The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode / Os efeitos de nanotubos de TiO2 na resistência de união e radiopacidade de um cimento resinoso auto-adesivo no modo auto-polimerizável

Objective: The aim of this in vitro study w as t o analyze the influence of the titanium dioxide nanotubes i n a self-cure mode polymerization of a dual resin luting agent through push out bond strength and radiopacity tests. Material and Methods: After mixed with a commercial du al self-adhesive resin cement, three concentrations o f tit anium dioxide nanotubes (0.3, 0.6, and 0.9% by weight) we re analyzed in self-curing mode. T he bond strength to bovine root dentin and fi berglass posts was assessed with the push out bond str ength t est and was evaluated in three thirds (cervical, middle and apical) (n=10), followed by failure mode analysis (SEM), and the ISO standard 9917-2 was followed for radiopacity test (n=10). Data were statistically analyzed by one-way ANOVA test, followed by Tukey's test (α=0.05). Results: Reinforced self-adhesive resin cement with 0.6% titanium dioxide nanotubes showed significant difference compared to the control gr oup for push out test (p=0.00158). The modified groups did not s how significant difference among thirds (p=0.782). Radiopacity sh owed higher value for group w ith 0.9% titanium dioxide nanotubes in comparison w ith control group (p<0.001). Conclusion: The addition of titanium dioxide nanotubes to a self-adhesive resin cement increased the bond strength to dentin and radiopacity values in the self-cure polymerization mode (AU)

Objetivo: O objetivo deste estudo in vitro foi analisar a influência de nanotubos de dióxido de titânio na polimerização química de um agente cimentante resinoso dual através de testes de resistência à união e radiopacidade. Material e Métodos: Após misturado com um cimento resinoso auto-adesivo comercial, três concentrações de nanotubos de dióxido de titânio (0,3, 0,6 e 0,9% em peso) foram analisadas. A resistência da união para a dentina da raiz bovina e os pinos de fibra de vidro foi avaliada pelo teste de push-out e avaliada em três terços (cervical, médio e apical) (n = 10), seguido pelo análise de modo de falha (MEV) e a norma ISO 9917-2 foi seguido para teste de radiopacidade (n = 10). Os dados foram analisados estatisticamente pelo teste ANOVA um fator seguido do teste de Tukey (α = 0,05). Resultados: O cimento resinoso auto-adesivo reforçado com nanotubos de dióxido de titânio a 0,6% mostrou diferença significativa em comparação com o grupo controle para teste de push-out (p=0,00158). Os grupos modificados não mostraram diferença significativa entre os terços (p=0,782). A radiopacidade mostrou maior valor para o grupo com nanotubos de dióxido de titânio 0,9% em comparação com o grupo controle (p<0,001). Conclusão: A adição de nanotubos de dióxido de titânio a um cimento resinoso auto-adesivo aumentou a os valores de resistência de união à dentina e radiopacidade no modo de polimerização química do agente cimentante (AU)

Determination of chemical species of fluoride during uptake mechanism of glass-ionomer cements with NMR spectroscopy.

OBJECTIVE: The aim of the present study was to determine the chemical species formed inside glass-ionomer cements after fluoride uptake and to investigate the depth of penetration of fluoride ions within the cement matrix. METHODS: An experimental fluoride-free glass with composition 2SiO2-AlO3-CaO was produced. The glass powder was mixed with aqueous poly(acrylic acid) (PAA), and allowed to set. The resulting specimens were stored in 20ml KF solution with 1000ppm fluorine for 24h and then placed into the same amount of water as for 24h. A fluoride selective electrode was used to give the F concentration of the respective solutions. 19F MAS-NMR spectra were recorded on powdered cement specimens using a Bruker AVANCE-NEO 600 spectrometer. In addition, SEM observation and EDX chemical analysis were conducted on the cross-section of a carefully fractured specimen. RESULTS: Fluoride was shown to be mainly present in the surface layers of the specimen after placement in the KF solution, and only a small fraction was re-released into water. 19F NMR spectroscopy showed that AlF complexes were formed within the cement. SIGNIFICANCE: The fluoride taken up by a free-fluoride glass ionomer cement mostly occupies surface layers and is retained because it bonds to aluminum within the matrix. This finding explains why the majority of fluoride taken up by conventional glass ionomer cements is retained.

Translucency parameter of conventional restorative glass-ionomer cements.

OBJECTIVE: To evaluate the translucency parameter (TP) and contrast ratio (CR) of different conventional restorative glass-ionomer cements (GICs). MATERIALS AND METHODS: Eighteen brands of GICs were evaluated. Five disks of each material were made following ISO 9917-1. The luminous reflectance and Central Bureau of the International Commission on Illumination parameters of disks were evaluated using a colorimeter, against backings of white and black, to obtain the translucent parameter and contrast ratio of different brands of glass-ionomer cements. The correlation between translucency parameter and contrast ratio was assessed with the Pearson correlation test. The translucent and contrast ratio parameters values were submitted to the one-way ANOVA and Tukey test for multiple comparisons (p < 0.05). RESULTS: There was a strong inverse relationship between CR and TP (r2  = 0.94, p < 0.001). The contrast ratio decreased as translucency increased. There were significant differences in TP and CR among brands (p < 0.001). CONLUSIONS: GICs exhibit different translucency and contrast ratio behavior. Some brands of GICs presented very low TP and this condition would be unacceptable for areas with esthetic demands. In addition, TP and CR showed a strong linear relationship. CLINICAL SIGNIFICANCE: The results found in this study demonstrated that the knowledge of the translucency and CR of different conventional restorative GICs is important in order to guide clinicians in the selection of restorative GICs for anterior teeth.

Correlation between mechanical properties and stabilization time of chemical bonds in glass-ionomer cements.

The objective was to evaluate the compressive strength (CS), diametral tensile strength (DTS), flexural strength (FS), and Knoop microhardness (KH) of different conventional restorative glass-ionomer cements (GICs) and to correlate these mechanical properties (MP) with the stabilization time (ST) of their chemical bonds. Eighteen GICs were tested: Bioglass [B], Chemfil Rock [CR], Equia Forte [EF], Gold Label 2 [GL2], Gold Label 9 [GL9], Glass Ionomer Cement II [GI], Ionglass [IG], Ion Z[ IZ], Ionomaster [IM], Ionofil Plus [IP], Ionostar Plus [IS], Ketac Molar Easymix [KM], Magic Glass [MG], Maxxion R [Ma], Riva Self Cure [R], Vidrion R [V], Vitro Fil [VF] and Vitro Molar [VM]. The mechanical strength tests were performed in a universal testing machine. KH readings were done with a diamond indenter. STs were examined by Fourier Transform Infrared spectroscopy (FTIR). Data were analyzed with ANOVA and Tukey test (p<0.05). The Spearman rank test was used to evaluate the dependence between the MPs and ST results. The highest MP values were EF, GL2, GL9, GI and KM and the lowest for MG, MA, B, VF and IM. The longest ST was for GL2 and the shortest was for B. ST correlated positively with MP. GICs with longer chemical bonds ST are generally stronger and the ST value obtained from FTIR was useful in predicting the strength of GICs tested.

Correlation between mechanical properties and stabilization time of chemical bonds in glass-ionomer cements

Abstract The objective was to evaluate the compressive strength (CS), diametral tensile strength (DTS), flexural strength (FS), and Knoop microhardness (KH) of different conventional restorative glass-ionomer cements (GICs) and to correlate these mechanical properties (MP) with the stabilization time (ST) of their chemical bonds. Eighteen GICs were tested: Bioglass [B], Chemfil Rock [CR], Equia Forte [EF], Gold Label 2 [GL2], Gold Label 9 [GL9], Glass Ionomer Cement II [GI], Ionglass [IG], Ion Z[ IZ], Ionomaster [IM], Ionofil Plus [IP], Ionostar Plus [IS], Ketac Molar Easymix [KM], Magic Glass [MG], Maxxion R [Ma], Riva Self Cure [R], Vidrion R [V], Vitro Fil [VF] and Vitro Molar [VM]. The mechanical strength tests were performed in a universal testing machine. KH readings were done with a diamond indenter. STs were examined by Fourier Transform Infrared spectroscopy (FTIR). Data were analyzed with ANOVA and Tukey test (p<0.05). The Spearman rank test was used to evaluate the dependence between the MPs and ST results. The highest MP values were EF, GL2, GL9, GI and KM and the lowest for MG, MA, B, VF and IM. The longest ST was for GL2 and the shortest was for B. ST correlated positively with MP. GICs with longer chemical bonds ST are generally stronger and the ST value obtained from FTIR was useful in predicting the strength of GICs tested.

Positive correlation between fluoride release and acid erosion of restorative glass-ionomer cements.

OBJECTIVE: The aim of this study was to determine whether there is a correlation between acid erosion and fluoride release of conventional glass ionomer cements. METHODS: Ten specimens for each material were prepared for fluoride release tests and five for acid erosion tests separately. After placed in pH cycling solution, concentration of fluoride was measured by a fluoride-ion selective electrode each day for 15 days. For the acid erosion test, specimens were immersed in a lactic acid solution and their depth measured with a spring-loaded dial gauge. The data were submitted to 3-way ANOVA, followed by Tukey's test (p<0.05) RESULTS: All materials showed ability to elute fluoride in the 15 day period of the test, with the same pattern of high fluoride release at the first 24h. Despite this, the amount of fluoride released was statistically different among the 18 groups, with the highest for Maxxion R and the lowest for Chemfil Rock (p>0.05). The highest acid erosion values were registered for Magic Glass, Ion Z, VitroFil and Maxxion R, which exceeded the maximum stipulated by the relevant ISO test (ISO 9917-1). A positive linear correlation (r2=0.4886) was found for both properties, i.e., higher fluoride release is related to higher acid erosion. SIGNIFICANCE: Acid erosion and fluoride release are related properties of GICs, though factors such as pH and P/L ratio lead to differences between actual values for individual brands of these materials.

Clinical performance of the composite resin veneers: the minimally invasive approach / Desempenho clínico de facetas de resina composta: uma abordagem minimamente invasiva / Desempeño clínico de las carillas de resina compuesta: un enfoque mínimamente invasivo

Minimally invasive approach lead composite resin veneers restorations as a conservative and alternative treatment option, with the aim to improve the aesthetics anterior dentition. Clinically, this treatment reducing the clinical time and has a lower cost than indirect technique. In addition, new resin composite was developed to support the clinician to make more natural restorations. The present case report aim to evaluated the clinical performance of direct composite veneer technique was restored with 100% supra-nano spherical filler composite. A 39-year-old female, searched for restorative treatment of anterior teeth, which were unaesthetically altered. In the clinical examination, it was observed color alterations in maxillary left and right incisors and canines due to use of medicines, and bruxism. The treatment plan included an in-office dental bleaching, removal of inadequate anterior restorations and confection of composite veneers restorations. The dental bleaching was performed with hydrogen peroxide 35% activated by LED/laser in two sessions. Those restorations were performed using supra-nano spherical resin-based composite, color A1 for dentin and enamel, with direct composite laminate veneer technique. After six-month follow-up, the restorations presented good clinical aspect, absence of biofilm accumulation and abrasive wear. Therefore, direct veneer restorations may be alternative treatment for anterior teeth esthetic problems, suggesting a promising performance of these new composites(AU)

A abordagem minimamente invasiva torna as facetas de resina composta conservadoras e opção de tratamento alternativo para melhorar a estética da dentição anterior. Clinicamente, esse tratamento reduz o tempo operatório e tem um custo menor que a técnica indireta. Além disso, uma nova resina composta foi desenvolvida para ajudar o clínico a fazer restaurações mais naturais. O presente relato de caso tem como objetivo avaliar o desempenho clínico da técnica direta de faceta de resina composta de preenchimento 100% supra-nano-esférico. Paciente de 39 anos, sexo feminino procurou o tratamento restaurador dos dentes anteriores, que foram alterados inesteticamente. No exame clínico foram observadas alterações de cor nos incisivos superiores, esquerdo e direito, e caninos devido ao uso de medicamentos e bruxismo. O plano de tratamento incluiu clareamento dentário em consultório, remoção de restaurações anteriores inadequadas e confecção de facetas de resina composta. O clareamento dental foi realizado com peróxido de hidrogênio a 35% ativado por LED / laser em duas sessões. Essas restaurações foram realizadas utilizando resina composta supra-nano-esférica, cor A1 para dentina e esmalte, com técnica direta de laminado composto. Após seis meses de acompanhamento as restaurações apresentaram bom aspecto clínico, ausência de acúmulo de biofilme e desgaste abrasivo. Portanto, facetas diretas de resina composta podem ser um tratamento alternativo para problemas estéticos de dentes anteriores, sugerindo um desempenho promissor desses novos compósitos(AU)

El abordaje mínimamente invasivo hace que las facetas de resina compuesta conservadoras y opción de tratamiento alternativo para mejorar la dentición anterior estética. Clínicamente, este tratamiento reduce el tiempo clínico y tiene un costo menor que la técnica indirecta. Además, un nuevo compuesto de resina fue desarrollado para ayudar al clínico a hacer restauraciones más naturales. El presente relato de caso tiene como objetivo evaluar el desempeño clínico de la técnica directa de faceta de resina compuesta de relleno 100% supra-nano-esférico. Paciente de 39 años, sexo femenino buscó el tratamiento restaurador de los dientes anteriores, que fueron alterados intemporal. En el examen clínico se observaron alteraciones de color en los incisivos superiores, izquierdo y derecho, y caninos debido al uso de medicamentos y bruxismo. El plan de tratamiento incluyó blanqueamiento dental en consultorio, remoción de restauraciones anteriores inadecuadas y confección de facetas de resina compuesta. El blanqueamiento dental fue realizado con peróxido de hidrógeno al 35% activado por LED / láser en dos sesiones. Estas restauraciones se realizaron utilizando resina compuesta supra-nano esférica, color A1 para dentina y esmalte, con técnica directa de laminado compuesto. Después de seis meses de seguimiento las restauraciones presentaron buen aspecto clínico, ausencia de acumulación de placa dental y desgaste abrasivo. Por lo tanto, las facetas directas de resina compuesta pueden ser un tratamiento alternativo para problemas estéticos de dientes anteriores, sugiriendo un desempeño prometedor de estos nuevos compuestos(AU)

Understanding the interaction of resin composite with light for predictable aesthetic results in anterior teeth: A case report / Compreensão da interação das resinas compostas com a luz para resultados estéticos previsíveis em dentes anteriores: Relato de caso

This case report illustrates a conservative technique for reintervention on anterior composite restorations in a young patient with composite veneers. The treatment incorporated the use of photos and digital planning to establish a harmonious smile design. In order to conserve the dental tissues, existing resin composites restorations in maxillary anterior teeth were carefully removed to minimize enamel reduction, followed by a study of color and shade of teeth considering factors such as hue, chroma, luminosity, opacity, translucency and light effects. Eight direct veneers were built up with resin composite taking the optical properties of the material into account and their influence on the thickness of the layers that create specific light effects when superimposed on each other. To obtain excellent results with a predictable working protocol, nanohybrid composite systems facilitate good aesthetics, avoiding more invasive treatment in an economic manner.(AU)

O presente relato de caso ilustra uma técnica conservadora para a re-intervenção em restaurações diretas de resina composta em pacientes jovens. O tratamento consistiu em fotos e planejamento digital para obtenção de um desenho digital do sorriso individual e harmonioso. De acordo com os princípios de máxima conservação da estrutura dentária, as restaurações existentes nos dentes superiores anteriores foram criteriosamente removidas para minimizar a redução do esmalte, seguido do estudo de cor e sombra dos dentes considerando fatores como matiz, croma, valor, opacidade, translucidez e efeitos de luz. Oito facetas diretas foram realizadas em resina composta considerando as propriedades ópticas do material e a influência destas na espessura das camadas de resina para criar efeitos de luz singulares quando sobrepostas. Para a execução de uma odontologia estética e consciente, em associação a um protocolo de trabalho previsível, os sistemas de resinas compostas nanohibridas possibilitam resultados estéticos satisfatórios, evitando tratamentos mais invasivos de maneira economicamente viável.(AU)

Fluoride release of restorative commercial glass-ionomer cements / Liberação de flúor de diferentes marcas de ionômero de vidro convencional restaurador

Introdução: Inicialmente introduzidos por Wilson e Kent, os cimentos de ionômero de vidro (CIV) apresentam propriedades desejáveis. Desde desenvolvida em meados de 1980, a Técnica Restauradora Atraumatica (ART) é uma combinação de procedimento preventivo e restaurador introduzido para atendimento em áreas de condições precárias. A capacidade de liberação de flúor é uma das propriedade importante dos cimentos de ionômero de vidro e é fundamental para o sucesso em longo prazo das restaurações de ART. Novos CIVs tem emergido no mercado com melhores propriedades físicas, indicados pelos fabricantes para a técnica de ART. O objetivo desse estudo foi avaliar a liberação de flúor de nove cimentos de ionômero de vidro (CIV) convencionais restauradores brasileiros representando todas as marcas atualmente disponíveis no mercado. Eles foram divididos em indicados para ART [Maxxion-FGM-Brasil (MA), Ion Z-FGM-Brasil (IZ), Ionglass-Maquira-Brasil (IG), Bioglass R-Biodinâmica-Brasil (BG), Vitro Molar-Nova DFL-Brasil (VM)] e não indicados para ART [Vidrion-SSWhite-Brasil (VD), Ionomaster-Wilcos-Brasil (IM), Magic Glass-FGM-Brazil (MG), Vitro Fil-Nova DFL-Brasil (VF)]. Métodos: Espécimes (n=10) com 11.0mm de diâmetro e 3.0mm de espessura das nove marcas de CIV foram confeccionados de acordo com as instruções do fabricante em um molde de teflon. Os mesmos foram imersos em recipientes Falcon contendo 20ml de saliva artificial, fechados a 37º a as medidas de concentração de flúor foram realizadas após 1, 6, 12, 24, 72, 168, 336 horas. A concentração de flúor foi medida em duplicata, usando uma técnica micro analítica com um eletrodo sensível de íons flúor (Orion, modelo 96-09) unido a um potenciômetro (Procyon, modelo 720). Após os testes de normalidade (Shapiro-Wilk) e homogeneidade de variâncias (Levene) (p<0.05), os resultados foram submetidos a ANOVA e teste de Tukey para comparações múltiplas. Resultados: Em cada período avaliado foram observadas diferenças estatísticas entre os CIVs (p<0.05), apresentando o MA a maior quantidade de liberação de flúor para todos os períodos, com um total de 7.7 µg/mm² (p<0.05). O valor mínimo observado de liberação de flúor foi do VM, também em todos os períodos, totalizando em 1.14µg/mm². Observou-se que a maioria dos CIVs apresentou o mesmo padrão de liberação de flúor, indicados ou não para ART. Houve diferenças significativas especialmente em comparação com a quantidade de liberação de F- entre os CIVs indicados e não indicados para ART. Conclusão: De acordo com os resultados obtidos, a maioria dos CIVs testados apresentaram mesmo padrão de liberação de flúor. Contrário ao esperado, no geral, os CIVs indicados para ART apresentaram quantidade maior de liberação de flúor em comparação aos não indicados para ART.(AU)

Introduction: First discovered by Wilson and Kent, glass ionomer cements (GIC) present desirable properties. Atraumatic Restorative Technique (ART) is a combined preventive and restorative procedure developed for attendance in poor condition areas. Fluoride release (F- release) is one of the most important properties of GIC and it is essential to ART's approach high success rates. New GICs emerged in market with better physical properties and also indicated by manufacturers for the ART technique. The aim of this study was to evaluate the F- release of nine Brazilian conventional restorative GIC representing all national commercial brands available in the market. GIC were divided as indicated for ART [Maxxion-FGM (MA), Ion Z-FGM (IZ), Ionglass-Maquira (IG), Bioglass R-Biodinâmica (BG), Vitro Molar-Nova DFL (VM)] or not indicated for ART treatment [Vidrion-SSWhite (VD), Ionomaster-Wilcos (IM), Magic Glass-FGM (MG), Vitro Fil-Nova DFL (VF)]. Methods: Specimens (n=10) with 11.0mm in diameter and 3.0mm thick of the nine brands of GICs were manipulated in accordance to the manufacturer's instructions and inserted in a teflon mould. Those were immersed in falcon recipients containing 20ml of artificial saliva, closed at 37ºC in a laboratory oven and fluoride concentrations were measured after 1, 6, 12, 24, 72, 268, 336 hours. Fluoride concentration was measured in duplicate, using a micro analytical technique with an inverted fluoride ion selective electrode united at a potentiometer (Procyon, model 720). After the normality (Shapiro-Wilk) and homogeneity of variance (Levene) tests, results were submitted to ANOVA and Tukey Test for multiple comparisons (p<0.05). Results: In each evaluation time, significant statistical difference for amount and pattern of fluoride release was observed among the GICs (p<0.05), presenting Ma the highest fluoride release in all times, with a total of 7.7 µg/mm² (p<0.05). The lowest fluoride release was observed for VM in all times, with a total of 1.14 µg/mm². Most of GICs presented same pattern of F- release, indicated or not for ART. There was statistical significant difference especially when comparing F- release of GICs indicated for ART and those not indicated for ART (p<0.05). Conclusion: According to the results obtained, Brazilian commercial GICs tested presented similar pattern of F- release. Contrary to expected, most of GICs indicated for ART showed higher amount of fluoride release in comparison to those not indicated for ART. (AU)

Estudo e fabricação de dispositivos inteligentes (línguas e narizes eletrônicos) visando à discriminação de contaminação em alimentos / Study and development of smart devices (electronic nose and tongues) aiming at discrimination of contamination in food samples

A proposta da presente tese foi desenvolver dispositivos inteligentes (língua e nariz eletrônicos/ colorimétrico) de baixo custo para discriminar amostras de alimentos contaminados quimicamente e biologicamente. Um dispositivo "optoeletrônico" à base de membranas poliméricas coloridas com indicadores de pH foi utilizado para discriminar compostos voláteis emitidos por micro-organismos (aminas liberadas pelos processos de deterioração dos alimentos e que são produto da descarboxilação de aminoácidos em alimentos predominantemente proteicos). As aminas avaliadas nesse estudo foram: isobutilamina, isopentilamina e trietilamina. O limite de detecção de 5 ppm das aminas foi alcançado utilizando o dispositivo "optoeletrônico" e, esse sistema, também foi testado em amostras reais de carne contaminadas obtendo uma boa discriminação das amostras com e sem as aminas. Aminas biogênicas (cadaverina, tiramina e putrescina) também foram testadas obtendo uma separação pelo gráfico de escores. Em uma segunda etapa o dispositivo também foi avaliado para discriminar quatro espécies de bactérias (Klebsiella pneumoniae, Proteus vulgaris, Proteus mirabilis e Escherichia coli) incubadas a 37°C e 25°C. Em ambos os casos o dispositivo inteligente utilizou um smartphone para registrar as imagens que atuou como detector para extração dos dados de RGB das imagens. A partir dessas informações (valores de RGB), as ferramentas quimiométricas PCA (do inglês Principal Component Analysis, Análise de Componentes Principais) e HCA (do inglês Hierarchical Cluster Analysis, Análise de Agrupamentos Hierárquicos) foram utilizadas para discriminar as amostras e a k-NN (do inglês kth Nearest Neighbor, k- vizinhos mais próximos) para validar o método. Em uma terceira etapa, uma língua eletrônica voltamétrica foi fabricada para discriminar amostras de leite adulteradas com melamina, ureia e formaldeído contendo concentrações finais de 0,95; 4,16 e 10,0 mmol L-1, respectivamente. Essa língua voltamétrica foi composta por três eletrodos metálicos: platina, ouro e cobre e dados voltamétricos foram utilizados como dados de entrada para as ferramentas quimiométricas (PCA e HCA). Foram testados três tipos de leite (integral, desnatado e semidesnatado) de três diferentes marcas e todos eles puderam ser discriminados com sucesso. O trabalho também apresenta a utilização de MIPs (polímeros molecularmente impressos - do inglês, molecularly imprinted polymers) como alternativa para detecção e discriminação de alimentos contaminados fazendo uso da impressão (cavidades) de substâncias químicas contaminantes ou das proteínas específicas de cada micro-organismo presente no processo de deterioração dos alimentos

The present thesis aimed at development of low cost smart devices (electronic tongue and colorimetric nose) to discriminate chemically and biologically contamination in food samples. An "optoelectronic" plastic-based device with colored membranes contained pH indicator was used to discriminate volatile compounds released by microorganisms, due to the deterioration process of protein in food by the organisms. The amines evaluated in this study were: isobutylamine, isopentylamine and triethylamine, achieving a detection limit of 5 ppm. Such system was also tested in real meat samples contaminated with individual amines obtained a good discrimination of samples with and without studied compounds. Biogenic amines (cadaverine, tyramine and putrescine) were also tested and discriminated. In a second step, the device was also evaluated to discriminate four bacteria species (Klebsiella pneumoniae, Proteus vulgaris, Proteus mirabilis and Escherichia coli) incubated at 37 ° C and 25 ° C. In both cases, a smartphone was used as detector to extract RGB values of the samples. From extracted information (RGB values), the chemometric tools PCA (Principal Component Analysis) and HCA (Hierarchical Cluster Analysis) were used to discriminate samples and k-NN (kth Nearest Neighbor) was evaluated to validate the method. In a third stage, a voltammetric electronic tongue was developed to discriminate adulterated milk samples with melamine, urea and formaldehyde. This voltammetric electronic tongue was fabricated using three working electrodes: platinum, gold and copper and the voltammetric data was used as input data for chemometric tools (PCA and HCA). Three types of milk (whole, skimmed and semi-skimmed) from three different brands were tested and all of them could be successfully discriminated

A copper interdigitated electrode and chemometrical tools used for the discrimination of the adulteration of ethanol fuel with water.

A new approach for the discrimination of the adulteration process of ethanol fuel with water is reported using a copper interdigitated electrode and chemometrical tools. The sensor was constructed using copper sheets with non-chemical modification of the electrode surface. The discrimination process was performed using capacitance values recorded at different frequencies (1,000 Hz to 0.1 MHz) as the input data for non-supervised pattern recognition methods (PCA: principal component analysis and HCA: hierarchical cluster analysis). The relative standard deviation for the capacitance signals obtained from ten independent interdigitated sensors was below 5.0%. The ability of the device to differentiate non-adulterated ethanol samples from those adulterated with water was demonstrated. In all analysed cases, there was good separation between the different samples in the score plots and the dendrograms obtained from PCA and hierarchical cluster analyses, respectively. Furthermore, the water content was quantified using a PCA approach. The results were consistent with those obtained using the Karl-Fischer method at a 95% confidence level, as measured using Student's t-test.