Um eletrodo de pasta de carbono modificado com zeólitas e dopado com ferro(III) foi usado como um sensor eletroquímico de alta sensibilidade e seletividade para a determinação simultânea de pequenas quantidades de compostos biologicamente importantes como epinefrina (Ep) e tirosina (Tyr). Os resultados da voltametria de pulso diferencial (DPV) usando este eletrodo modificado mostra duas ondas anódicas bem traçadas para a oxidação da Ep e da Tyr, as quais tornam possíveis a determinação simultanêa destes compostos. A faixa linear de 0,9 a 216 mmol L -1 para a Ep em uma concentração fixa de 30 mmol L -1 Tyr em solução tampão fosfato, pH 3,0 foi obtida das medidas de DPV usando este eletrodo, com um coeficiente de correlação de 0,9998 e limite de quantificação igual a 0,44 mmol L -1 . A linearidade obtida para a Tyr na presença de 30 mmol L -1 de Ep, foi de 1,2 a 90 mmol L -1 com um coeficiente de correlação de 0,9989 e limite de quantificação de 0,32 mmol L -1 . O eletrodo modificado apresentou uma boa reprodutibilidade (RSD< 2.5%), baixo limite de quantificação (sub-micromolar) e alta sensibilidade para a detecção de ambos Ep e Tyr com uma elevada estabilidade em sua resposta voltamétrica. O desempenho analítico deste sensor tem sido avaliado para a detecção de epinefrina e tirosina em soro humano e em amostras farmacêuticas com resultados satisfatórios.A Zeolite modified carbon paste electrode doped with iron(III) was used as a highly sensitive and selective electrochemical sensor for simultaneous determination of minor amounts of epinephrine (Ep) and tyrosine (Tyr) as the biologically important compounds. The results of differential pulse voltammetry (DPV) using this modified electrode show two well-resolved anodic waves for the oxidation of Ep and Tyr ,which makes it possible for simultaneous determination of both compounds. A linear range from 0.9 to 216 mmol L -1 for Ep at a constant concentration of 30 mmol L -1 Tyr in buffered solution (phosphate buffer, pH 3.0) was obtained from DPV measurement using this electrode with a correlation coefficient of 0.9998 and a detection limit of 0.44 mmol L -1 . The linear range, which is obtained for Tyr in the presence of 30 mmol L -1 Ep, was in the range from 1.2 to 90 µmol L -1 with a correlation coefficient of 0.9989 and a detection limit of 0.32 mmol L -1 . The modified electrode had good reproducibility (RSD < 2.5%), low detection limit (sub-micromolar) and high sensitivity for the detection of both Ep and Tyr with a very high stability in its voltammetric response. The analytical performance of this sensor has been evaluated for detection of Ep and Tyr in human serum and in a pharmaceutical sample with satisfactory results.Keywords: Epinephrine, tyrosine, Fe(III) doped zeolite, modified carbon paste electrode IntroductionEpinephrine (Ep), Scheme 1 (a), often called adrenaline, is one of the most important neurotransmitters in mammalian central nervous systems, existing in the nervous tissue and body fluid, and controlling the nervous system in the performance of ...

Um eletrodo quimicamente modificado foi construído, baseado em eletrodo de carbono vítreo modificado por nanotubos de carbono de paredes múltiplas (ECV-NTCPM). O uso deste sensor na determinação de acetaminofeno (ACT), em meio aquoso tamponado, foi demonstrado. As medidas foram realizadas com utilização dos métodos de voltametria de pulso diferencial (VPD), voltametria cíclica (VC) e cronoamperometria (CA). A aplicação de VPD mostrou dois intervalos dinâmicos lineares. O primeiro intervalo dinâmico linear foi de 0,1 a 22 μmol L -1 , com equação de calibração Ip(μA) = 1,2782c (mmol L -1 ) + 0,2431 (R 2 = 0,9984) e o segundo intervalo dinâmico linear foi entre 26 e 340 μmol L -1 com equação de calibração Ip(μA) = 0,7793c (mmol L -1 ) + 11,615 (R 2 = 0,9986). O limite de detecção de 0,029 μmol L -1 (S/N = 3) foi obtido. O eletrodo modificado mostrou respostas eletroquímicas com alta sensitividade, excelente seletividade e estabilidade para determinação de ACT em condições ótimas, o que o torna um sensor adequado para detecção submicromolar de ACT em soluções. O desempenho analítico deste sensor foi avaliado para detecção de ACT em soro humano, urina humana e em preparações farmacêuticas com resultados satisfatórios.A chemically modified electrode is constructed based on multi-walled carbon nanotube modified glassy carbon electrode (MWCNTs/GCE). It was demonstrated that this sensor could be easily used for determination of acetaminophen (ACT) in aqueous buffered media. The measurements were carried out by application of differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA) methods. Application of DPV method showed two linear dynamic ranges. The first linear dynamic range was from 0.1 to 22 μmol L -1 , with a calibration equation of Ip(μA) = 1.2782c (mmol L -1 ) + 0.2431 (R 2 = 0.9984) and the second linear dynamic range was between 26 to 340 μmol L -1 with a calibration equation of Ip(μA) = 0.7793c (mmol L -1 ) + 11.615 (R 2 = 0.9986). A detection limit of 0.029 μmol L -1 (S/N = 3) was obtained. The modified electrode showed electrochemical responses with high sensitivity, excellent selectivity and stability for ACT determination at optimal conditions, which makes it a suitable sensor for submicromolar detection of ACT in solutions. The analytical performance of this sensor has been evaluated for detection of ACT in human serum, human urine and a pharmaceutical preparation with satisfactory results.Keywords: acetaminophen, carbon nanotube, modified glassy carbon, electrochemical sensor IntroductionAcetaminophen (N-acetyl-p-aminophenol) (ACT), also known as paracetamol, is a drug with antipyretic and analgesic action, frequently used in therapy and which has low toxicity when used at the recommended doses. 1 Nevertheless, the ease with which ordinary people can access this drug makes it frequently associated with overdoses, in this situation causing serious or even fatal hepatic damage. 2 An overdose of ACT can lead to the accumulation of toxic metabolites, which may cause severe an...

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Utilizing renewable energy to hydrogenate carbon dioxide into fuels eliminates massive CO2 emissions from the atmosphere and diminishes our need for using fossil fuels. This review presents the most recent developments for designing heterogeneous catalysts for the hydrogenation of CO2 to formate, methanol, and C2+ hydrocarbons. Thermodynamic challenges and mechanistic insights are discussed, providing a strong foundation to propose a suitable catalyst. The main body of this review focuses on nanostructured catalysts for constructing efficient heterogeneous systems. The most important factors affecting catalytic performance are highlighted, including active metals, supports and promoters that can potentially be used. The summary of the results and the outlook are presented in the final section. During the past few decades, heterogeneous CO2 hydrogenation has gained much attention and made tremendous progress. Thus, many highly efficient catalysts have been studied to discover their active sites and provide mechanistic insights. This paper summarizes recent advances in CO2 hydrogenation and its conversion into various hydrocarbons such as formate, methanol, and C2+ products. As for formate production, Au and Ru nanocatalysts show superior activity. However, considering the catalyst cost, Cu‐based catalysts have an excellent prospect for methanol production, among other catalysts. Ultra‐small nanoparticles and nanoclusters appear promising to provide highly active cost‐effective catalysts. A growing number of researchers are investigating the possibility of directly synthesizing C2+ products through CO2 hydrogenation. The major challenge in producing heavy hydrocarbons is breaking the ASF limitations, which have been achieved over bifunctional catalysts using zeolites. Using suitable support and promoter can lead to a superior activity, ascribed to structural, electronic, and chemical promotional effects.