This study describes the use of uncured polydimethylsiloxane (PDMS) as a binder agent to prepare carbon paste electrodes (CPEs). A comparative study between the properties of CPEs prepared with PDMS and mineral oil Nujol®, the most common binder agent for CPEs, was carried out. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry showed that PDMS-CPEs presented higher electrical conductivity, active electrochemical area, and wider useful potential window compared with Nujol®-CPEs. Moreover, PDMS-CPEs were more stable in aqueous mixtures containing 50% (v/v) of ethanol or methanol than Nujol®-CPEs. PDMS-CPEs have also provided higher sensitivity and lower limit of detection to propranolol than Nujol®-CPE. Therefore, this study demonstrated that PDMS is a promising alternative binder agent able to produce CPEs with superior chemical/electrochemical stability and improved analytical performance.

A eletrooxidação da cisteamina (CA) foi estudada por eletrodos de pasta de nanotubos de carbono modificados com ácido 3,4-diidroxicinâmico (3,4-DHCA) usando voltametria cíclica, cronoamperometria e voltametria de varredura linear. Usando o eletrodo modificado, a cinética de eletrooxidação da CA foi consideravelmente intensificada através da redução do potencial anódico por meio de uma reação catalítica. O mecanismo de comportamento eletroquímico da CA na superfície do eletrodo modificado foi analisado por vários métodos eletroquímicos, na presença de mediador. O eletrodo modificado preparado apresentou respostas voltamétricas com alta sensibilidade para CA, o que o torna muito adequado para a detecção de CA em quantidades de traço. Um intervalo dinâmico linear de 0,25-400 µmol L-1 para a CA foi obtida em solução tamponada com pH 7,0. O limite de detecção foi de 0,09 µmol L-1.

The electrooxidation of cysteamine (CA) was studied by modified carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) using cyclic voltammetry, chronoamperometry and linear sweep voltammetry. Using the modified electrode, the kinetics of CA electrooxidation was considerably enhanced by lowering the anodic over-potential through a catalytic fashion. The mechanism of CA electrochemical behavior at the modified electrode surface was analyzed by various electrochemical methods in the presence of mediator. The prepared modified electrode showed voltammetric responses with high sensitivity for CA, making it very suitable for the detection of CA at trace levels. A linear dynamic range of 0.25-400 µmol L-1 for CA was obtained in buffered solutions with pH 7.0. The limit of detection was 0.09 µmol L-1.