AISI 1020 steels by scanning electron microscopy (SEM), atomic force microscopy (AFM) and light microscopy. Coupons were immersed in four crude oil samples with different total acid numbers (TANs) for 48 days at room temperature. The steels were also exposed to three blends (B1-B3), produced by quaternary mixtures of the oils, with lower TANs than their respective original oils. SEM micrographs showed pitting-type corrosion in most cases. AFM imaging showed drastic changes in the peak-to-peak values, topographic profiles and phase images of the AISI 1020 coupons exposed to all oils and blend B3 as compared to the unexposed steel. Defects were produced on the surface of almost all the samples exposed to naphthenic corrosion. Exposure to the oil blends reduced the extent of the naphthenic corrosion on the coupons, especially blends B1 and B2. The oil mixtures (blends) reduced corrosion.

RESUMO: Muitas espécies de animais silvestres de vida livre servem como reservatório de bactérias patogênicas que ameaçam a saúde humana e dos animais domésticos. Algumas bactérias, como Campylobacter jejuni, Campylobacter coli, Yersinia enterocolitica e Salmonella enterica, causam enfermidades em humanos e podem contaminar os animais domésticos e silvestres. O Núcleo de Reabilitação da Fauna Silvestre da Universidade Federal de Pelotas (NURFS-UFPel) soluciona uma demanda regional específica de atenção à fauna silvestre brasileira. O objetivo desse trabalho foi identificar a presença de Campylobacter jejuni, Campylobacter coli, Salmonella spp. e Yersinia enterocolitica em animais silvestres que se encontravam em processo de reabilitação. Foram coletadas amostras de fezes, com uso de zaragatoas estéreis, de 34 aves, 16 mamíferos e 23 répteis. Dos 73 animais amostrados, quatro (5,48%) albergavam Y. enterocolitica, sendo duas aves, um mamífero e um réptil. Salmonella e Campylobacter não foram isolados. Os perfis de bandas dos isolados de Y. enterocolitica analisados pela rep-PCR foram diferentes entre si. Esses resultados indicam que as cepas isoladas não estão relacionadas entre si, não possuindo uma origem comum recente. Vanellus chilensis, Turdus rufiventris, Didelphis albiventris e Pantherophis guttatus podem albergar Y. enterocolitica e eliminá-la nas fezes, oferecendo risco de disseminação desse micro-organismo no ambiente, além de constituírem possíveis fontes de contaminação para humanos e outros animais.

ABSTRACT: Wild animals can transmit pathogenic bacteria to human and domestic animal’s health. Some bacteria, such as Campylobacter jejuni, Campylobacter coli, Yersinia enterocolitica and Salmonella enterica, cause diseases in humans and can contaminate domestic and wild animais. The Núcleo de Reabilitação da Fauna Silvestre of Universidade Federal de Pelotas (Nurfs-UFPel) attend a specific regional demand of wildlife in Brazil. The aim of this paper was to identify the presence of these pathogenic bacteria in wild animals in rehabilitation. Stool samples were collected using sterile swabs from 34 birds, 16 mammals and 23 reptilian that were housed at Nurfs. Of the 73 collections, Y. enterocolitica was isolated from four (5.48%) of two birds, one mammal and one reptile. Salmonella and Campylobacter were not isolated. The molecular profile of bands of Y. enterocolitica identified in rep-PCR had differences. These results indicated that the isolates did not have a recent common origin. Pantherophis guttatus, Didelphis albiventris, Turdus rufiventris and Vanellus chilensis could shelt Y. enterocolitica and eliminate the bacteria in stool, offering risk of dissemination of these microorganisms in the environment with possible contamination of humans and other animals.

Dye-sensitized solar cells using natural dyes have lower cost when compared to ruthenium-based dyes. This paper aims to evaluate, electrochemically, solar cells composed of TiO2 with dye extracted from the Hibiscus(var. Sabdariffa) and propose an adsorption model capable of predicting the adsorption mechanism of the dye on the semiconductor surface. The characterization techniques used were: Fourier Transform Infrared Spectroscopy, UV-VIS Spectroscopy, Measurement of the Open Circuit Potential, Photocronoamperometry, and Current Density Curves vs. Potential. The infrared spectroscopy confirmed there was adsorption of dye on the TiO2 surface. The adsorption isotherm with the better value of linear coefficient (R= 0.9874) was the Langmuir isotherm. The electrochemical techniques showed that the best cell prepared from a solution with a concentration of 5.27 mg L-1 of the natural dye, had an Eca= 516 mV, j = 0.15 mA cm-2 and an energy efficiency (η) of 0.15%.

Copaiba oil, an oleoresin extracted from Copaifera genus, has been widely used in popular medicine for the treatment of several diseases. The aim of this study was to investigate the antifungal activity of the copaiba oil and its isolated compounds caryophyllene oxide, copalic acid and acetoxycopalic acid against Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum gypseum strains, using microdilution method and microscopy techniques. It was found that the copaiba oil and the copalic acid were active against dermatophytes by minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) tests. The MIC and MFC of copaiba oil against T. rubrum, T. mentagrophytes and M. gypseum were 125 µg mL-1 (250 µg mL-1), 500 µg mL-1 (500 µg mL-1) and 250 µg mL-1 (250 µg mL-1), respectively. For copalic acid, the MIC and MFC were 50 µg mL-1 (100 µg mL-1), 100 µg mL-1 (100 µg mL-1) and 50 µg mL-1 (100 µg mL-1), respectively. Fluorescence microscopy and scanning electronic microscopy were used to investigate inhibition on hyphal growth by compounds, copaiba oil and copalic acid, showing a strong inhibition and an irregular growth pattern. Cell wall, cytoplasmic membrane and intracellular contents were also damaged. In conclusion, copaiba oil and copalic acid showed great activity against dermatophytes, being potential compounds for the development of antifungal drugs.

ABSTRACT One of the reasons for the success of a productive culture is the correct sowing. Therefore, the seeds must be properly dosed, deposited and not damaged by the metering mechanism of the seed drill. So, the aim of this study was to evaluate in a simulator the sorghum seed deposition by a metering mechanism with continuous flow in different conditions of slope and sowing speed, and evaluate the quality of the deposited seeds assessing mechanical damage and germination. The experiment was carried out at the College of Agricultural Sciences, UNESP in Botucatu-SP, being used a simulator equipped with seed metering mechanism of helical channelled rotor type. The experimental design was randomized in a 3 x 2 factorial arrangement with six replications. The factors were three lateral slopes drill, 3%, 8% and 16%, and two sowing speed, 4 and 10 km h-1. For the damage and germination variables we added a control treatment whose seeds were evaluated without being distributed by the metering mechanism. The results indicate that increasing the lateral slope and working speed reduce the rate of seed deposition. The metering mechanism provides mechanical damage and contributes to the reduction of seed germination.

Resumo: A acidificação urinária com cloreto de amônio (CA) é um método preventivo eficiente em urolitíase obstrutiva em ovinos. Os objetivos deste estudo com ovinos confinados, que receberam dieta concentrada com elevado teor proteico, foram: verificar o efeito da dieta sobre a formação de urólitos e o desenvolvimento da doença; analisar as características macroscópicas e histopatológicas do sistema urinário; relacionar os achados clínicos, laboratoriais e necroscópicos com a presença de urólitos. Utilizaram-se 60 ovinos machos: grupo CA (n=40), 400 mg/kg CA/dia, tratados via oral, por 42 dias consecutivos; grupo-controle (n=20), não tratado. Determinaram-se sete momentos de colheita de amostras com intervalos de sete dias, no total de 56 dias de confinamento. Encontraram-se microcálculos na pelve renal em cinco animais de ambos os grupos. As lesões renais microscópicas mais relevantes foram congestão vascular e necrose tubular. Concluiu-se que a dieta rica em concentrado provocou lesão renal em ambos os grupos, embora sem alterar a função renal, o que foi comprovado em testes pela ureia e creatinina séricas. O cloreto de amônio fornecido ao grupo CA não impediu a calculogênese, mas reduziu sua prevalência em relação ao grupo-controle. Os ovinos do grupo-controle tiveram maior comprometimento renal, pela alta incidência de cristalúria e pela necrose tubular, induzidas pelo consumo da dieta rica em grãos.

Abstract: The urinary acidification with ammonium chloride (AC) is an efficient preventive method for urolithiasis in sheep. The objectives of this study with feedlot sheep receiving concentrated diet with high protein content were (1) to verify the effect of diet on urolith formation and development of the disease, (2) to analyze the macroscopic and histopathological characteristics of the urinary system, and (3) to relate the clinical, laboratory and necropsy findings with the presence of uroliths. Sixty male sheep were used: AC group (n=40), 400mg/kg AC/day, orally treated for 42 consecutive days, and control group (n=20), untreated. Seven times were determined for sampling with a seven-day interval, totaling 56 days of feedlot. Small uroliths were found in the renal pelvis of five sheep in both groups. The most relevant microscopic renal lesions were vascular congestion and tubular necrosis. It was concluded that the highly concentrated diet caused renal injury in both groups, without changing the renal function, what was proven by laboratory tests of urea and creatinine. Ammonium chloride provided to the CA group did not prevent urolith formation, but reduced its prevalence in comparison with the control group. Sheep of the control group had increased kidney damage, which resulted in higher incidence of crystalluria and tubular necrosis induced by the consumption of a diet rich in grains.

As técnicas imagiológicas são o método convencional para a avaliação dos processos de cicatrização das fraturas. No entanto, estes métodos não são talvez totalmente confiáveis para a deteção precoce de complicações, as mais frequentes destas sendo o atraso da união e a não-união. Um diagnóstico eficaz destas desordens poderia prevenir a dor e a incapacidade prolongada do paciente. Esforços devem ser dirigidos no sentido do desenvolvimento de novas tecnologias para melhorar a exatidão no diagnóstico de complicações após fraturas ósseas. A variação nos níveis dos marcadores do turnover ósseo (BTMs) têm sido avaliados com vista à sua capacidade para prever o comprometimento da cicatrização das fraturas numa fase inicial, no entanto, as conclusões de alguns estudos não são consensuais. Neste artigo os autores fizeram uma revisão do potencial dos BTMs como fatores de previsibilidade precoce do prognóstico em doentes adultos que apresentavam fraturas ósseas traumáticas mas que não sofriam de osteopenia ou osteoporose pós-menopausa. A informação disponível nos diferentes estudos realizados neste campo foi sistematizada com vista a evidenciar-se os BTMs mais promissores para a avaliação da evolução da cicatrização das fraturas.

Imaging techniques are the standard method for assessment of fracture healing processes. However, these methods are perhaps not entirely reliable for early detection of complications, the most frequent of these being delayed union and non-union. A prompt diagnosis of such disorders could prevent prolonged patient distress and disability. Efforts should be directed towards the development of new technologies for improving accuracy in diagnosing complications following bone fractures. The variation in the levels of bone turnover markers (BTMs) have been assessed with regard to there ability to predict impaired fracture healing at an early stage, nevertheless the conclusions of some studies are not consensual. In this article the authors have revised the potential of BTMs as early predictors of prognosis in adult patients presenting traumatic bone fractures but who did not suffer from osteopenia or postmenopausal osteoporosis. The available information from the different studies performed in this field was systematized in order to highlight the most promising BTMs for the assessment of fracture healing outcome.

CONTEXTUALIZAÇÃO: Atualmente relaciona-se a fraqueza dos músculos do quadril e da coxa ao surgimento da dor anterior no joelho (DAJ). Dessa maneira, compreender como os agachamentos devem ser realizados para melhorar a ativação elétrica desses músculos é importante para o tratamento fisioterapêutico. OBJETIVO: Comparar a ativação mioelétrica de estabilizadores da patela e pelve entre as posições de agachamentos convencional e associado à contração isométrica em adução e abdução da coxa em indivíduos sem queixa de DAJ. MÉTODOS: O sinal eletromiográfico foi captado a partir de eletrodos duplo-diferenciais posicionados nos músculos vasto medial oblíquo (VMO), vasto lateral oblíquo (VLO), vasto lateral longo (VLL) e glúteo médio (GMed) em 15 mulheres sedentárias e clinicamente saudáveis, durante a contração de agachamentos convencional e associados à adução e à abdução isométrica da coxa com carga de 25% do peso corporal. A análise estatística empregada foi o modelo linear de efeitos mistos, com significância de 5%. RESULTADOS: A associação da adução e abdução isométrica da coxa no agachamento produziu cerca de 0,47 (0,2) e 0,59 (0,22), respectivamente, de atividade elétrica do músculo GMed, enquanto o agachamento convencional (AGA) produziu 0,33 (0,27) de atividade elétrica. A maior ativação do VMO aconteceu na contração de agachamento associado à adução da coxa e foi de 0,59 (0,27); já o músculo VLL apresentou uma maior atividade elétrica durante o agachamento associado à abdução, sendo de 0,60 (0,32). CONCLUSÃO: O exercício de agachamento associado à adução da coxa promoveu uma maior ativação muscular do VMO, além de aumentar a atividade muscular do GMed.

BACKGROUND: Hip and knee muscle weaknesses have been associated with the onset of anterior knee pain (AKP). Therefore, the understanding of how squats exercises can be performed in order to optimize the electrical activity of these muscles is relevant for physical therapy treatments. OBJECTIVE: To compare the electromyographic activity of patella and pelvic stabilizers during traditional squat and squat associated with isometric hip adduction or abduction in subjects without AKP. METHODS: Electromyography signals were captured using double-differential electrodes at the vastus medialis obliquus (VMO), vastus lateralis obliquus (VLO), vastus lateralis longus (VLL) and gluteus medium (GMed) in 15 healthy and sedentary women during squats exercises: traditional and associated with hip adduction and hip abduction with load of 25% of body weight. Linear mixed models with significance level of 5% were used for data analysis. RESULTS: Squat associated with hip adduction and abduction produced electromyographic activity of GMed of 0.47 (0.2) and 0.59 (0.22) respectively, while conventional squat produced an electromyiographic activity of 0.33 (0.27). The higher VMO activity was 0.59 (0.27) during the isometric contraction in the squat associated with hip adduction. The higher VLO activity was 0.60 (0.32) during isometric contraction in the squat associated with hip abduction. CONCLUSION: Squat exercise associated with hip adduction increased VMO muscle activity as well as the activity of GMed activity.

Foram analisadas as concentrações de mercúrio total (THg) em tecido muscular do tubarão azul Prionace glauca e do teleósteo Xiphias gladius, vulgarmente conhecido como espadarte, provenientes das regiões sul e sudeste da costa brasileira, para verificar se estas se encontram dentro dos padrões legais para consumo humano. As amostras foram obtidas utilizando-se o programa REVIZEE, de agosto a setembro de 2001, e por intermédio de uma empresa de pesca em Itajaí, Santa Catarina. Foi analisado um total de 95 espécimes, testando-se as correlações entre THg, comprimento (cm) e peso (kg). As concentrações de mercúrio total em todas as amostras variaram de 0,13 a 2,26µgg-1 (peso úmido). A média de mercúrio total em P. glauca foi de 0,76 ± 0,48µgg-1 (p.u.), e em X. gladius foi de 0,62 ± 0,31µgg-1 (p.u.) com diferença não significativa (teste Mann-Whitney, p < 0,05). Em cerca de 16% das amostras, o THg excedeu o limite de 1µgg-1 (Agência Nacional de Vigilância Sanitária) e em 62% excedeu o limite de 0,5µgg-1 (Organização Mundial da Saúde - OMS). O consumo regular (100 g.dia-1) de P. glauca e de X. gladius resultaria em uma ingestão diária de THg que excederia em mais de duas vezes o limite diário de ingestão recomendado pela OMS.

Total mercury (THg) was analyzed in muscle tissue from the blue shark Prionace glauca and the swordfish Xiphias gladius, obtained from the South and Southeast coast of Brazil, to verify compliance with current limits for human consumption. Samples were obtained through the REVIZEE Program and a commercial fishery in Itajaí, Santa Catarina State. A total of 95 specimens were analyzed (48 X. gladius and 47 P. glauca), and correlations were checked between THg and fish length and weight. THg ranged from 0.13 to 2.26µgg-1 (fresh weight), and there was no significant difference between the means for P. glauca, 0.76 ± 0.48µgg-1 (f.w.) and X. gladius, 0.62 ± 0.31 (Mann-Whitney test, p < 0.05). In 16% of samples, THg was above the limits set by the National Health Surveillance Agency (ANVISA), namely 1µgg-1, and 62% exceeded the World Health Organization (WHO) limit of 0.5µgg-1. The ingestion of 100g/ day-1 of P. glauca or X. gladius would result in a daily THg intake of more than twice the WHO (1990) suggested limit.

Foram analisadas as concentrações de mercúrio total (THg) em tecido muscular do tubarão azul Prionace glauca e do teleósteo Xiphias gladius, vulgarmente conhecido como espadarte, provenientes das regiões sul e sudeste da costa brasileira, para verificar se estas se encontram dentro dos padrões legais para consumo humano. As amostras foram obtidas utilizando-se o programa REVIZEE, de agosto a setembro de 2001, e por intermédio de uma empresa de pesca em Itajaí, Santa Catarina. Foi analisado um total de 95 espécimes, testando-se as correlações entre THg, comprimento (cm) e peso (kg). As concentrações de mercúrio total em todas as amostras variaram de 0,13 a 2,26µgg-1 (peso úmido). A média de mercúrio total em P. glauca foi de 0,76 ± 0,48µgg-1 (p.u.), e em X. gladius foi de 0,62 ± 0,31µgg-1 (p.u.) com diferença não significativa (teste Mann-Whitney, p < 0,05). Em cerca de 16% das amostras, o THg excedeu o limite de 1µgg-1 (Agência Nacional de Vigilância Sanitária) e em 62% excedeu o limite de 0,5µgg-1 (Organização Mundial da Saúde - OMS). O consumo regular (100 g.dia-1) de P. glauca e de X. gladius resultaria em uma ingestão diária de THg que excederia em mais de duas vezes o limite diário de ingestão recomendado pela OMS.

Total mercury (THg) was analyzed in muscle tissue from the blue shark Prionace glauca and the swordfish Xiphias gladius, obtained from the South and Southeast coast of Brazil, to verify compliance with current limits for human consumption. Samples were obtained through the REVIZEE Program and a commercial fishery in Itajaí, Santa Catarina State. A total of 95 specimens were analyzed (48 X. gladius and 47 P. glauca), and correlations were checked between THg and fish length and weight. THg ranged from 0.13 to 2.26µgg-1 (fresh weight), and there was no significant difference between the means for P. glauca, 0.76 ± 0.48µgg-1 (f.w.) and X. gladius, 0.62 ± 0.31 (Mann-Whitney test, p < 0.05). In 16% of samples, THg was above the limits set by the National Health Surveillance Agency (ANVISA), namely 1µgg-1, and 62% exceeded the World Health Organization (WHO) limit of 0.5µgg-1. The ingestion of 100g/ day-1 of P. glauca or X. gladius would result in a daily THg intake of more than twice the WHO (1990) suggested limit.

Neste trabalho, o corante azul de metileno foi imobilizado na superfície do acetato de celulose modificado com dióxido de titânio produzindo um material híbrido sólido denominado de CA-TiO2MB. O experimento produziu uma quantidade de 1,8 mmol g-1 de TiO2 incorporado no acetato de celulose e uma quantidade de 0,170 ± 0,005 mmol g-1 de azul de metileno adsorvido na superfície do CA-TiO2. Um eletrodo de pasta de carbono desse material foi usado para estudar a oxidação eletrocatalítica do ácido ascórbico pelas técnicas de voltametria cíclica e cronoamperometria. O pH da solução não afetou o potencial de pico de anódico nem a corrente de pico anódico ao variar de 3,0 a 7,0. A oxidação do analito ocorreu em 75 mV versus ECS em solução de KCl 1,0 mol L-1 e pH 7,0. A intensidade da corrente de pico anódico variou com a concentração de ácido ascórbico na faixa de 5,0 × 10-4 mol L-1 to 4,5 × 10-3 mol L-1, sendo observada uma correlação linear com um limite de detecção de 15 µmol L-1, limite de quantificação de 50 µmol L-1 e uma sensibilidade de 7,1 µA L mol-1. A resposta do eletrodo foi muito rápida, com um tempo decorrido de 1,0 s, mostrando potencial para ser utilizado como um sensor eletroquímico para a determinação de ácido ascórbico em produtos comerciais.

In this work, methylene blue dye was immobilized on the surface of cellulose acetate modified with titanium dioxide, producing a solid hybrid material designated as CA-TiO2MB. The experiment yielded an amount of 1.8 mmol g-1 of TiO2 incorporated in the cellulose acetate and an amount of 0.170 ± 0.005 mmol g-1 of methylene blue adsorbed onto CA-TiO2 surface. A carbon paste electrode of this material was used to study the electrocatalytic oxidation of ascorbic acid by cyclic voltammetric and chronoamperometric techniques. The pH of the solution had no effect on the anodic peak potential and anodic peak current when ranging from 3.0 to 7.0. The oxidation of the analyte occurred at 75 mV versus SCE in 1.0 mol L-1 KCl solution and pH 7.0. The intensity of the anodic peak current varied with the concentration of ascorbic acid from 5.0 × 10-4 mol L-1 to 4.5 × 10-3 mol L-1 and a linear correlation was observed, with a detection limit of 15 µmol L-1, quantification limit of 50 µmol L-1 and a sensitivity of 7.1 µA L mol-1. The electrode response was very fast, with an elapsed time of about 1.0 s, showing the potentiality to be utilized as an electrochemical sensor for determination of ascorbic acid in commercial samples.

As propriedades eletroquímicas dos corantes catiônicos, azul de meldola e azul de toluidina, imobilizados na superfície do acetato de celulose modificado com dióxido de titânio foram investigadas por voltametria cíclica. Os materiais sintetizados foram empregados como eletrodos de pasta de carbono. As propriedades mediadoras redox dos eletrodos modificados quimicamente com azul de meldola e azul de toluidina foram otimizadas utilizando um planejamento fatorial consistindo de dois níveis e quatro fatores com dois pseudo-pontos centrais (n=20 experimentos). A análise fatorial foi realizada para investigar as melhores condições de reversibilidade do processo redox tais como uma diminuição na separação entre os picos de potenciais anódico e catódico e razão de corrente próxima da unidade. Os fatores que apresentaram efeitos significantes na otimização global do sistema e que permitiram alcançar as melhores condições de reversibilidade de transferência de elétrons foram os fatores principais velocidade de varredura e tipo de eletrodo (azul de meldola ou azul de toluidina) além dos fatores de interação concentração do KCl × tipo de eletrodo (B×D) e a interação pH × [KCl] × velocidade de varredura (A×B×C). As melhores condições de reversibilidade eletroquímica obtidas foram: o eletrodo CA-TiO2-MB, KCl 1,0 mol L-1 como eletrólito suporte e velocidade de varredura de 10,0 mV s-1. Adicionalmente, o eletrodo modificado CA-TiO2-MB foi testado como sensor amperométrico para a determinação de NADH com um limite de detecção de 0,1 µmol L-1.

The electrochemical properties of meldola blue and toluidine blue cationic dyes immobilized on cellulose acetate surface modified with titanium dioxide were investigated by cyclic voltammetry. The materials synthesized were employed as carbon paste electrodes. The redox mediator properties of the meldola blue and toluidine blue chemically modified electrodes were optimized using a factorial design, consisting of two levels and four factors with two pseudo-central points (n= 20 experiments). The factorial analysis was carried out by searching for better reversibility of the redox process, such as the lowest separation between anodic and cathodic potential peaks and a current ratio near unity. The factors that presented significant effects on the overall optimization of the system to achieve the best conditions of the reversibility of electron transfer were the main factors scan rate and type of electrode (meldola blue or toluidine blue), besides the interaction factors KCl concentration × type of electrode (B×D) and the pH × [KCl] concentration × scan rate (A×B×C) interaction. The best electrochemical reversibility conditions obtained were: using the CA-TiO2-MB electrode, 1.0 mol L-1 KCl as supporting electrolyte, at scan rate of 10.0 mV s-1. Afterwards, the CA-TiO2-MB modified electrode was tested as an amperometric sensor for the determination of NADH, with a detection limit of 0.1 µmol L-1.