A reliable method to prepare milligram size environmental samples to quantify metal(loid)s by high-resolution graphite furnace atomic absorption spectrometry.

We searched for an extraction method that would allow a precise quantification of metal(loid)s in milligram-size samples using high-resolution graphite furnace atomic absorption spectrometry (HR-GFAAS). We digested biological (DORM-4, DOLT-5 and TORT-3) and sediment (MESS-4) certified reference materials (CRMs) using nitric acid in a drying oven, aqua regia in a drying oven, or nitric acid in a microwave. In addition, we digested MESS-4 using a mixture of nitric and hydrofluoric acids in a drying oven. We also evaluated the effect of sample size (100 and 200 mg) on the extraction efficiency. Nitric acid extraction in a drying oven yielded the greatest recovery rates for all metal(loid)s in all tested CRMs (80.0 %-100.0 %) compared with the other extraction methods tested (67.3 %-99.2 %). In most cases, the sample size did not have a significant effect on the extraction efficiency. Therefore, we conclude that nitric acid digestion in a drying oven is a reliable extraction method for milligram-size samples to quantify metal(loid)s with HR-GFAAS. This validated method could provide substantial benefits to environmental quality monitoring programs by significantly reducing the time and costs required for sample collection, storage, transport and preparation, as well as the amount of hazardous chemicals used during sample extraction and analysis. •Sample digestion with nitric acid in a drying oven yielded the greatest recovery rates of metal(loid)s from biological and sediment certified reference materials.•The recovery rates of metal(loid)s from biological and sediment certified reference materials using nitric acid digestion in a drying oven ranged from 73 % to 100 %.•Digestion with nitric acid in a drying oven is a simple and reliable method to extract small size environmental samples for metal(loid)s quantification by high-resolution graphite furnace atomic absorption spectrometry.

Voltammetric Sensing of Nifedipine Using a Glassy Carbon Electrode Modified with Carbon Nanofibers and Gold Nanoparticles.

Nifedipine, a widely utilized medication, plays a crucial role in managing blood pressure in humans. Due to its global prevalence and extensive usage, close monitoring is necessary to address this widespread concern effectively. Therefore, the development of an electrochemical sensor based on a glassy carbon electrode modified with carbon nanofibers and gold nanoparticles in a Nafion® film was performed, resulting in an active electrode surface for oxidation of the nifedipine molecule. This was applied, together with a voltammetric methodology, for the analysis of nifedipine in biological and environmental samples, presenting a linear concentration range from 0.020 to 2.5 × 10-6 µmol L-1 with a limit of detection 2.8 nmol L-1. In addition, it presented a good recovery analysis in the complexity of the samples, a low deviation in the presence of interfering potentials, and good repeatability between measurements.

Distribution of Inorganic Contaminants Along the Coast of Ciudad de la Costa, Uruguay.

The aim of this work was to study the distribution of relevant inorganic contaminants in environmental samples from Ciudad de la Costa, the second most populated city of Uruguay. For this task aluminum (Al), cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb) levels were determined in sand, water, and plant material from six beaches that are located in the area. Analytical methods were successfully validated. Accuracy was ensured by using certified reference materials and spiking procedures. Average metal concentrations in sand and water samples were compared with the maximum limits established by international or national regulations (when available), being far below these limits in all cases. This may indicate that the inorganic contamination in the studied area is rather low, despite the rapid increase in anthropic activities in recent years. To give a deeper characterization of the ecosystem, metal accumulation and mobility within a common plant of the zone, Ammophila arenaria, were studied. Results showed that concentrations in roots were one order of magnitude higher in comparison to aerial parts. In addition, the bioaccumulation coefficient (BAC) showed that the plant accumulates Cd, Cr and Ni, while a low accumulation for Pb was observed. Finally, a Cr(VI) speciation analysis in Ammophila arenaria was performed, showing Cr(VI) percentages below 4.6%, which is relevant from the (eco)toxicological point of view due to the high environmental mobility and bioavailability of this valence state. This work constitutes the first environmental surveillance report of this kind, regarding this populated area of the country.

Unlocking the molecular realm: advanced approaches for identifying clinically and environmentally relevant bacteria

Rapid, effective, and specific identification of clinical and environmental bacterial pathogens is of major importance for their control. Traditionally, bacteria have been identified by phenotypic methods based on morphological, biochemical, and metabolic properties. While these methods are very useful in clinical practice, they have limitations including a poor ability to differentiate within and between species and time-consuming workflows. Newly developed molecular methods can greatly improve the accuracy of taxonomic characterization, identifying specific strains of medical or environmental importance. However, due to high costs and the need for trained professionals, these methods are not yet routine in diagnostic laboratories. Thus, disseminating knowledge on advances in molecular identification techniques is pivotal to make these methodologies accessible. The objective of this work was to review and discuss current molecular techniques for bacteria identification aiming to track and monitor microbial agents in clinical and environmental samples.

Hg Pollution Indices along the Reis Magos River Basin-Brazil: A Precursory Study.

Mercury is a metal present in the Earth's crust, but due to human contribution, its concentration can increase, causing environmental impacts to aquatic ecosystems, among others. The Reis Magos River Hydrographic Basin represents economic and socio-environmental importance for the state of Espírito Santo, Brazil. However, there are not many publications regarding the quality of water and sediments, so no data is reported concerning the total concentration of Hg. Thus, the present work aimed to evaluate the distribution of total Hg in water and sediments along this hydrographic basin. For a better inference, physicochemical parameters of the water were determined (temperature, pH, electrical conductivity, oxidation-reduction potential (ORP), turbidity, dissolved oxygen (DO), total dissolved solids (TDS), and salinity), and in the sediments, the contents of matter organic matter, pH, carbonates and granulometry. Mercury determination was performed by Thermodecomposition and Amalgamation Atomic Absorption Spectrometry (TDA AAS) with a DMA-80 spectrometer. The Hg determined in the water was lower than the limit of quantification, 0.14 µg∙L-1, which is lower than the maximum limits recommended by world reference environmental agencies. In the sediment samples, the Hg found were below 170 µg∙kg-1, values below which there is less possibility of an adverse effect on the biota. However, when the degree of anthropic contribution was evaluated using the Geoaccumulation index (IGeo), the contamination factor (CF), and the ecological risk potential index (EF), there was evidence of moderate pollution. Thus, this highlighted the need for monitoring the region since climatic variations and physical-chemical parameters influence the redistribution of Hg between the water/sediment interface.

Functionalized graphene quantum dots obtained from graphene foams used for highly selective detection of Hg2+ in real samples.

Here we report the use of graphene quantum dots (GQDs), obtained from 3D graphene foam, functionalized with 8-hydroxyquinoline (8-HQ) for the sensitive and selective detection of Hg2+ via front-face fluorescence. The great surface area and active groups within the GQDs permitted the functionalization with 8-HQ to increase their selectivity toward the analyte of interest. The fluorescence probe follows the Stern-Volmer model, yielding a direct relationship between the degree of quenching and the concentration of the analyte. Diverse parameters, including the pH and the use of masking agents, were optimized in order to improve the selectivity toward Hg2+ down to a limit of detection of 2.4 nmol L-1. It is hereby demonstrated that the functionalized GQDs work perfectly fine under adverse conditions such as acidic pH and in the presence of a large number of cationic and anionic interferences for the detection of Hg2+ in real samples. Parallel measurements using cold vapor atomic fluorescence spectrometry also demonstrated an excellent correlation with the front-face fluorescence method applied here for real samples including tap, river, underground, and dam waters.

An electrochemical sensor-based carbon black associated with a modified mixed oxide (SiO2/TiO2/Sb2O5) for direct determination of thiamethoxam in raw honey and water samples.

The study aimed to develop an electrochemical sensor based on glassy carbon, mixed oxide (SiO2/TiO2/Sb2O5), and carbon black. The material was synthesized, characterized, and used to determine thiamethoxam in raw honey and water. The morphologic structure and electrochemical performance of the sensor was characterized by scanning electron microscopy and cyclic voltammetry. Differential pulse voltammetry with a concentration of 0.1 mol L-1 of Britton-Robinson buffer at pH 7.0 allowed the generation of a method to determine thiamethoxam in a linear range of 0.25 to 100.5 µmol L-1 and with a limit of detection of 0.012 µmol L-1. The system efficiently quantified traces of thiamethoxam in raw honey and tap water samples. The modified sensor did not present interferences of K+, Na+, Ca2+, Mg2+, glyphosate, imidacloprid, and carbendazim. In addition, the device showed good recovery values for thiamethoxam when applied directly to honey and water samples without any treatment, presenting an electrochemical sensor to monitor real-time hazardous substances in environmental and food matrices.

Chromogenic Escherichia coli reporter strain for screening DNA damaging agents.

The presence of pollutants in soil and water has given rise to diverse analytical and biological approaches to detect and measure contaminants in the environment. Using bacterial cells as reporter strains represents an advantage for detecting pollutants present in soil or water samples. Here, an Escherichia coli reporter strain expressing a chromoprotein capable of interacting with soil or water samples and responding to DNA damaging compounds is validated. The reporter strain generates a qualitative signal and is based on the expression of the coral chromoprotein AmilCP under the control of the recA promoter. This strain can be used simply by applying soil or water samples directly and rendering activation upon DNA damage. This reporter strain responds to agents that damage DNA (with an apparent detection limit of 1 µg of mitomycin C) without observable response to membrane integrity damage, protein folding or oxidative stress generating agents, in the latter case, DNA damage was observed. The developed reporter strain reported here is effective for the detection of DNA damaging agents present in soils samples. In a proof-of-concept analysis using soil containing chromium, showing activation at 15.56 mg/L of Cr(VI) present in soil and leached samples and is consistent with Cr(III) toxicity at high concentrations (130 µg). Our findings suggest that chromogenic reporter strains can be applied for simple screening, thus reducing the number of samples requiring analytical techniques.

SARS-CoV-2 in Human Sewage and River Water from a Remote and Vulnerable Area as a Surveillance Tool in Brazil.

In the present study, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was monitored in environmental samples from rural and vulnerable areas (a presidio, worker accommodation units, and river waters upstream and downstream of a rural community) from Minas Gerais State region, Southern Brazil, in August 2020. The sampling was performed prior to official declaration of the coronavirus disease (COVID-19) cases in those sites. SARS-CoV-2 RNA was detected in the presidio and workers accommodation units (3.0 × 104 virus genome copies (GC)/mL and 4.3 × 104 GC/mL of sewage, respectively). While SARS-CoV-2 was not detected in the river water upstream of the rural community, SARS-CoV-2 RNA was detected in downstream river waters (1.1 × 102 SARS-CoV-2 GC/mL). The results obtained in this study highlight the utility of SARS-CoV-2 monitoring in wastewater and human sewage as a non-invasive early warning tool to support health surveillance in vulnerable and remote areas, particularly in development countries.

Vortex-assisted magnetic solid-phase extraction of cadmium in food, medicinal herb, and water samples using silica-coated thiol-functionalized magnetic multiwalled carbon nanotubes as adsorbent.

The current work focuses on the facile and effective synthesis of a new nanocomposite based on multiwalled carbon nanotubes (MWCNT) decorated with magnetic core-shell Fe3O4@SiO2 and functionalized with 3-mercaptopropyltrimethoxysilane (3-MPTS) used in the vortex-assisted dispersive magnetic solid-phase extraction (VA-DMSPE) of Cd(II) ions in environmental and food samples. The nanocomposite was characterized and the parameters that influenced the VA-DMSPE were optimized through a fractional factorial design 25-1. The proposed method provided a preconcentration factor of 33.14 times, detection and quantification limits of 0.090 µg L-1 and 0.302 µg L-1, respectively, and a linearity range of 0.001-40.0 µg L-1. The developed method was effectively applied to preconcentrate and determine Cd(II) in water, tobacco, green tea leaves, ginkgo biloba, carrots, and rice samples, and its accuracy was evaluated using GF AAS.

Occurrence of extended-spectrum beta-lactamase (ESBL) and carbapenemases among ampicillin-resistant enterobacteriales recovered from a municipal raw sewage in Minas Gerais, Brazil

SUMMARY Introduction: The capacity of resistance to ß-lactam among enterobacteriales is notable, mainly into water environment. Herein, many species of this family have the ability to carrier and produce ß-lactamases enzymes, such as extended-spectrum ß-lactamases (ESBLs) and carbapenemases. However, contrary to clinical settings, where the distribution of resistant bacteria is well documented, the evidence of resistant pathogens in the domestic sewage has been little explored, especially in Brazil. Thus, we aimed to investigate the occurrence of ESBL and carbapenemases between ampicillin-resistant enterobacteriales recovered from a municipal raw sewage in Minas Gerais, Brazil. Methods: Enterobacteriales were isolated from sewage samples on MacConkey agar supplemented with ampicillin. Species identification was performed by biochemical and morphological methods and the resistance profile determined by the Kirby-Bauer test. The production of ESBL and carbapenemase was investigated in all isolates by phenotypic tests. Results and discussion: A total of 45 species of enterobacteriales resistant to ampicillin were recovered (37 Escherichia coli, four Klebsiella pneumoniae, and one Klebsiella oxytoca, Citrobacter freundii and Pantoea agglomerans). Most isolates showed a high ß-lactam susceptibility profile (14/45, 31.1 %), however E. coli with decreased susceptibility to imipenem was detected (2/37; 2.7 %). ESBL-positive isolates were mostly identified as E. coli (10/45; 22.2 %), but no isolates were positive carbapenemase. Conclusion: Domestic sewage is an important source of ß-lactams resistant determinants in Brazil.

Introdução: a capacidade de resistência aos beta-lactâmicos entre enterobacteriales é notável, principalmente no ambiente aquático. Nessa direção, muitas espécies desta família têm a capacidade de transportar e produzir enzimas ß-lactamases, especialmente a ß-lactamases de espectro estendido (ESBL) e as carbapenemases. Porém, ao contrário do cenário clínico, onde a distribuição de bactérias resistentes é bem documentada, as evidências de patógenos resistentes no esgoto doméstico têm sido pouco exploradas, principalmente no Brasil. Assim, objetivamos investigar a ocorrência de ESBL e carbapenemases entre enterobacteriales resistentes à ampicilina recuperadas de um esgoto bruto municipal em Minas Gerais, Brasil. Métodos: enterobacteriales foram isoladas de amostras de esgoto em ágar MacConkey suplementado com ampicilina. A identificação das espécies foi realizada por métodos bioquímicos e morfológicos e o perfil de resistência determinado pelo teste de Kirby-Bauer. A produção de ESBL e carbapenemase foi investigada em todos os isolados por testes fenotípicos. Resultados e discussão: foram recuperadas 45 isolados de enterobacteriales resistentes à ampicilina (37 Escherichia coli, quatro Klebsiella pneumoniae e uma Klebsiella oxytoca, Citrobacter freundii e Pantoea agglomerans). A maioria dos isolados apresentou um perfil de alta susceptibilidade aos ß-lactâmicos (14/45, 31,1 %), porém E. coli com susceptibilidade diminuída ao imipenem foi detectada (2/37; 2,7 %). Os isolados ESBL-positivos foram identificados principalmente como E. coli (10/45; 22,2 %), mas nenhum isolado foi positivo para a carbapenemase. Conclusão: o esgoto doméstico é uma importante fonte de determinantes de resistência aos ß-lactâmicos no Brasil.

Introducción: la capacidad de resistencia a betalactámicos entre enterobacteriales es notable, principalmente en el medio acuático. En este sentido, muchas especies de esta familia tienen la capacidad de transportar y producir enzimas ß-lactamasas, especialmente ß-lactamasas de espectro extendido (BLEE) y carbapenemasas. Sin embargo, en contraste con el escenario clínico, donde la distribución de bacterias resistentes está bien documentada, la evidencia de patógenos resistentes en las aguas residuales domésticas ha sido poco explorada, especialmente en Brasil. Por lo tanto, nuestro objetivo es investigar la ocurrencia de BLEE y carbapenemasas entre enterobacteriales resistentes a ampicilina recuperadas de un alcantarillado municipal sin tratar en Minas Gerais, Brasil. Métodos: se aislaron enterobacteriales de muestras de aguas residuales en agar MacConkey suplementado con ampicilina. La identificación de las especies se realizó mediante métodos bioquímicos y morfológicos y el perfil de resistencia se determinó mediante la prueba de Kirby-Bauer. La producción de BLEE y carbapenemasa se investigó en todos los aislamientos mediante pruebas fenotípicas. Resultados y discusión: se recuperaron 45 aislamientos de enterobacteriales resistentes a ampicilina (37 Escherichia coli, cuatro Klebsiella pneumoniae y una Klebsiella oxytoca, Citrobacter freundii y Pantoea agglomerans). La mayoría de los aislamientos tenían un perfil de susceptibilidad alto a los (3-lactámicos (14/45, 31,1 %), pero se detectó E. coli con susceptibilidad reducida al imipenem (2/37; 2,7 %). Los aislamientos positivos para BLEE se identificaron principalmente como E. coli (10/45; 22,2 %), pero ningún aislado fue positivo para carbapenemasa. Conclusión: las aguas residuales domésticas son una fuente importante de determinantes de la resistencia a los ß-lactámicos en Brasil.

Elemental Speciation Analysis in Environmental Studies: Latest Trends and Ecological Impact.

Speciation analysis is a key aspect of modern analytical chemistry, as the toxicity, environmental mobility, and bioavailability of elemental analytes are known to depend strongly on an element's chemical species. Henceforth, great efforts have been made in recent years to develop methods that allow not only the determination of elements as a whole, but also each of its separate species. Environmental analytical chemistry has not ignored this trend, and this review aims to summarize the latest methods and techniques developed with this purpose. From the perspective of each relevant element and highlighting the importance of their speciation analysis, different sample treatment methods are introduced and described, with the spotlight on the use of modern nanomaterials and novel solvents in solid phase and liquid-liquid microextractions. In addition, an in-depth discussion of instrumental techniques aimed both at the separation and quantification of metal and metalloid species is presented, ranging from chromatographic separations to electro-chemical speciation analysis. Special emphasis is made throughout this work on the greenness of these developments, considering their alignment with the precepts of the Green Chemistry concept and critically reviewing their environmental impact.

Detección de Leptospira spp. (Spirochaetales: Leptospiraceae) en muestras ambientales de regiones habitadas por poblaciones vulnerables del norte argentino / Leptospira spp. (Spirochaetales: Leptospiraceae) detection in environmental samples from geographical regions inhabited by vulnerable communities in northern Argentina

Resumen La leptospirosis continúa siendo hoy en día un problema para la salud pública, principalmente en poblaciones de bajos recursos socioeconómicos. En este trabajo se presenta la detección de leptospiras patógenas en muestras ambientales (aguas y barros) provenientes de regiones del norte argentino (provincias de Formosa, Salta, Santiago del Estero, Misiones y Chaco) con variadas características climatológicas habitadas por poblaciones vulnerables. De las 89 muestras analizadas, en el 24,7% fue posible detectar molecularmente la presencia de leptospiras patógenas. La prevalencia por tipo de muestra fue de 27,8% para las aguas y 11,8% para los barros. Todas las localidades muestreadas presentaron al menos una muestra positiva a alguna de las pruebas realizadas, por lo que el presente trabajo refleja la necesidad de profundizar los estudios de la leptospirosis en distintas regiones de la Argentina.

Abstract Leptospirosis remains as a major public health problem nowadays, mainly affecting vulnerable communities with low socioeconomic resources. In this study, the molecular detection of pathogenic leptospires from environmental samples (water and mud) from northern Argentina (Formosa, Salta, Santiago del Estero, Misiones and Chaco provinces) is described. Samples were obtained from regions with varied climatological features, all inhabited by vulnerable communities. From the 89 samples that were analyzed, 24.7% showed molecular evidence of the presence of pathogenic leptospires. Prevalence by sample type was: 27.8% in water samples and 11.8% in mud samples. All the sampled regions showed at least one positive sample. This result highlights the need of further research regarding leptospirosis in different regions of Argentina.

N-compounds speciation analysis in environmental samples using ultrasound-assisted solid-liquid extraction and non-chromatographic techniques.

A fast, efficient, and non-chromatographic method was presented in this study for nitrite, nitrate, and p-nitrophenol (N-compounds) extraction and speciation analysis of environmental samples. By applying ultrasound-assisted solid-liquid extraction (USLE), analytes were efficiently extracted from water, soil, or sediment collected in areas of environmental disaster. These analytes were selectively converted to NO(g) through UV photolysis (NO3-), H2O2/UV photocatalysis (PNP), and direct conversion (NO2-). Following conversion, NO(g) was separated from the liquid phase and determined by high-resolution continuum source molecular absorption spectrometry (HR-CS MAS). The LODs obtained were 0.097 ± 0.004 mg L-1 for nitrite, 0.119 ± 0.004 mg L-1 for nitrate, and 0.090 ± 0.006 mg L-1 for p-nitrophenol. On applying this speciation method to environmental samples, concentrations were found to be up to 0.99 ± 0.03 mg L-1 (NO2-), 49.80 ± 2.5 mg L-1 (NO3-), and 0.10 ± 0.02 mg L-1 (PNP). Finally, addition/recovery study of real water, soil, and sediment samples showed 101 ± 2% recovery for NO2-, 100 ± 1% for NO3-, and 96 ± 5% for PNP.

Metabarcoding advances for ecology and biogeography of Neotropical protists: what do we know, where do we go? / Ecologia e biogeografia de protistas Neotropicais usando metabarcoding: O que sabemos? Para onde iremos?

Abstract: The Neotropics is one of the most diverse regions of the globe in terms of plants and animal species. Regarding the microbial world, however, little is known about the diversity and biogeography patterns of microorganisms in the Neotropics. The biogeography of several microbial taxonomic groups is still missing and/or incomplete, such as the protists. Despite the hard taxonomic identification of protists, the advance of molecular techniques (e.g., metabarcoding) have allowed to better explore the distribution of several protistan groups. Our goal here was to summarize the available information of Neotropical protists, focusing on metabarcoding studies, to explore what these data evidence on their ecology and biogeography. For this, we reviewed the findings from all articles that focused on or included the terrestrial protists using a metabarcoding approach and identified the gaps and future perspectives in this research field. We found that Neotropical protistan diversity patterns seem to be, at least in part, congruent with that of macro-organisms and, different than plants and bacteria, just weakly explained by environmental variables. We argue that studies with standardized protocols including different ecoregions are necessary, such as temperate forests, grasslands, and savannas from Southern of South America and Northern Atlantic Forest, to fully characterize the ecology and biogeography on Neotropical protists. Furthermore, dismembering evolutionary lineages and functional guilds of protists are important to better understand the relationship between diversity, dispersal abilities, and functionality of particular taxa of protists in their habitats.

Resumo: A região Neotropical é uma das mais diversas regiões do globo em termos de espécies vegetais e animais. Em relação ao mundo microbiano, entretanto, pouco se sabe sobre a diversidade e os padrões biogeográficos dos microrganismos no Neotrópico. Nesse contexto, a biogeografia de diversos grupos taxonômicos microbianos ainda é escasso e/ou incompleto como os protistas, devido à difícil identificação taxonômica de tais microscópicos organismos. Neste contexto, o avanço dos dados moleculares de amostras ambientais (por exemplo, metabarcoding) permitiu explorar a distribuição de vários grupos de protistas. Nosso objetivo aqui foi resumir as informações disponíveis dos protistas neotropicais, com foco em metabarcoding, para explorar o que esses dados evidenciam sobre sua ecologia e biogeografia. Para isso, revisamos os resultados de todos os artigos que enfocavam ou incluíam os protistas terrestres usando uma abordagem de metabarcoding e identificamos as lacunas e as perspectivas futuras neste campo de pesquisa. Os padrões de diversidade dos protistas Neotropicais parecem ser, pelo menos em parte, congruentes com os de macroorganismos e, diferentes das plantas e bactérias, sendo pouco explicados por variáveis ambientais. Estudos com protocolos padronizados incluindo diferentes Ecorregiões são necessários, como em florestas temperadas, campos nativos e savanas no sul da América do Sul e no norte da Mata Atlântica, para melhor caracterizar a ecologia e biogeografia de protistas Neotropicais. Além disso, é importante diferenciar linhagens evolutivas e guildas funcionais de protistas para entender melhor a relação entre diversidade, capacidade de dispersão e funcionalidade de determinados táxons de protistas em seus habitats.

Pesticides determination in foods and natural waters using solid amalgam-based electrodes: Challenges and trends.

The intensive use of pesticides in agricultural practices has promoted the appearance of environmental and public health problems. So, there has been a sharp increase in the development of simple, fast, sensitive, selective, and low-cost methods to analyse pesticides. Among them, electroanalytical methods have been frequently employed; however, the performance of these methods is strongly influenced by the working electrode material and so an adequate choice is critical to success of the analysis. Solid amalgam-based electrodes have been widely used; this review critically discusses the evolution of the preparation and use of these electrodes and their application in analysis of pesticides from different chemical classes, indicating challenges and trends in pesticide electroanalysis. The relationship between pesticides' chemical structures and electrochemical behaviour on a mercury-based electrode is explored in order to indicate the use of electroanalysis in pesticide determination.

Trace analysis of parabens preservatives in drinking water treatment sludge, treated, and mineral water samples.

Parabens have been widely used as antimicrobial agents, mainly in food products, pharmaceuticals, and cosmetics. Although they are known as safe preservatives, they also cause some harm to human health, which has been discussed lately. Therefore, the aim of this study was to evaluate the occurrence of nine parabens (including isomers) in mineral and drinking waters, besides in drinking water treatment sludge (DWTS) samples with determination by liquid chromatography tandem mass spectrometry (LC-MS/MS). Both methods solid phase extraction (SPE) and QuEChERS were validated. Calibration curves showed a correlation coefficient of 0.99 for all compounds. LOQ values ranged from 0.04 to 4 µg L-1 in aqueous matrices and from 5 to 500 ng g-1 in DWTS. Recoveries between 70 and 115% were reached with RSD below 20% for all compounds in SPE whereas recoveries between 62 and 119% were found with RSD below 20% for almost all compounds in QuEChERS. Matrix effect had low values (< 20%); it was only above 20% for methylparaben in the SPE and for pentylparaben in the QuEChERS. Using a quick and simple extraction procedures with SPE, QuEChERS, and LC-MS/MS analyses, these methods proved to be selective and sensitive. They were successfully applied to real samples (treated water, mineral water, and sludge), and methylparaben was detected at concentration levels below 0.242 µg L-1 in mineral and treated water samples and 10 ng g-1 in DWTS samples.

Speciation of As in environmental samples using the nano-TiO2/PCHG-FAAS online system.

This work presents an alternative method for arsenic speciation using the nano-TiO2 hydride generation photocatalytic hydride generation (PCHG) system, which is easily separated from the medium. Nano-TiO2 was studied as photocatalyst to reduction of arsenic species by UV-induced with formic acid and atomic absorption detection of different forms of arsenic [As (III), As (V), dimethylarsinic acid (DMA)] in environmental samples (water, sediment and plant). The effect of the average pH, the organic acid concentration, the ultraviolet irradiation time and their amount were investigated. With the presence of formic acid, the process was more effective in the reduction of arsenic when compared to other organic acids, mainly acetic acid. In addition, the photocatalytic hydride generation and flame atomic absorption spectrometry (nano-TiO2/PCHG-FAAS) increased the identification and quantification of different arsenic species. The ultrasound extraction procedure was used as a method to prepare samples with solutions of 1.0 mol L-1 phosphoric acid. The accuracy of the measurements (n = 12), calculated as relative standard deviation, was less than 8.6%. The detection limits for As (III) and As (total) in samples were 0.418 and 0.574 µg g-1, respectively.

Genetic Background of ß-Lactamases in Enterobacteriaceae Isolates from Environmental Samples.

The prevalence of ß-lactamase-producing Enterobacteriaceae has increased worldwide. Although antibiotic-resistant bacteria are usually associated with hospitals, there are a growing number of reports of resistant bacteria in other environments. Concern about resistant microorganisms outside the hospital setting highlights the need to investigate mechanisms of antibiotic resistance in isolates collected from the environment. The present study evaluated the resistance mechanism to ß-lactam antibiotics in 40 isolates from hospital sewage and surface water from the Dilúvio Stream, Porto Alegre City, Southern Brazil. The multiplex PCR technique was used to detect several resistance genes of ß-lactamases: extended-spectrum ß-lactamases (ESBLs), carbapenemases, and ß-lactamase AmpC. After genes, detection amplicons were sequenced to confirm their identification. The clonal relationship was established by DNA macrorestriction using the XbaI enzyme, followed by pulsed-field gel electrophoresis (PFGE). The results indicated that resistance genes were present in 85% of the isolates. The most prevalent genes encoded narrow-spectrum ß-lactamase, such as TEM-1 and SHV-1 with 70% of the strains, followed by carbapenemase KPC and GES (45%), ESBL types SHV-5 and CTX-M-8 (27.5%), and AmpC (ACT-1/MIR-1) (2.5%). Twelve isolates contained only one resistance gene, 14 contained two, and eight isolates had three resistance genes. PFGE indicated a clonal relationship among K. pneumoniae isolates. It was not possible to establish a clonal relationship between Enterobacter sp. isolates. The results highlight the potential of these resistance genes to spread in the polluted environment and to present a health risk to communities. This report is the first description of these resistance genes present in environmental samples other than a hospital in the city of Porto Alegre/RS.

Multivariate calibration-assisted high-performance liquid chromatography with dual UV and fluorimetric detection for the analysis of natural and synthetic sex hormones in environmental waters and sediments.

A green method is reported based on non-sophisticated instrumental for the quantification of seven natural and synthetic estrogens, three progestagens and one androgen in the presence of real interferences. The method takes advantage of: (1) chromatography, allowing total or partial resolution of a large number of compounds, (2) dual detection, permitting selection of the most appropriate signal for each analyte and, (3) second-order calibration, enabling mathematical resolution of incompletely resolved chromatographic bands and analyte determination in the presence of interferents. Consumption of organic solvents for cleaning, extraction and separation are markedly decreased because of the coupling with MCR-ALS (multivariate curve resolution/alternating least-squares) which allows the successful resolution in the presence of other co-eluting matrix constituents. Rigorous IUPAC detection limits were obtained: 6-24 ng L(-1) in water, and 0.1-0.9 ng g(-1) in sediments. Relative prediction errors were 2-10% (water) and 1-8% (sediments).