Avalia??o do comportamento eletroqu?mico da cotinina no eletrodo de diamante dopado com boro e estudos para sua determina??o em saliva por amperometria pulsada em fluxo

Data de aprova??o ausente.A Cotinina (CO) ? o principal metab?lito da nicotina, sendo utilizada como biomarcador para monitorar a exposi??o de um indiv?duo ao tabaco. Os m?todos comumente utilizados para a determina??o desse composto em amostras biol?gicas s?o baseados na cromatografia l?quida, os quais, em geral, s?o dispendiosos e requerem tratamentos tediosos dessas amostras. Dessa maneira, torna-se necess?rio o desenvolvimento de novos m?todos mais simples e r?pidos para determina??o da CO. Nesse contexto, o presente trabalho prop?e o uso eletrodo de diamante dopado com boro (BDD) para detec??o e caracteriza??o eletroqu?mica da CO por t?cnicas voltam?tricas, bem como sua quantifica??o em amostras de saliva por meio da amperometria de m?ltiplos pulsos (MPA) em sistema de an?lise por inje??o em fluxo (FIA). Em meio de tamp?o fosfato a 0,1 mol L-1 (pH 7) a CO apresentou dois processos eletroqu?micos, um an?dico em +1,8 V e um cat?dico em -1,2 V (vs. Ag/ AgCl), sendo o segundo dependente do primeiro e ambos de car?ter irrevers?vel. Foi verificado que o processo de transporte de massas para a oxida??o da CO ? preferencialmente difusional sobre o eletrodo de BDD e que 2 el?trons e pr?tons est?o envolvidos na rea??o eletroqu?mica. O coeficiente de difus?o calculado para a CO foi de 5,7 x 10 -2 cm2 s-1. Para determina??o da CO em saliva, MPA foi utilizada aplicando-se 4 pulsos de potencial, sendo: (1) em +1,8 V/ 400 ms potencial gerador (EG) para oxida??o da CO; (2) em -1,0 V/ 500 ms potencial para elimina??o de interferentes na amostra de saliva, (3) em -1,2 V/ 30 ms potencial coletor para reduzir e quantificar a CO gerada pelo EG; (4) em -145/ 300 ms potencial para limpeza da superf?cie do BDD. A freq??ncia anal?tica te?rica foi obtida de 24 determina??es por hora com uma vaz?o otimizada em 3,0 mL min-1 e a al?a de amostragem de 300 ?L no sistema FIA. Al?m disso, um baixo desvio padr?o relativo de 1,46% foi obtido para 10 determina??es consecutivas de CO 10 ?mol L-1. Nessas condi??es, foi obtida uma faixa linear de 0,5 a 100 ?mol L-1 (R= 0,998) com limite de detec??o calculado em 0,18 ?mol L-1 para CO. Os estudos de adi??o e recupera??o da CO em amostras de saliva foram de 96,77%, Portanto, mediante a caracteriza??o eletroqu?mica e os estudos por FIA-MPA usando eletrodo de BDD, este trabalho apresenta uma alternativa simples, r?pida e de baixo custo para monitoramento do grau de exposi??o ao tabaco pela determina??o da CO em amostras de saliva.Disserta??o (Mestrado) ? Programa de P?s-gradua??o em Ci?ncias Farmac?uticas, Universidade Federal dos Vales do Jequitinhonha e Mucuri, [2016].The Cotinine (CO) is the major metabolite of the nicotine an disused as a biomarker to monitor the exposure of an individual to tobacco. The methods commonly used for CO determination in biological samples are based on liquid chromatography, which generally are expensive and require tedious treatments of the samples. Thus, it becomes necessary to develop simpler and faster methods for determining CO. In this context, this paper proposes the use boron-doped diamond (BDD) film electrode for the detection and electrochemical characterization of CO by voltammetric techniques and, CO quantification in saliva samples by multiple-pulse amperometry (MPA) in analysis by flow injection (FIA) system. In phosphate buffer solution 0.1 mol L-1 (pH 7), the CO presented two electrochemical processes, one anodic at + 1.8V and one cathode at -1.2V (vs. Ag/ AgCl), with the second process dependent on the first and both irreversible process. It was found that CO electrochemical processes are controlled by diffusion and, two-protons and two-electrons are involved in the oxidation reaction. The diffusion coefficients calculated for CO was 5.7 x 10 -2 cm2 s-1. In determination of CO in saliva samples, the MPA detection was used applying four potential pulses: (1) at +1.8V/ 400ms ? generator potential pulse (EG) for oxidation of CO; (2) at-1.0V/500ms - potential for remove possible interferents, (3) at - 1.2V/30ms - collector potential pulse potential for reduction of the product generated by EG and CO quantification; (4) at-14.5V/ 300 ms- potential pulse for cleaning BDD electrode. The proposed method obtained a theoretical analytical frequency with 24 determinations per hour by FIA system in flow rate of 3.0 ml min-1 and sample loop of 300?L. Furthermore, a low relative standard deviation of 1.46% was obtained for 10 measurements of CO 10 ?mol L-1. Under these conditions, A good linear range from 0.5 to 100 ?mol L-1 (R = 0.998) was obtained with a detection limit estimated at 0.18 ?mol L-1 for CO. The addition and recovery studies of CO in saliva samples were 96.77%. Therefore, this work presents, by the first time, an electrochemical characterization of the CO and a method simple, fast and low cost for monitoring the degree of exposure to tobacco by CO determination in saliva samples using FIA-MPA technique

Piroxicam voltammetric determination by ultra low cost pencil graphite electrode

Piroxicam (PRX) was determined in pharmaceutical capsules with differential pulse voltammetry (DPV) in a three electrode system consisting of a pencil graphite electrode (PGE) as working electrode, a Pt wire and a reference electrode of Ag/AgCl/KCl 3 M. An irreversible oxidation peak was observed in Epa c.a. 0.6 V, which correlates to the oxidation of PRX. The coefficient of linear correlation obtained was 0.9946, with limit of detection of 2.1 µM and limit of quantification of 4.7 µM. PGE assays showed good analytical performance compared to high performance liquid chromatography and spectrophotometry, showing the potential to be further developed and employed in quick and simple analyses

Electrochemical Characterization of Central Action Tricyclic Drugs by Voltammetric Techniques and Density Functional Theory Calculations

This work details the study of the redox behavior of the drugs cyclobenzaprine (CBP), amitriptyline (AMP) and nortriptyline (NOR) through voltammetric methods and computational chemistry. Results obtained in this study show that the amine moiety of each compound is more likely to undergo oxidation at 1a at Ep1a ≈ 0.69, 0.79, 0.93 V (vs. Ag/AgCl/KClsat) for CBP, AMP and NOR, respectively. Moreover, CBP presented a second peak, 2a at Ep2a ≈ 0.98 V (vs. Ag/AgCl/KClsat) at pH 7.0. Furthermore, the electronic structure calculation results corroborate the electrochemical assays regarding the HOMO energies of the lowest energy conformers of each molecule. The mechanism for each anodic process is proposed according to electroanalytical and computational chemistry findings, which show evidence that the methods herein employed may be a valuable alternative to study the redox behavior of structurally similar drugs