This work describes the development of a platform based on bismuth oxyiodide (BiOI), sulfur-doped graphitic carbon nitride (S-g-C3N4), and bismuth-doped sodium tantalate perovskite (Bi-NaTaO3) for zero-biased photoelectrochemical immunosensing of cardiac troponin I (cTnI) biomarker. The spectroscopic, structural, morphological, and compositional characteristics of the photoelectrochemical (PEC) materials were evaluated by Raman and Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Electrochemical impedance (EI) measurements were performed under the incidence and absence of light to investigate the effects of photons on the charge transfer resistance of the photoelectrochemical platform. The influence of the cTnI biomarker on the photoelectrochemical response of the anti-cTnI antibody-modified photoelectrochemical platform (anti-cTnI/BiOI/S-g-C3N/Bi-NaTaO3/FTO) was evaluated by measuring the photocurrent of the system. The immunosensor presented a linear response range from 1 pg mL 1 to 50 ng mL 1, mean recovery percentage between 95.98 and 99.78% in real human serum samples, and selectivity for the cTnI biomarker.

This work describes the development of a photoelectrochemical sensor for glucose quantification exploiting a light assisted-batch injection analysis (BIA) cell. A light-emitting diode (LED) lamp was employed to control the incidence of light on the p-Cu2O/n-Cu2O/fluorine-doped tin oxide (FTO) photoactive platform in BIA cell. The p-Cu2O/n-Cu2O/FTO platform was constructed by electrodepositing n-Cu2O and p-Cu2O and the characteristics of electrodeposited Cu2O films were investigated by X-ray diffraction (XRD), Raman spectroscopy, and electrochemical impedance spectroscopy. The light assisted-batch injection analysis of glucose based on the illuminated p-Cu2O/n-Cu2O/FTO photoelectrode presented a linear response of 10 μmol L-1-1 mmol L-1, a limit of detection of 4.0 μmol L-1, and sensitivity of 0.768 ± 0.011 μA L μmol-1 cm-2. The system presented an average recovery value of 96% when applied to the determination of glucose in an artificial saliva sample, which indicates that the incidence of light on photoelectroactive platforms is a promising approach for the determination and quantification of glucose.

This work presents a simple and fast method for colchicine (CO) determination in pharmaceutical formulations and urine by multiple pulse amperometry (MPA) with flow injection analysis (FIA) system using a boron-doped diamond electrode. In optimized conditions, it was possible to quantify CO in urine samples without interference of uric acid and ascorbic acid. The working linear range for CO quantification was achieved from 1.0 × 10-7 to 0.5 × 10-3mol L-1 with a low limit of detection of 2.14 × 10-8mol L-1. Furthermore, the proposed method showed high repeatability for 10 consecutive injections of 1.0 × 10-4mol L-1 CO (relative standard deviation = 1.28%) and good analytical frequency (30 determinations per hour). The addition and recovery studies in all pharmaceutical samples were approximately 100% and the results for CO determination were compared by high performance liquid chromatography (HPLC) with UV detection.

In this study, a photoelectroanalytical sensor for determination of adrenaline based on deoxyribonucleic acid (DNA) and anatase titanium dioxide (TiO2) nanoparticles sensitized with bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) was developed, which we henceforward call BEDT-TTF/DNA/TiO2/ITO. The photoelectroanalytical sensor showed high photocurrent to adrenaline under visible light emitting diode (LED) light irradiation in comparison to each component of the composite material. Under optimized conditions, the BEDT-TTF/DNA/TiO2/ITO sensor shows a linear response range from 10 nmol L-1 up to 100 µmol L-1 with a sensitivity of 8.1 nA L µmol-1 and limit of detection of 1 nmol L-1 for the detection of adrenaline. The photoelectrochemical sensor showed high photocurrent to adrenaline in comparison to photocurrent response to ascorbic acid and uric acid. The BEDT-TTF/DNA/TiO2/ITO photoelectrochemical sensor was successfully applied to urine samples, with recovery values between 96 and 106%.

The present work describes the development of a selective electrochemical sensor for urate based on tris(1,10-phenantroline)copper(II) bis(tetracyanoquinodimethanide) (Cu(phen)3(TCNQ)2) adsorbed on multi-walled carbon nanotubes (CNT). The composite material was characterized by infrared spectroscopy, scanning electron microscopy, and electrochemical impedance spectroscopy. The composite material showed an excellent electrocatalytic activity toward oxidation of urate. The heterogeneous charge transfer rate constant (k’) between the analyte and the sensor was determined using linear sweep voltammetry experiments. The composite material shows a linear range from 5 up to 2500 µmol L-1 with limit of detection of 1.05 µmol L-1 and limit of quantification of 3.50 µmol L-1. The high sensitivity and selectivity of the sensor for urate was sufficient for its determination in biological fluids. Finally, the proposed sensor was successfully applied in urine samples.

O presente trabalho apresenta uma metodologia simples, rápida e de baixo custo para a determinação de citrato de sildenafila (SC) em formulações farmacêuticas de referência (Viagra®) e em produtos similares, genéricos e manipulados, por amperometria de múltiplos pulsos em sistema FIA (análise por injeção em fluxo). O método consiste na aplicação de três pulsos de potencial (sequenciais) em função do tempo sobre um eletrodo de trabalho de diamante dopado com boro. SC foi detectado em 1,6 e 1,9 V por meio de dois diferentes processos irreversíveis de oxidação. Um terceiro pulso de potencial (1,0 V) foi aplicado para regeneração da superfície do eletrodo. Foram obtidos limites de detecção na ordem de 10 nmol L-1 e desvio padrão relativo menor que 0,2% (n = 10) para SC 4,5 X 10-5 mol L-1, permitindo 86 injeções por hora. Estudos de adição e recuperação nas amostras ficaram próximos de 100% e os resultados foram validados por cromatografia.

This work presents a simple, fast and low-cost method for determining sildenafil citrate (SC) in Viagra® and in similar, generic and manipulated pharmaceutical formulations using flow injection analysis (FIA) with multiple pulse amperometric detection. The method consists on the application of three sequential potential pulses as a function of time. SC is detected at 1.6 and 1.9 V by two different irreversible oxidation processes. The third potential pulse (1.0 V) is applied for the regeneration (cleaning) of the surface of the boron-doped electrode. The limit of detection on an order of 10 nmol L-1 was reached with a relative standard deviation of less than 0.2% (n = 10) for 4.5 X 10-5 mol L-1 CS. The analytical frequency was calculated in 86 injections per hour. The addition recovery studies in all the samples were approximately 100% and the results were validated by chromatographic methods.