This work describes the development of an automatic titrometric method in flow-batch with potentiometric detection using alternative and easily accessible materials. Arduino board and its modules, solenoid valves to control the flow rate, peristaltic pump to propel and suction fluids and tubes of inert material to connect the different parts of the Flow-Batch Analyser (FBA) were used. The use of solenoid valves controlled by microcontrollers proved to be efficient for controlling the flow in FBA systems, the correlations of their flow rates as a function of time showed good linearity with correlation coefficients (r) 0.9994 and 0.9997 for the valve 1 and valve 2, respectively, allowing correct addition of pre-established volumes. Accuracy was verified by comparing the results of the proposed method with the classic potentiometric titration with statistically evaluated by Student’s t-test in NaOH with HCl and vinegar with NaOH titrations. Results confirmed the efficiency to use Arduino board and its modules and automatic titrometric method in flow-batch developed in this work allow the implementation of practical disciplines, such as potentiometric titration and flow analysis system in undergraduate courses, making these instruments more accessible, especially for the chemistry students.

Two new compounds, caryopristimerin and 2α,3α,22β-trihydroxy-21-oxo-29-nor-friedelan-24-oic acid, were isolated from the hexane/ethyl ether extract of Salacia crassifolia roots. Caryopristimerin represents the first example of a homo Diels-Alder adduct of a sesquiterpene and a triterpene, and the new 29-nor-friedelane displays a highly oxygenated A ring with a carboxylic group at the unusual C-5 position. The new compounds were elucidated by infrared (IR), high-resolution-atmospheric pressure chemical ionization-mass spectrometry (HR-APCI-MS), 1D/2D nuclear magnetic resonance (NMR) and single crystal X-ray diffraction analysis. Additionally, the known compounds 3-oxo-29-hydroxyfriedelane, pristimerin, tingenone and netzahualcoyonol are herein reported for the first time as constituents of S. crassifolia. Their structures were established by spectroscopic analysis.

Um eletrodo compósito sólido à base de grafite e resina poliuretana modificado com um complexo de base de Schiff do tipo tetradentada simétrica, N, N'-bis(salicilideno)etilenodiamino de cobre(II) ([Cu(II)Salen)]), foi avaliado como sensor bio-inspirado, usando dopamina (DA) como sonda eletroquímica. O comportamento voltamétrico do modificador [Cu(II)Salen] foi avaliado em eletrodo de pasta de carbono modificado e um mecanismo redox foi proposto. As potencialidades analíticas do eletrodo compósito à base de grafite e resina poliuretana (GPU) modificado com [Cu(II Salen] (MGPU) foram avaliadas usando DA. O eletrodo MGPU apresentou melhores resultados quando comparado ao GPU sem modificação, exibindo efeito eletrocatalítico, o que o caracteriza como sensor bio-inspirado. O eletrodo MGPU foi aplicado na determinação de DA em formulações farmacêuticas utilizando DPV e o resultado foi comparado àquele obtido com o método oficial (cromatografia líquida de alta eficiência, HPLC), descrito na farmacopeia americana, concordando em um nível de 95% de confiança de acordo com o teste t-student.

A solid composite electrode based on graphite and polyurethane resin modified with a copper(II) complex of the symmetrical tetradentate Schiff's base type, N, N'-ethylenebis(salicylideneiminato) copper(II) ([Cu(II)Salen]), was evaluated as a bio-inspired sensor using dopamine (DA) as a model analyte. The voltammetric behavior of the modifier [Cu(II)Salen] was investigated at a modified carbon paste electrode and a redox mechanism was proposed. The analytical potentialities of the composite electrode based on graphite and polyurethane resin (GPU) modified with [Cu(II)Salen] (MGPU) were evaluated using DA as probe. MGPU presents best results when compared with GPU without modification, with electrocatalytic effect, indicating that the electrode can be characterized as a bio-inspired sensor. The MGPU electrode was applied in the determination of DA in pharmaceutical formulation using DPV and the results were compared to those obtained with the official method (high performance liquid chromatography, HPLC) as described in US Pharmacopoeia, agreeing within 95% confidence level according to student's t-test.

O uso de um eletrodo compósito à base de grafite de borracha de silicone (GSR) na determinação de rutina, (vitamina P), por voltametria de pulso diferencial, é descrito. Voltamogramas cíclicos da rutina apresentaram um par de picos de oxidação/redução no GSR em 0,411 e 0,390 V (vs. ECS), respectivamente, em solução tampão Britton-Robinson (B-R) pH 4,0. Em voltametria de pulso diferencial (DPV), após a otimização das condições, o pico de oxidação em 0,370 V (vs. ECS) foi usado na determinação quantitativa de rutina. Neste caso, um intervalo linear entre 5,0-50,0×10-8 mol L-1 foi observado com um limite de detecção de 1,8×10-8 mol L-1. Recuperações de 94 a 113% foram observadas. A superfície do eletrodo foi renovada por polimento, com uma repetibilidade de 1,09 ± 0,06 µA (n = 10) para a corrente de pico. A rutina foi determinada em uma formulação farmacêutica e os resultados concordaram com aqueles obtidos de um método oficial com 95% de confiança.

The possibility of using a graphite silicone-rubber composite electrode (GSR) in a differential pulse voltammetric(DPV) procedure for rutin (vitamin P) determination is described. Cyclic voltammograms of rutin presented a reversible pair of oxidation/reduction peaks respectively at 0.411 and 0.390 V (vs. SCE) at the GSR surface in Britton-Robinson(B-R) buffer solution pH 4.0. In DPV after optimization of conditions, an oxidation peak at 0.370 V (vs. SCE) was used to quantitative determination of rutin in B-R buffer solution pH 4.0. In this case a linear dynamic range of 5.0×10-8 to 50.0×10-8 mol L-1 was observed with a detection limit of 1.8×10-8 mol L-1 for the analyte. Recoveries from 94 to 113% were observed. The electrode surface was renewed by polishing after each determination, with a repeatability of 1.09 ± 0.06 µA (n = 10) peak current. Rutin was determined in a pharmaceutical formulation using the proposed electrode and the results agreed with those from an official method within 95% confidence level.