Determination of components and contaminants in cachaça using methods based on digital image analysis

Determinação de componentes e contaminantes em cachaça empregando métodos baseados em análise de imagem digital. Orientador: Willian Toito Suarez. Por meio desse trabalho, propõe-se o desenvolvimento e aplicação de quatro métodos analíticos simples, rápidos e de baixo custo. Foi empregado um smartphone como instrumento analítico para determinação de componentes e contaminantes em amostras de cachaças. Os métodos baseiam-se na decomposição das imagens em modelos algébricos, sendo o RGB, o modelo empregado. Desta feita, foi proposto uma metodologia analítica para determinação do teor de acidez volátil nas bebidas empregando o alaranjado de metila e sua propriedade halocrômica. A faixa dinâmica linear para determinação da acidez volátil foi linear de 25 a 275 mg/100 mL de álcool anidro com R 2 =0,99 e com limites de detecção e quantificação de 6,70 e 22,33 mg/100 mL, respectivamente. Além disso, validou-se uma metodologia analítica para determinação de açúcares em cachaça, baseado na redução do Cu 2+ à Cu + pelos açúcares redutores (sacarose e frutose) e formação do complexo colorido entre Neocuproína e Cu 1+ em meio alcalino. A curva analítica foi linear de 0,1 a 15 g L −1 para glicose e frutose com limites de detecção de 0,012 g L −1 e 0,010 g L −1 , respectivamente. Ademais, foi proposto um método para determinação de Cu 2+ empregando uma tiocarbazona como reagente complexante. Esta reação é inédita na literatura, e foi possível obter uma reação altamente sensível e mais seletiva que outros complexantes, como por exemplo, a cuprizona. Após otimizar a reação, obteve-se uma curva analítica para determinar Cu 2+ entre 0,25 e 6,75 mg L -1 com um desvio padrão relativo (n = 5) de 3,2%, bem como um limite de detecção de 0,18 mg L -1 usando um volume de amostra de 400 μL . Por fim, foi proposto um método para determinação simultânea de Cu 2+ e furfural em amostras de cachaças usando um sistema bifásico e ferramentas quimiométricas. O furfural reage com a anilina em meio ácido formando furfulidenanelina, que apresenta coloração rósea. Por outro lado, Cu 2+ reage com Cuprizona em meio básico para formar um complexo azul. A regressão por mínimos quadrados parciais (PLS) foi utilizada para construir os modelos de predição dos teores de Cu 2+ e furfural em amostras de cachaças. O método desenvolvido foi eficaz para estimar os valores de ambos analitos em cachaças, com erro absoluto médio de 0,2 mg/L para o modelo Cu 2+ , e 0,3 mg/100 mL de álcool anidro para o modelo furfural. Todos os métodos analíticos demonstraram alta exatidão e precisão em relação aos valores encontrados pelos métodos de referência. Não obstante, apresentaram faixas de recuperação adequadas, demonstrando ausência de efeitos de matriz significativos nas amostras estudadas. Sendo assim, as metodologias propostas apresentam como uma alternativa altamente promissora para análises dos analitos in situ e pode auxiliar os produtores na fabricação de um produto seguro para consumo e com propriedades sensoriais superiores. Palavras-chave: Análise de imagem digital. Cachaça. Smartphone.Through this work, we propose the development and application of four simple, fast and low-cost analytical methods using a smartphone as an analytical instrument for the determination of components and contaminants in samples of cachaça. The methods are based on the decomposition of images into algebraic models, with RGB being the model used. The methods are based on the decomposition of images into algebraic models, with RGB being the model used. This time, an analytical methodology was proposed to determine the volatile acidity content in beverages using methyl orange and its halochromic property. The linear dynamic range for determination of volatile acidity was linear from 25 to 275 mg/100 mL of anhydrous alcohol with R 2 =0.99 and detection and quantification limits of 6.70 and 22.33 mg/100 mL, respectively. Furthermore, an analytical methodology was validated for the determination of sugars in cachaça, based on the reduction of Cu 2+ to Cu + by reducing sugars (sucrose and fructose) and formation of the colored complex between Neocuproine and Cu 1+ in alkaline medium. The calibration curve was linear from 0.1 to 15 g L −1 for glucose and fructose with detection limits of 0.012 g L −1 and 0.010 g L −1 , respectively. Furthermore, a method for Cu 2+ determination was proposed using a thiocarbazone as a complexing reagent. This reaction is unprecedented in the literature, and it was possible to obtain a highly sensitive and more selective reaction than other complexing agents, such as cuprizone. After optimizing the reaction, an analytical curve was obtained to determine Cu 2+ between 0.25 and 6.75 mg L -1 with a relative standard deviation (n = 5) of 3.2%, as well as a detection limit of 0.18 mg L -1 using a sample volume of 400 μL. Finally, a method was proposed for the simultaneous determination of Cu 2+ and furfural in cachaça samples using a two-phase system and chemometric tools. Furfural reacts with aniline in an acidic medium to form furfulidenanelin, which is pink in color. On the other hand, Cu 2+ reacts with cuprizone in basic medium to form a blue complex. Partial least squares regression (PLS) was used to build prediction models for Cu 2+ and furfural in cachaça samples. The method developed was effective to estimate the values of both analytes in cachaças, with a mean absolute error of 0.2 mg/L for the Cu 2+ model, and 0.3 mg/100 mL of anhydrous alcohol for the furfural model. All analytical methods demonstrated high accuracy and precision in relation to the values found by the reference methods. Nevertheless, they showed adequate recovery ranges, demonstrating the absence of significant matrix effects in the samples studied. Therefore, the proposed methodologies present a highly promising alternative for in situ analyte analysis and can help producers in the manufacture of a safe product for consumption and with superior sensory properties. Keywords: Digital image analysis. Cachaça. Smartphone.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Microfludic paper-based devices for determination of copper in sugar cane spirits

Neste trabalho, foram desenvolvidos dispositivos microfluíficos à base de papel (µPADs), almejando dois propósitos: i) propor um método que possibilite identificar, por meio de um sistema point of care, de modo simples e rápido, a presença da contaminação de Cu 2+ em cachaça nos próprios alambiques onde são fabricadas, e, por último, ii) quantificar o teor da substância através dos dispositivos construídos, sob o auxílio de um smartphone. Os microdispositivos foram funcionalizados com cuprizona e por meio de um planejamento experimental Box-Behnken o método foi otimizado com intuito de se obter as melhores condições reacionais. Embora, recentemente, o nosso grupo tenha desenvolvido diversas metodologias para a determinação de contaminantes em cachaça empregando smartphones, estas não se disseminaram no ambiente de produção, sobretudo em virtude da resistência à compra de reagentes e micropipetas, além dos obstáculos referentes à manipulação do smartphone como uma ferramenta analítica. Desta feita, pela primeira vez, o respectivo trabalho propõe um dispositivo microfluídico à base de papel para identificação de Cu 2+ em cachaça, que, em razão da simplicidade e alta portabilidade, pode ser facilmente inserido no meio produtivo, permitindo aos próprios produtores, de modo rápido e seguro, realizar as análises necessárias das cachaças fabricadas. O método obteve sucesso em ambas as condições propostas, uma vez que, a partir da análise qualitativa, alcançou-se acurácia de 93% nas respostas dos analistas em relação à possibilidade de contaminação das amostras com o metal de interesse. Ademais, por meio do método quantitativo, foi possível determinar o teor do metal em nível de concordância estatística com o método de referência.In this work, microfluidic paper-based devices (μPADs) were developed, aiming at two goals: i) to propose a method that allows to identify, through a point of care system, in a simple and fast way, the presence of contamination of Cu 2+ in cachaça, in the stills where they are manufactured, and, finally, ii) quantify the content of the substance through the devices built, through a smartphone. The microdevices were functionalized with cuprizone and through a Box-Behnken experimental design the method was optimized with the purpose of obtaining the best reactional conditions. Although our group has recently developed several methodologies for the determination of contaminants in cachaça using smartphones, they have not spread in the production environment, mainly due to resistance to the purchase of reagents and micropipettes, as well as obstacles related to the manipulation of the smartphone as an analytical tool. This time, for the first time, the paper proposes a paper-based microfluidic device for the identification of Cu 2+ in cachaça, which, due to the simplicity and high portability, can be easily inserted into the productive environment, allowing producers, in a fast way and safe, to carry out the necessary analyzes of the manufactured cachaças. The method was successful in both conditions, since, from the qualitative analysis, 93% accuracy was obtained in the analysts' responses regarding the possibility of contamination of the samples with the metal of interest. In addition, through the quantitative method, it was possible to determine the content of the metal at the level of statistical agreement with the reference method

Smartphone application for methanol determination in sugar cane spirits employing digital image-based method

A simple, accurate, and low-cost analytical procedure for methanol determination in sugarcane spirits (cachaça) employing analysis of digital images is presented. A portable system with cheap materials and lighting system to obtain images from a smartphone was built and an RGB system was used for analytical purposes. The reaction for determination of methanol in beverages consists in methanol oxidation to methanal, and consequent formation of a violet chromophore in the presence of chromotropic acid on heating in an oven at 80 °C for 15 min. From the system optimization, analytical curves that showed good linearity for the green channel (from RGB) was built, with regression coefficient (R^ 2) of 0.998. Relevant matrix effect in the samples was not verified, since the recovery percentage ranged from 83 to 110%. The results of methanol concentration in six cachaça samples obtained by the developed method were compared with using the spectrophotometric method with a confidence level of 95% (n = 3). The developed method has some economic and environmental benefits, since it has low reagent consumption with 800 μL per measured spot, as well as, it presents cheap and handle-easy devices, which encourages the quality control of this toxic and undesirable contaminant for smallholders and industries on production of sugar cane spirits

A simplistic portable LED-Based photometer for in situ determination of copper in sugarcane spirits

A low-cost and portable LED-based photometer was developed and applied for in situ determination of copper in sugarcane spirit. The determination was based on the chelation reaction between copper(II) and cuprizone (bis(cyclohexanone)oxalyldihydrazone). After optimizing the best experimental variables, a dynamic linear range to determine copper(II) was linear from 1.0 to 12.0 mg L−1 (r2 = 0.999) with the limits of detection and quantification of 0.20 and 0.70 mg L−1, respectively. The recovery of copper ranged from 96.5 to 104.4%. The paired t test was performed, and the results agreed at 95% level of confidence. The analytical method LED-based photometer demonstrated that it can be employed to determine copper in sugarcane spirit for quality purpose, e.g., small rural producers can evaluate the drink quality before bottling due to the easy handling, portability, fast response, and low-cost of the materials used

In situ determination of urea in milk employing a portable and low-cost LED photometer

A low-cost and portable LED photometer was developed and applied for the in situ determination of urea in milk. The determination was based on Berthelot’s reaction. After optimization, the best experimental variables, the detection limit and quantification limit were 1.8 × 10^−4 and 8.0 × 10^−4 mol L^−1, respectively. The percentage recovery varied between 95.6 and 105%. The paired t test was performed for the cow and goat milk determination and the results agreed at a 95% level of confidence for the in situ determination. Supported by the results, the analytical method based on LED photometer demonstrated that it can be employed for urea determination in food production for quality purpose, and small rural producers can evaluate the quality of herd feeding due to the easy handling, portability, fast instrumental response, and low cost of the materials used

Desenvolvimento e validação de metodologia analítica baseada em imagens digitais de spot tests para determinação de etanol em cachaça

A análise de imagens digitais é um método analítico baseado na decomposição da imagem, cujos os valores RGB variam proporcionalmente com a concentração do analito. Para a determinação de etanol, empregou-se a reação de óxido-redução na qual o cromo (VI) é reduzido a cromo (III) ou cromo (II), sendo o etanol oxidado a aldeído acético, gerando mudança da cor amarelo-alaranjada para verde-azulada. Foi obtida uma curva analítica linear no intervalo de 10 a 70 % v/v de etanol, com coeficiente de regressão r 2 = 0,991. Os limites de detecção e de quantificação foram iguais à 1,72 % v/v e 5,74 % v/v. Seis amostras de cachaça foram analisadas empregando o método proposto e um método picnométrico, e conclui-se que três delas apresentaram teor de etanol fora da faixa permitida pela legislação. O método analítico baseado em imagens digitais mostrou-se versátil, preciso, exato, de custo baixo e com baixa geração de resíduos, muito útil para análises in situ.Digital image analysis is an analytical method based on the decomposition of the image through an RGB color model, which values of RGB varies in proportion to the analyte concentration. For the determination of ethanol, it was employed the reaction of redox in which chromium (VI) is reduced to chromium (III) or chromium (II) and the ethanol is oxidized to acetaldehyde, generating change in the yellow-orange color to blue-green. By determining the ethanol content, a linear calibration curve in the range from 10 to 70% v/v ethanol was obtained, with a coefficient of regression r 2 = 0.9910. Limits of detection and quantification respectively equal to 1.72 % v/v and 5.74% v/v also were obtained. six cachaça samples were analyzed using the digital image and the picnometric method. The results showed that three of them had ethanol content outside the range permitted by law. Besides the image capture system is versatile, accurate, precise, low cost, low waste generation, being it very useful for in situ analysis

A digital image method of spot tests for determination of copper in sugar cane spirits

In this work the development and validation of analytical methodology for determination of copper in sugarcane spirit samples is carried out. The digital image based (DIB) method was applied along with spot test from the colorimetric reaction employing the RGB color model. For the determination of copper concentration, it was used the cuprizone - a bidentate organic reagent - which forms with copper a blue chelate in an alkaline medium. A linear calibration curve over the concentration range from 0.75 to 5.00 mg L^−1 (r2 = 0.9988) was obtained and limits of detection and quantification of 0.078 mg L^−1 and 0.26 mg L^−1 were acquired, respectively. For the accuracy studies, recovery per- centages ranged from 98 to 104% were obtained. The comparison of cooper concentration results in sugar cane spirits using the DIB method and Flame Atomic Absorption Spectrometry as reference method showed no significant differ- ences between both methods, which were performed using the paired t-test in 95% of confidence level. Thus, the spot test method associated with DIB allows the use of devices as digital cameras and smartphones to evaluate colorimetric reaction with low waste generation, practicality, quickness, accuracy, precision, high portability and low-cost