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Even though ammonia is a natural component of aquatic environments, elevated concentrations indicate pollution and environmental degradation. Consequently, efficient analytical methods for monitoring ammonia levels are crucial for preserving water quality. Voltammetry offers a sustainable approach for NH3 quantification, combining good analytical performance with low sample and reagent consumption, minimizing waste generation. However, despite these advantages, the voltammetric determination of ammonia remains relatively unexplored. Therefore, this study investigated the electrochemical behavior of NH3 in alkaline solutions using a non-modified Pt electrode and evaluated the performance of differential pulse voltammetry (DPV) and square wave voltammetry (SWV) for NH3 determination. DPV provided superior performance, with limits of detection and quantification of 0.79 µmol L-1 (0.011 ppmN) and 2.6 µmol L-1 (0.036 ppmN), respectively, which comply with the maximum allowable ammonia concentration in natural waters according to Brazilian and European regulations. The voltammetric method successfully quantified ammonia in tap and river water samples, providing results concordant with the established Berthelot spectrophotometric method, at a 95% confidence level. Additionally, it is simple and fully accessible to non-electrochemist since no sophisticated procedures for electrode modification are needed. Finally, the high analytical performance of the proposed method makes it valuable for pollution monitoring in aquatic environments.

Many adults with phenylketonuria (PKU) rely on medical nutrition therapy (MNT; low phenylalanine (Phe) diet with protein substitutes/medical foods) to maintain blood Phe concentrations within recommended ranges and prevent PKU-associated comorbidities. Despite disease detection through newborn screening and introduction of MNT as early as birth, adherence to MNT often deteriorates from childhood onwards, complicating the assessment of its effectiveness in the long term. Via a modified Delphi process, consensus (≥70% agreement) was sought on 19 statements among an international, multidisciplinary 13-member expert panel. After three iterative voting rounds, the panel achieved consensus on 17 statements related to the limitations of the long-term effectiveness of MNT (7), the burden of long-term reliance on MNT (4), and its potential long-term detrimental health effects (6). According to the expert panel, the effectiveness of MNT is limited in the long term, is associated with a high treatment burden, and demonstrates that adults with PKU are often unable to achieve metabolic control through dietary management alone, creating an unmet need in the adult PKU population.

Um método envolvendo a pré-concentração e redissolução anódica em condições de voltametria de pulso diferencial empregando um eletrodo de pasta de carbono modificado (EPCM) com uma resina de troca iônica Amberlite IR120 foi proposto para a determinação de íons chumbo em álcool combustível. O procedimento é baseado em um pico de oxidação do analito observado em -0,53 V(vs. Ag/AgCl) em solução de HCl. As melhores condições experimentais encontradas foram: 5% (m/m) da Amberlite IR120 para a construção do eletrodo, solução de HCl 0,1 mol L -1 , velocidade de varredura de 10 mVs -1 , tempo de pré-concentração de 15 min e amplitude de pulso de 100 mV. Utilizando essas condições, o EPCM apresentou uma resposta linear entre a corrente de pico anódica e a concentração de íons chumbo para o intervalo entre 9,9 x 10 -9 e 1,2 x 10 -6 mol L -1 e um limite de detecção de 7,2 x 10 -9 mol L -1 . Valores de recuperação entre 96 % e 102 % foram encontrados para amostras de álcool combustível enriquecidas com Pb 2+ em níveis de 10 -7 mol L -1 . O efeito da pre

This paper describes a comparative study between the procedures of deconvolution and the second-order derivative of square wave voltammograms to achieve separation of the voltammetric peaks of levofloxacin (LEVO) and norfloxacin (NOR), for their simultaneous quantification in urine samples. The obtained results indicate that the use of second-derivative voltammograms coupled with carbon screen-printed electrodes is the most efficient approach for completely separating the voltammetric peaks of LEVO and NOR. In addition, this approach has produced detection limits lower than 1.0 µmol L-1 and a wide linear range for both drugs. The proposed method was successfully used to simultaneously determine LEVO and NOR in spiked human and bovine urine samples with recovery percentages close to 100% for all analyzed samples.

In this work, a voltammetric method for determination of nitrite in tap and mineral waters samples was developed. The method is based on the reduction of nitrite catalyzed by the electrochemical mediator [Fe(CN)6]3-. A carbon paste electrode (CPE) prepared with solid paraffin as binder agent was used as working electrode and cyclic voltammetry was the voltammetric technique employed for nitrite quantification. All parameters of the analytical method were optimized and the best conditions obtained were: BR buffer 0.04 mol L-1 pH = 1.0 as supporting electrolyte and 0.7 mmol L-1 of Fe(CN)6] 3- in the electrochemical cell. Under these optimized conditions, the method presented a linear range from 0.05 to 2.5 mmol L-1 of nitrite, with limits of detection and quantification equal to 22 and 75 μmol L-1, respectively. Spiked samples of mineral and tap water were analyzed by the proposed method and recovery percentages close to 100 % were obtained for all analyzed samples. Moreover, the method has presented a satisfactory precision since low values of relative standard deviation (RSD) were always obtained. These results indicate that the method allow the reliable determination of nitrite in water samples in a simple and inexpensive way. DOI: http://dx.doi.org/10.17807/orbital.v7i1.679

In this work, bismuth films were electrodeposited in situ onto carbon paste electrodes (CPEs) and they were used for lead determination in tap water samples by anodic stripping square wave voltammetry. The analytical performance of CPEs prepared with different binder agents was compared. It was observed that CPEs prepared with solid paraffin as binder agent provided the best results. All parameters of the analytical method were optimized and the best conditions obtained were: acetate buffer 0.1 mol L-1 (pH=4.75) as supporting electrolyte; pre-concentration time of 240 s and electrodepositing potential of -1.2 V vs. Ag/AgCl/KClsat. The best Bi3+ concentration was 2.0 μmol L-1. At these optimized conditions, analytical curves were constructed and two linear regions were obtained: 25 to 100 nmol L-1 and 250 to 1000 nmol L-1. Detection limits (LD) corresponding to these linear ranges were, respectively, 5.77 and 52.3 nmol L-1. Recovery experiments were performed in tap water samples and recovery percentages close to 100 % were always obtained although the best results were obtained for samples spiked with 250 nmol L-1 of Pb2+.

This work describes a simple and inexpensive flow injection analysis system in which gravity force provides fluid propulsion while needles for insulin administration or metallic wires act as electrodes for amperometric detection. The proposed system was able to demonstrate the influence of several operational parameters on the transient signals. Moreover, this system was successfully used to evaluate both the stoichiometry of Cu2+-EDTA complex and the effect of pH on the kinetics of the reaction between ferricyanide and ascorbic acid. Therefore, the proposed system can be regarded as an efficient and accessible didactic tool for the teaching of FIA principles.