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A new method using differential pulse adsorptive stripping voltammetry for the determination of atrazine (ATZ) in natural water samples using a bismuth film electrode (BiFE) is proposed. The calibration curve was linear in the atrazine concentration range from 6.7 10 À7 to 2.0 10 À5 mol L À1 , with a limit of detection (LOD) of 1.4 10 À7 mol L À1. The proposed electrode was applied for atrazine determination with satisfactory results compared with a high-performance liquid chromatography method (HPLC).

In this research, a boron-doped diamond (BDD) electrode has been explored to detect the chloroquine drug. The electrochemical performance of BDD electrode towards the irreversible anodic response of chloroquine was investigated by subjecting this electrode to the cathodic (−0.5 A cm−2 by 180 s, generating a predominantly hydrogen-terminated surface) and anodic (+0.5 A cm−2 by 30 s, oxygen-terminated surface) pretreatments. The cathodically pretreated BDD electrode ensured a better-defined anodic peak and higher current intensity. Thus, by applying the cathodically pretreated BDD electrode and square-wave voltammetry (SWV), the analytical curve was linear from 0.01 to 0.25 µmol L−1 (correlation coefficient of 0.994), with sensitivity and limit of detection of 12.2 µA L µmol−1 and 2.0 nmol−1, respectively. This nanomolar limit of detection is the lowest recorded so far with modified and unmodified electrodes.

Silver materials are known to present excellent properties, such as high electrical and thermal conductivity as well as chemical stability. Silver-based inks have drawn a lot of attention for being compatible with various substrates, which can be used in the production uniform and stable pseudo-reference electrodes with low curing temperatures. Furthermore, the interest in the use of disposable electrodes has been increasing due to the low cost and the possibility of their use in point-of-care and point-of-need situations. Thus, in this work, two new inks were developed using Ag as conductive material and colorless polymers (nail polish (NP) and shellac (SL)), and applied to different substrates (screen-printed electrodes, acetate sheets, and 3D-printed electrodes) to verify the performance of the proposed inks. Measurements attained with open circuit potential (OCP) attested to the stability of the potential of the pseudo-reference proposed for 1 h. Analytical curves for β-estradiol were also obtained using the devices prepared with the proposed inks as pseudo-references electrodes, which presented satisfactory results concerning the potential stability (RSD < 2.6%). These inks are simple to prepare and present great alternatives for the development of pseudo-reference electrodes useful in the construction of disposable electrochemical systems.

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____________________________________________________________________________Resumo: O presente trabalho descreve um método quimiluminescente de análise por injeção em fluxo envolvendo multicomutação, para a determinação de rutina em formulações farmacêuticas. O método é baseado na oxidação da rutina pelo hipoclorito de sódio, a qual promove o decréscimo da magnitude do sinal quimiluminescente, se comparado à reação na ausência de rutina. Sob condições otimizadas, foi obtida uma curva analítica para concentrações de rutina variando de 5.0 × 10 -6 mol L -1 a 1.0 × 10 -4 mol L -1 (r = 0,996) com um limite de detecção de 9.7 × 10 -7 mol L -1 e uma frequência de amostragem de 120 h -1. Estudos de repetibilidade para uma concentração de rutina de 7,0 x 10 -6 mol L -1 apresentaram um desvio padrão relativo (DPR) menor que 5,0% para 10 determinações consecutivas. O método proposto foi aplicado com sucesso na determinação de rutina em formulações farmacêuticas. Palavras-chave:Análise por injeção em fluxo, Rutina, Quimiluminescência, Multicomutação ____________________________________________________________________________ Abstract: This paper reports a flow injection chemiluminescence method involving multicommutation for rutin determination in pharmaceutical formulations. The method is based on the oxidation of rutin by sodium hypochlorite which decreases the signal magnitude when compared with the same reaction without the rutin. Under optimized conditions, an analytical curve was obtained for rutin concentration range from 5.0 × 10 -6 mol L -1 to 1.0 × 10 -4 mol L -1 (r = 0.9966) with detection limit of 9.7 × 10 -7 mol L -1 and a sampling frequency of 120 h -1 . Repeatability study for a 7.0 × 10 -6 mol L -1 rutine concentration showed a relative standard deviation (RSD) less than 5.0% for ten consecutives determination. The proposed method was applied successfully for rutin determination in pharmaceutical products.