Caffeine determination at a carbon fiber ultramicroelectrodes by fast-scan cyclic voltammetry

Abstract

A possibilidade de determinação eletroanalítica de cafeína com ultramicroeletrodo de fibra de carbono (CF-UME), utilizando voltametria de varredura rápida, foi avaliada. Os CF-UMEs foram submetidos a pré-tratamentos eletroquímicos. Parâmetros como o número de ciclos para cálculo da média, velocidade de varredura, intervalo de potencial e o tipo de pré-tratamento superficial foram otimizados. Sob condições otimizadas, foi possível alcançar intervalo linear de resposta entre 10,0 e 200 mmol L-1 , obtendo limites de detecção de 3,33 mmol L-1. O método foi aplicado à determinação de cafeína em amostras comerciais de fármacos, com erros entre 1,0 e 3,5% em relação ao valor do rótulo e valores de adição e recuperação de 97-114%. Caffeine determination using a fast-scan voltammetric procedure at a carbon fiber ultramicroelectrode (CF-UME) is described. The CF-UME was submitted to electrochemical pretreatment. Parameters such as number of acquisition cycles, scan rate, potential window, and the electrochemical surface pretreatment were optimized. Using the optimized conditions, it was possible to achieve a LDR from 10.0 up to 200 mmol L-1 , with a LOD of 3.33 mmol L-1. The method has been applied in the determination of caffeine in commercial samples, with errors of 1.0-3.5% in relation to the label values and recoveries of 97-114% within the linear range.

Simple electrochemical sensor for caffeine based on carbon and Nafion-modified carbon electrodes

“…Thus it can be deduced that 2 electrons are involved in the first step. The full oxidation mechanisms involves two oxidation steps, the second being a 2e -2H+ oxidation, involving overall 4 eand 4 H + (Nunes, & Cavalheiro, 2012;Mersal, 2012;Spataru, et al, 2002;Sun, et al, 2011).…”

“…Other sensors mostly work in very acidic media: sulphuric acid (Brunetti, Desimoni, & Casati, 2007, Martínez-Huitle, et al, 2010Sun, et al, 2011, Yang, et al, 2010, nitric acid (Amare, &Admassie, 2012) or perchloric acid (Alizadeh, et al, 2010;Švorc, et al, 2012). Few articles report the use of buffer solutions, for example pH 6.0 or 7.4 respectively (Aklilu, Tessema, & Redi-Abshiro, 2008;Nunes, & Cavalheiro 2012).…”

“…Some recent electrochemical detection methods for caffeine have been reported. These include using boron-doped diamond electrodes (BDD) (Švorc, et al, 2012), Nafion-modified BDD (Martínez-Huitle, et al, 2010), cathodically-pretreated BDD electrodes (Lourenção, et al, 2009), 1,4-benzoquinone or molecularly imprinted polymer modified carbon paste electrodes (Aklilu, Tessema, & Redi-Abshiro, 2008;Alizadeh, et al, 2010), Nafion/carbon nanotube (Yang, et al, 2010;Zhang et al, 2011) or Nafion/graphene modified electrodes (Sun, et al, 2011, Zhao, et al, 2011, carbon fibre ultramicroelectrodes (Nunes, & Cavalheiro, 2012), and polymer modified glassy carbon electrodes (GCE) (Amare, & Admassie, 2012). One report appeared on caffeine detection at a Nafion-modified glassy carbon electrode, the Nafion being used to both decrease the caffeine oxidation potential, so as not to overlap with oxygen evolution, and increase electrode sensitivity (Brunetti, Desimoni, & Casati, 2007).…”

Cyclic Voltammetric Investigation of Caffeine at Methyl Orange Modified Carbon Paste Electrode

“…The first step is a 2e -, 2H + oxidation of the C-8 to N-9 bond to give the substituted uric acid, followed by an immediate 2e -, 2H + oxidation to the 4, 5-diol analog of uric acid. The full oxidation mechanism involving overall 4eand 4H + [22][23][24][25].…”

Green Electrochemical Sensor for Caffeine Determination in Environmental Water Samples: The Bismuth Film Screen-Printed Carbon Electrode

“…Among these are liquid chromatography, 19 high performance liquid chromatography, 20,21 spectrophotometry, 22,23 and voltammetry. 1,2,[4][5][6][8][9][10][11][12][24][25][26][27][28][29][30][31][32][33][34]37 The advantages of voltammetry are in its high sensitivity, quick response and low apparatus cost. 10 Most frequently, a glassy carbon electrodes modified with Nafion, 11,24,25 graphene, 26 single-walled 27 and multiwalled carbon nanotubes are used.…”