Diclofenac on Boron-Doped Diamond Electrode: From Electroanalytical Determination to Prediction of the Electrooxidation Mechanism with HPLC-ESI/HRMS and Computational Simulations

Autor(es)

Lucas, Francisco Willian de S. ^{[1, 2]} ; Mascaro, Lucia H. ^[1] ; Fill, Taicia P. ^[1] ; Rodrigues-Filho, Edson ^[1] ; Franco-Junior, Edison ^[3] ; Homem-de-Mello, Paula ^[3] ; de Lima-Neto, Pedro ^[2] ; Correia, Adriana N. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP - Brazil

^[2] Univ Fed Ceara, Ctr Ciencias, Dept Quim Analit & Fis Quim, BR-60440900 Fortaleza, Ceara - Brazil

^[3] Univ Fed ABC, Ctr Ciencias Nat & Humanas, BR-09210580 Santo Andre, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Langmuir; v. 30, n. 19, p. 5645-5654, MAY 20 2014.
• Citações Web of Science: 17

Resumo

Using square-wave voltammetry coupled to the boron-doped diamond electrode (BDDE), it was possible to develop an analytical methodology for identification and quantification of diclofenac (DCL) in tablets and synthetic urine. The electroanalytical procedure was validated, with results being statistically equal to those obtained by chromatographic standard method, showing linear range of 4.94 X 10(-7) to 4.43 X 10(-6) mol L-1, detection limit of 1.15 X 10(-7) mol L-1, quantification limit of 3.85 x 10(-7) mol L-1, repeatability of 3.05% (n = 10), and reproducibility of 1.27% (n = 5). The association of electrochemical techniques with UV-vis spectroscopy, computational simulations and HPLC-ESI/HRMS led us to conclude that the electrooxidation of DCL on the BDDE involved two electrons and two protons, where the products are colorful and easily hydrolyzable dimers. Density functional theory calculations allowed to evaluate the stability of dimers A, B, and C, suggesting dimer C was more stable than the other two proposed structures, ca. 4 kcal mol(-1). The comparison of the dimers stabilities with the stabilities of the molecular ions observed in the MS, the compounds that showed retention time (RT) of 15.53, 21.44, and 22.39 min were identified as the dimers B, C, and A, respectively. Corroborating the observed chromatographic profile, dimer B had a dipole moment almost twice higher than that of dimers A and C. As expected, dimer B has really shorter RT than dimers A and C. The majority dimer was the A (71%) and the C (19.8%) should be the minority dimer. However, the minority was the dimer B, which was formed in the proportion of 9.2%. This inversion between the formation proportion of dimer B and dimer C can be explained by preferential conformation of the intermediaries (cation-radicals) on the surface. (AU)

• Processo FAPESP: 12/10947-2 - Obtenção e caracterização de filmes finos de calcogenetos do tipo MBS (M = Ag ou Cu; B = In, Ga, Sb ou Tl; e S = S ou Se ) para aplicação em células fotovoltaicas
• Beneficiário: Francisco Willian de Souza Lucas
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 12/20653-6 - Modelos computacionais para o estudo do espectro de emissão de corantes sob a influência de nanopartículas metálicas
• Beneficiário: Edison Franco Junior
• Modalidade de apoio: Bolsas no Brasil - Doutorado