TiO2/MWCNT/Nafion-Modified Glassy Carbon Electrode as a Sensitive Voltammetric Sensor for the Determination of Hydrogen Peroxide.

In this work we describe a straightforward approach for creating a nanocomposite comprising multiwalled carbon nanotubes (MWCNTs) and titanium dioxide (TiO2) using the hydrothermal technique, which is then characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDS), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) to assess its properties. Nafion is employed as a reticular agent for the nanocomposite on the glassy carbon electrode (GCE), creating the MWCNT/TiO2/Nafion/GCE system. The electrochemical behavior of the system was evaluated using cyclic voltammetry, revealing its remarkable electrocatalytic activity for detecting hydrogen peroxide in water. The developed sensor showcased a broad linear response range of 14.00 to 120.00 µM, with a low detection limit of 4.00 µM. This electrochemical sensor provides a simple and highly sensitive method for detecting hydrogen peroxide in aqueous solutions and shows promising potential for various real-world applications, particularly in H2O2 monitoring.

Evaluation of different approaches to applying the standard additions calibration method.

The extrapolation approach, traditionally used with standard additions (SA), is compared with the alternative strategies of interpolation, reversed-axis, and normalization. The interpolation approach is based on employing twice the analytical signal recorded for the sample (ysam) to determine an unknown analyte concentration. In the reversed-axis strategy, x- and y-axes are swapped when building the SA calibration plot to facilitate uncertainty estimation. A new strategy, based on signal normalization using ysam, is also described and compared to the other approaches. Results from 3 instrumental methods, 396 sample replicates, 16 analytes, and 2 certified reference materials are included in this study. For most applications, all four SA approaches provide statistically similar trueness and precision. However, extrapolation and reversed-axis provide more consistent values (within narrower ranges) than the other strategies when employing inductively coupled plasma optical emission spectrometry (ICP OES). On the other hand, normalization provides better trueness for the less robust method of microwave-induced plasma OES (MIP OES), as it is capable of minimizing systematic errors associated with different points of the calibration curve. Normalization is particularly useful for quickly processing data, without the need for inspecting each individual calibration plot to identify outlying points. Reversed-axis and normalization are the most adequate approaches for SA applications involving MIP OES and ICP-based methods. In addition to providing similar accuracies to the traditional extrapolation approach, these strategies present the advantage of a simple uncertainty estimation, which can be easily calculated using commonly available software such as Microsoft Excel and R.

Nano-encapsulated Cu(II) complex as a promising insecticidal for Aedes aegypti (Diptera: Culicidae).

Nanoparticle (NP) research is an area of scientific interest with high potential for application in biomedical, optical, and electronic fields. Due to their relatively large surface area compared to their mass, NPs can be more chemically reactive and change their reactive strength or other properties. NP-based drug delivery systems provide transport and an effective and controlled way to release the drugs. This work aimed to study the solubility and biological activity of nano-encapsulated copper metal complexes for the induction of toxicity and mortality in larvae of Aedes aegypti mosquitoes. After the nano-encapsulated metal complexes were prepared, the efficiency of this incorporation was determined by electron paramagnetic resonance, and toxicity bioassays were performed. The polymeric-based PLGA NPs encapsulating metal complexes exhibited high toxicity and specificity for target organisms (insect vectors, i.e., A. aegypti), with relatively less environmental impact and long-term control of their breeding.

Multi-electrode platform for selective electrochemical sensing: 3D-printed insulating plastic is turned into a five-electrodes chip.

We report a method to turn a 3D-printed plastic piece into a five-electrodes chip for multiple analytes detection. A chip containing Pd, Ni, and Ru working electrodes is used to sense hydroquinone, acetaminophen, salicylic acid, and hydroxychloroquine at once. The analysis is sequentially achieved simply by changing the proper electrode connection, without changing mobile parts, neither adding reactants, nor electrolytes. This strategy is an alternative for low-cost selective electrochemical detection.

Simultaneous quantification of seven multi-class organic molecules by single-shot dilution differential pulse voltammetric calibration.

The contamination of water sources by anthropogenic activities is a topic of growing interest in the scientific community. Therefore, robust analytical techniques for the determination and quantification of multiple substances are needed, which often require complex and time-consuming procedures. In this context, we describe a univariate calibration method to determine emerging multi-class contaminants in different water sources. The instrumental setup is composed of a lab-made glass electrochemical cell with three electrodes: Pt counter, Ag/AgCl reference, and BDD working electrodes. With this system, we were able to simultaneously quantify tert-butylhydroquinone, acetaminophen, estrone, sulfamethoxazole, enrofloxacin, caffeine, and ibuprofen by differential pulse voltammetry. Only two calibration solutions are required for the Single-shot Dilution Differential Pulse Voltammetric Calibration (SSD-DP-VC) method described here, which can significantly improve sample throughput. Two robust univariate calibration strategies were also applied and compared with SSD-DP-VC. The new method is simple, fast, and comparable with traditional calibration methods, showing similar precision and accuracy for all determinations evaluated.

Simultaneous separation and electroanalysis in a single polydimethylsiloxane-based platform.

Channel-based microfluidic devices integrating the separation step and detection system are key factors to expand microanalysis application. However, these devices still depend on macroscale external equipment for pre-treatment of the sample, separation, or detection. The integration of all steps in only one stage is critical to improving feasibility. Herein, we use a low-cost protocol to solve part of the challenge by designing a dual-mode system onto single polydimethylsiloxane (PDMS)-based platform - overall dimensions of 65 mm length × 20 mm width × 14 mm height and the inner diameter of 297±10 µm height × 605±19 µm width - for column-free separation and simultaneous detection. As a proof-of-concept, we used this all-in-one PDMS platform to separate - without the packet-based phase - and determine salicylic acid (SA) and caffeine (CAF) with a detection limit of 0.20 and 0.18 µmol L-1 and quantification limit of 0.70 and 0.60 µmol L-1 for SA and CAF, respectively. We separated the mixture using forced convection into a chemically treated microchannel while detecting the analytes in amperometric mode. Here, we report new insights into how integrating analytes separation and further electroanalysis into a single miniaturized device.

Effective killing of bacteria under blue-light irradiation promoted by green synthesized silver nanoparticles loaded on reduced graphene oxide sheets.

Graphene oxide (GO) materials loaded with silver nanoparticles (AgNPs) have drawn considerable attention due to their capacity to efficiently inactivate bacteria though a multifaceted mechanism of action, as well as for presenting a synergetic effect against bacteria when compared to the activity of AgNPs and GO alone. In this investigation, we present an inexpensive and environmentally-friendly method for synthesizing reduced GO sheets coated with silver nanoparticles (AgNPs/r-GO) using a coffee extract solution as a green reducing agent. The physical and chemical properties of the produced materials were extensively characterized by scanning electron microscopy (SEM), field-emission gun transmission electron microscopy (FEG-TEM), ultraviolet and visible absorption (UV-Vis), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and ion release determination. The results demonstrated that AgNPs/r-GO composites were successfully produced, revealing the formation of micrometer-sized r-GO sheets decorated by AgNPs of approximately 70 nm diameter. Finally, bactericidal and photobactericidal effects of the AgNPs/r-GO composites were tested against Staphylococcus aureus, in which the results showed that the composites presented antimicrobial and photoantimicrobial activities. Moreover, our results demonstrated for the first time, to our knowledge, that an efficient process of bacterial inactivation can be achieved by using AgNPs/r-GO composites under blue light irradiation as a result of three different bacterial killing processes: (i) chemical effect promoted by Ag+ ion release from AgNPs; (ii) photocatalytic activity induced by AgNPs/r-GO composites, enhancing the bacterial photoinactivation due to the excited-Plasmons of the AgNPs when anchored on r-GO; and (iii) photodynamic effect produced by bacterial endogenous photosensitizers under blue-light irradiation. In summary, the present findings demonstrated that AgNPs/r-GO can be obtained by a non-toxic procedure with great potential for biomedical-related applications.

Evaluating the applicability of multi-energy calibration as an alternative method for quantitative molecular spectroscopy analysis.

Multi-Energy Calibration (MEC) was recently proposed as an innovative analytical method to be used in efficient and accurate quantitative analysis based on atomic spectroscopy. Here, the applicability of the MEC method for quantifying molecular species using UV-Vis and fluorescence measurements was evaluated for the first time. UV-Vis and fluorescence spectra of the analytical solutions of methylene blue and eosin-methylene blue in two different solvents (distilled-deionized water and methanol) were collected. MEC showed high precision and sensitivity for determining the analyte concentration, providing similar limit of detection and quantification when compared with conventional analytical methods, such as external standard calibration and standard additions. Therefore, the present study has shown that MEC can be successfully applied for quantifying molecular species in a simple and efficient way accounting UV-Vis and fluorescence spectroscopy.

Cytotoxic and genotoxic effects of silver nanoparticles on meristematic cells of Allium cepa roots: A close analysis of particle size dependence.

The use of silver nanoparticles (AgNPs) in commercial products has increased significantly in recent years. However, findings on the toxic effects of the AgNPs are still limited. This paper reports an investigation on the cytotoxic and genotoxic potential of the AgNPs on root cells of Allium cepa. Germination (GI), root elongation (REI), mitotic (MI), nuclear abnormality (NAI), and micronucleus index (MNI) were determined for seeds exposed to various AgNPs diameters (10, 20, 51, and 73 nm) as well as to the silver bulk (AgBulk) (micrometer-size particles) at the concentration of 100 mg·L-1. Transmission electron microscopy (TEM) provided the particle size distribution, while dynamic light scattering (DLS) was used to get the hydrodynamic size, polydispersity index, and zeta potential of the AgNPs. Laser-induced breakdown spectroscopy (LIBS) and inductively coupled plasma/optical emission spectrometry (ICP OES) were applied for quantifying the AgNPs content uptake by roots. Silver dissolution was determined by dialysis experiment. Results showed that the AgNPs penetrated the roots, affecting MI, GI, NAI, and MNI in meristematic cells. Changes in these indicators were AgNPs diameter-dependent so that cytotoxic and genotoxic effects in Allium cepa increased with the reduction of the particle diameter. The results also revealed that the AgNPs were the main responsible for the cytotoxicity and genotoxicity since negligible silver dissolution was observed.

Multi-energy calibration applied to atomic spectrometry.

Multi-energy calibration (MEC) is a novel strategy that explores the capacity of several analytes of generating analytical signals at many different wavelengths (transition energies). Contrasting with traditional methods, which employ a fixed transition energy and different analyte concentrations to build a calibration plot, MEC uses a fixed analyte concentration and multiple transition energies for calibration. Only two calibration solutions are required in combination with the MEC method. Solution 1 is composed of 50% v v-1 sample and 50% v v-1 of a standard solution containing the analytes. Solution 2 has 50% v v-1 sample and 50% v v-1 blank. Calibration is performed by running each solution separately and monitoring the instrument response at several wavelengths for each analyte. Analytical signals from solutions 1 and 2 are plotted on the x-axis and y-axis, respectively, and the analyte concentration in the sample is calculated from the slope of the resulting calibration curve. The method has been applied to three different atomic spectrometric techniques (ICP OES, MIP OES and HR-CS FAAS). Six analytes were determined in complex samples (e.g. green tea, cola soft drink, cough medicine, soy sauce, and red wine), and the results were comparable with, and in several cases more accurate than, values obtained using the traditional external calibration, internal standardization, and standard additions methods. MEC is a simple, fast and efficient matrix-matching calibration method. It may be applied to any technique capable of simultaneous or fast sequential monitoring of multiple analytical signals.

Microwave-Induced Plasma Optical Emission Spectrometry (MIP OES) and Standard Dilution Analysis to Determine Trace Elements in Pharmaceutical Samples.

In this work, we evaluate the application of microwave-induced plasma optical emission spectrometry (MIP OES) to determine of Al, Cr, Co, Cu, Fe, Mn, Ni and Zn in children's cough syrup, eye drops, and oral antiseptic using standard dilution analysis (SDA). The SDA method is simple, with only two calibration solutions prepared per sample. The first solution (S1), composed of 50% sample +50% of a standard solution, is introduced into the plasma and the analytical signals are monitored in a time-resolved fashion. Then, the second solution (S2), composed of 50% sample +50% blank, is poured into the vial containing S1. As the solutions mix, the analytical signals gradually drop to a stable baseline. The calibration curve is computed by plotting the ratio of the analyte signal (SA) over the internal standard signal (which is also part of S1) (SIS) on the y-axis, versus the inverse of the IS concentration on the x-axis (i.e., SA/SIS versus 1/CIS). In this study, SDA results were compared with values obtained with the traditional methods of external calibration (EC), internal standardization (IS), and standard additions (SA) in MIP OES determinations. The precision (represented as percent RSD) for SDA showed values in the range of 2.50-8.00% for all samples, while conventional calibration methods showed RSDs in the range of 6.40-32.50% for EC, 8.30-21.80% for IS, and 5.20-17.40% for SA. The LODs calculated for SDA are below the maximum limits allowed by the major pharmaceutical regulatory agencies, and presents superior precision and accuracy compared to the traditional calibration methods. Considering its simplicity and efficiency, SDA is an important new tool for accurate analyses of pharmaceuticals.

Determination of Trace Elements in Cow Placenta by Tungsten Coil Atomic Emission Spectrometry.

Tungsten coil atomic emission spectrometry (WCAES) is used to determine trace levels of Mn (403.1 nm) and Cr (425.5 nm) in cow placenta. All samples were collected in Ilha Solteira, SP, Brazil. The instrumental setup is based on a tungsten filament extracted from 150 W, 15 V microscope light bulbs, a solid state power supply, fused silica lens, crossed Czerny-Turner spectrograph, and a thermoelectrically cooled charge-coupled device detector. The limits of detection (LOD) and quantification (LOQ) for Cr are 2 and 8 µg L-1, and 20 and 60 µg L-1 for Mn, respectively. Recoveries for 0.30 mg L-1 spikes of each analyte were in the range 93.0-103.0%, and relative standard deviation (RSD) was between 6.50 and 7.20% for both elements. Placenta samples were microwave-assisted digested with diluted HNO3 and H2O2 and analyzed by WCAES. The results for Cr and Mn were compared with values obtained by tandem inductively coupled plasma mass spectrometry (ICP-MS/MS). No statistically significant difference was observed between the different methods by applying a paired t test at a 95% confidence level. The average concentrations of Cr and Mn in the placentas evaluated were 0.95 ± 0.22 and 2.64 ± 0.39 µg g-1, respectively. By using a short integration time, LODs for Cr and Mn were lower than values reported by recent works using a similar WCAES system.

Standard dilution analysis of beverages by microwave-induced plasma optical emission spectrometry.

In this work, standard dilution analysis (SDA) is combined with microwave-induced plasma optical emission spectrometry (MIP OES) to determine seven elements in coffee, green tea, energy drink, beer, whiskey and cachaça (Brazilian hard liquor). No sample preparation other than simple dilution in HNO3 1% v v(-1) is required. Due to relatively low plasma temperatures, matrix effects may compromise accuracies in MIP OES analyzes of complex samples. The method of standard additions (SA) offers enhanced accuracies, but is time-consuming and labor intensive. SDA offers a simpler, faster approach, with improved accuracies for complex matrices. In this work, SDA's efficiency is evaluated by spike experiments, and the results are compared to the traditional methods of external calibration (EC), internal standard (IS), and standard additions (SA). SDA is comparable to the traditional calibration methods, and it provides superior accuracies for applications involving ethanol-containing beverage samples. The SDA-MIP OES procedure is effective. Using only two calibration solutions, it may be easily automated for accurate and high sample throughput routine applications.

Evaluation of a mental health training intervention for multidisciplinary teams in primary care in Brazil: a pre- and posttest study.

OBJECTIVES: The aim of this research was to investigate whether a training intervention to enhance collaboration between mental health and primary care professionals improved the detection and management of mental health problems in primary health care in four large cities in Brazil. The training intervention was a multifaceted program over 96 h focused on development of a shared care model. METHOD: A quasiexperimental study design was undertaken with assessment of performance by nurse and general practitioners (GPs) pre- and postintervention. Rates of recognition of mental health disorders (compared with the General Health Questionnaire) were the primary outcome, while self-reports of patient-centered care, psychosocial interventions and referral were the secondary outcomes. RESULTS: Six to 8 months postintervention, no changes were observed in terms of rate of recognition across the entire sample. Nurses significantly increased their recognition rates (from 23% to 39%, P=.05), while GPs demonstrated a significant decrease (from 42% to 30%, P=.04). There were significant increases in reports of patient-centered care, but no changes in other secondary outcomes. CONCLUSIONS: Training professionals in a shared care model was not associated with consistent improvements in the recognition or management of mental health problems. Although instabilities in the local context may have contributed to the lack of effects, wider changes in the system of care may be required to augment training and encourage reliable changes in behavior, and more specific educating models are necessary.

Common mental disorders in Petrópolis-RJ: a challenge to integrate mental health into primary care strategies.

OBJECTIVE: Common mental disorders are present in more than 50% of patients attending primary care clinics. The main objectives of this study were to detect whether there is any special group of patients within the Family Health Strategy that should be considered to be in greater risk for common mental disorders and to recommend alternative interventions to aid these patients. METHOD: In 2002, a cross-sectional study on common mental disorders seen at Family Health Strategy centers was conducted in Petrópolis, State of Rio de Janeiro. RESULTS: Common mental disorders were associated with women (OR = 2.90; 95% CI 1.82-4.32), younger than 45 years of age (OR = 1.43; 95% CI 1.02-2.01), with a monthly per capita family income of less than US$40.00 (OR = 1.68; 95% CI 1.20-2.39), and without a partner (OR = 1.71; 95% CI 1.22-2.39). Illiteracy was associated with common mental disorders among patients who were not extremely poor. Social support networks such as going often to church (OR = 0.62; 95% CI 0.43-0.89); participating in artistic and sporting activities (OR = 0.42; 95% CI 0.26-0.70) and having at least four trusted relatives or friends (OR = 0.53; 95% CI 0.31-0.91) was inversely associated with common mental disorders. DISCUSSION: Poor women with little social support represent a special group at risk for common mental disorders in the primary care setting. Some countries have developed special interventions to treat patients with common mental disorders in primary care. CONCLUSION: Mental health care programs could include evidence-based psychosocial interventions to assist women in overcoming the vicious circle of poverty and dealing with their mental disorders.

Determinants of common mental disorders detection by general practitioners in primary health care in Brazil.

OBJECTIVE: Common mental disorders (CMD) are highly prevalent among patients attending primary care. Many of these disorders remain unrecognized by general practitioners (GPs), with the detection rates varying from 30 to 60%. This study aims to evaluate the CMD detection rates by Primary Heath Care (PHC) practitioners in Brazil-and factors that affect CMD detection. METHODS: A cross sectional study was conducted with users of five PHC units in the city of Petrópolis. The CMD prevalence of psychiatric morbidity was estimated by the General Health Questionnaire-12, and the physician's CMD detection was evaluated by a questionnaire completed by GPs after each consultation. RESULTS: Seven hundred and fourteen subjects participated of the study, and 400 (56%) were screened positive using GHQ-12 cut-off point of 2/3. GPs diagnosed 379 people with CMD (53.1%), and 256(36%) subjects were detected by both GHQ and the GPs with an OR of 3.04 (95% CI 2.23-4.13). CMD detection accuracy by GPs was 65%. There was a strong association between the detection of CMD and the report of medically unexplained physical symptoms by GPs. Being female, married, and a frequent service user was also related to higher detection rates. CONCLUSION: CMD detection rate was similar to those reported worldwide, but contrary to other studies, the presence of MUS increased detection rates. The high frequency of CMD in Primary Health Care highlights the need for improving GP and health worker's training in order to enable them to accurately recognize and treat psychological distress with evidence-based interventions.

Common mental disorders in Petrópolis-RJ: a challenge to integrate mental health into primary care strategies / Transtornos mentais comuns em Petrópolis-RJ: um desafio para a integração da saúde mental com a estratégia de saúde da família

OBJECTIVE: Common mental disorders are present in more than 50 percent of patients attending primary care clinics. The main objectives of this study were to detect whether there is any special group of patients within the Family Health Strategy that should be considered to be in greater risk for common mental disorders and to recommend alternative interventions to aid these patients. METHOD: In 2002, a cross-sectional study on common mental disorders seen at Family Health Strategy centers was conducted in Petrópolis, State of Rio de Janeiro. RESULTS: Common mental disorders were associated with women (OR = 2.90; 95 percent CI 1.82-4.32), younger than 45 years of age (OR = 1.43; 95 percent CI 1.02-2.01), with a monthly per capita family income of less than US$40.00 (OR = 1.68; 95 percent CI 1.20-2.39), and without a partner (OR = 1.71; 95 percent CI 1.22-2.39). Illiteracy was associated with common mental disorders among patients who were not extremely poor. Social support networks such as going often to church (OR = 0.62; 95 percent CI 0.43-0.89); participating in artistic and sporting activities (OR = 0.42; 95 percent CI 0.26-0.70) and having at least four trusted relatives or friends (OR = 0.53; 95 percent CI 0.31-0.91) was inversely associated with common mental disorders. DISCUSSION: Poor women with little social support represent a special group at risk for common mental disorders in the primary care setting. Some countries have developed special interventions to treat patients with common mental disorders in primary care. CONCLUSION: Mental health care programs could include evidence-based psychosocial interventions to assist women in overcoming the vicious circle of poverty and dealing with their mental disorders.

OBJETIVO: Transtornos mentais comuns estão presentes em cerca de 50 por cento dos pacientes atendidos nas unidades de atenção primária. Os principais objetivos deste estudo foram investigar a presença de grupos especiais de pacientes na Estratégia de Saúde da Família que devam ser considerados como em maior risco para transtornos mentais comuns e recomendar intervenções alternativas que auxiliem estes pacientes. MÉTODO: Em 2002, um estudo de corte transversal sobre transtornos mentais comuns foi realizado nas unidades do Programa de Saúde da Família em Petrópolis-RJ. RESULTADOS: A presença de transtornos mentais comuns estava associada a ser mulher (OR = 2,90; 95 por cento CI 1,82-4,32), ter menos de 45 anos (OR = 1,43; 95 por cento CI 1,02-2,01), com uma renda per capita familiar menor que U$40,00 (OR = 1,68; 95 por cento CI 1,20-2,39) e sem companheiro (OR = 1,71; 95 por cento CI 1,22-2,39). Analfabetismo se associava a transtornos mentais comuns em pacientes que não eram extremamente pobres. Redes de suporte social, tais como frequentar regularmente a igreja (OR = 0,62; 95 por cento CI 0,43-0,89), participar de atividades esportivas e artísticas (OR = 0,42; 95 por cento CI 0,26-0,70) e ter pelo menos quatro amigos ou parentes em quem se podia confiar (OR = 0,53; 95 por cento CI 0,31-0,91) estavam inversamente associadas a ter transtornos mentais comuns. DISCUSSÃO: Existe um grupo de risco especial para transtornos mentais comuns na atenção primária: mulheres, pobres, com pouco suporte social. Intervenções especiais para que sejam cuidadas na atenção primária têm sido desenvolvidas em outros países. CONCLUSÃO: Intervenções terapêuticas com comprovada evidência científica para apoiar essas mulheres a romper o círculo vicioso de pobreza e transtornos mentais podem ser inseridas nas ações de saúde mental.