Identification and occurrence of microcystins in freshwaters and fish from a eutrophic dam through LC-HRMS.

Microcystins (MCs) are cyclic heptapeptides originating from various cyanobacteria in eutrophic aquatic environments. Their potential consequences on ecosystems and public health underscores the need to explore MCs' occurrence. In this study, liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) analysis and a suspect screening workflow supported by open-source tools were employed for the determination of MCs in freshwater and biota samples from a eutrophic dam in Uruguay.

Paleoenvironmental characterization and historical trends of polycyclic aromatic hydrocarbons (PAHs) of Nutrias Lagoon, Uruguay.

Concentrations of polycyclic aromatic hydrocarbons were assessed in a sediment core retrieved from Nutrias Lagoon, located within the Rocha Lagoon Protected Area along the SE Uruguayan coast. Using aPb chronology, we reconstructed the historical accumulation of polycyclic aromatic hydrocarbons over the past 123 years (1895-2018). This study, the first of its kind in Uruguay, fills a research gap in understanding historical PAH accumulation and source changes.

Comparative deterministic and probabilistic approaches for assessing the aquatic ecological risk of pesticides in a mixed land use basin: A case study in Uruguay.

Environmental concentrations of 25 pesticides in superficial water were employed to conduct an ecological risk assessment (ERA) in a mixed land-use basin utilized as a drinking water source. A deterministic risk assessment (RQ) was utilized to evaluate the chronic risk to aquatic biota, while a probabilistic risk assessment (PRA) approach was applied to assess the acute and chronic risk in the most sensitive species and at the community level. A high risk was identified for insecticides (pyrethroids, organophosphates and organochlorines).

Determination of Microcystins in Fish Tissue by ELISA and MALDI-TOF MS Using a Highly Specific Single Domain Antibody.

The development of simple, reliable, and cost-effective methods is critically important to study the spatial and temporal variation of microcystins (MCs) in the food chain. Nanobodies (Nbs), antigen binding fragments from camelid antibodies, present valuable features for analytical applications. Their small antigen binding site offers a focused recognition of small analytes, reducing spurious cross-reactivity and matrix effects.

Multicompartmental monitoring of legacy and currently used pesticides in a subtropical lake used as a drinking water source (Laguna del Cisne, Uruguay).

A pilot annual monitoring survey (April 2018-March 2019) was conducted to investigate the presence of pesticides in superficial water and fish in Laguna del Cisne, one of the most critical drinking water sources in Uruguay. A total of 25 pesticide residues were detected in superficial water (89.3 % of the samples).

Determination of glyphosate and AMPA in freshwater and soil from agroecosystems by 9-fluorenylmethoxycarbonyl chloride derivatization and liquid chromatography - fluorescence detection and tandem mass spectrometry.

The herbicide glyphosate (GLY) and its metabolite aminophosphonic acid (AMPA) are troublesome compounds for analysis in the environment. Here we report a reliable technique for GLY and AMPA determination in freshwater and soils by means of derivatization with 9-fluorenylmethoxycarbonyl chloride (FMOC-Cl) and further liquid chromatography with fluorescence detection (FLD) and tandem mass spectrometry (MS/MS) analysis. Selected experiments were carried out to evaluate selectivity, sensitivity, repeatability, linearity and quantification performance in both matrices.

Salt marshes as the final watershed fate for meso- and microplastic contamination: A case study from Southern Brazil.

Plastics pose a major threat to aquatic ecosystems especially in smaller size fractions. Salt marshes play a crucial role in maintaining the coastal zone and aquatic food web, yet their contamination, including by plastic materials, is still poorly investigated. This work investigated meso- (MEP, 5-25 mm) and microplastic (MIP, 1 μm-5 mm) contamination of a salt marsh, which reached average levels of 279.

Modeling microplastic with polyethylene (PE) spherical particles: a differential scanning calorimetry approach for quantification.

Detection, identification, and quantification of microplastics have become increasingly relevant for determining their contribution and role in environmental pollution. Thermal analysis is positioned as one of the alternative techniques employed to quantify microplastics. However, a deeper investigation that explores its capabilities is required, since in techniques such as difference scanning calorimetry (DSC), the result of the melting curve is potentially affected by the size of the micro particles.

Sulfur precursor and citric acid effect on SnS nanoparticles and their influence on the photodegradation activity of selected organic compounds.

Semiconductor nanoparticle-mediated photocatalysis is an attractive option for water decontamination, being the semiconductors as SnS with a bandgap in the visible region, the most promising materials. In the present work, we evaluated the influence of important parameters in the photocatalytic application of SnS nanoparticles. Our results show that the presence of citric acid (used as a capping agent) restricts the formation of hexagonal nanoparticles.

Identification of microplastics in wastewater samples by means of polarized light optical microscopy.

Many reports state the potential hazards of microplastics (MPs) and their implications to wildlife and human health. The presence of MP in the aquatic environment is related to several origins but particularly associated to their occurrence in wastewater effluents. The determination of MP in these complex samples is a challenge.

Basin-scale monitoring and risk assessment of emerging contaminants in South American Atlantic coastal lagoons.

Emerging contaminants (ECs) such as pharmaceuticals, personal care products, drugs of abuse and polar pesticides are under particular attention due to their high consumption, frequent detection in the environment and reported ecotoxicological risk. This study investigates the occurrence and distribution of multiclass of ECs in surface waters at basin scale of two Atlantic coastal lagoons of Uruguay, South America. For this purpose, a target screening approach covering up to 362 compounds was employed using nanoflow liquid chromatography - high resolution mass spectrometry (nanoLC/HRMS).

Determination of multiclass, semi-polar pesticide residues in fatty fish muscle tissue by gas and liquid chromatography mass spectrometry.

With the aim of monitoring multiclass semi-polar pesticide residues in freshwater fatty fish, two QuEChERS approaches (so-called acetate buffered and unbuffered versions) were evaluated for the determination of 77 pesticide residues. Compounds were selected according to the dominant rainfed agriculture activities in South America. Unbuffered QuEChERS was finally chosen for validation purposes owing that it provided the best results in terms of recovery yields.

Identification and quantitation of semi-crystalline microplastics using image analysis and differential scanning calorimetry.

There are several techniques used to analyze microplastics. These are often based on a combination of visual and spectroscopic techniques. Here we introduce an alternative workflow for identification and mass quantitation through a combination of optical microscopy with image analysis (IA) and differential scanning calorimetry (DSC).

Occurrence of pesticide residues in fish from south American rainfed agroecosystems.

Environmental sustainability of South American rainfed agroecosystems is of current concern. In this work, we evaluate the occurrence of multiple pesticide residues in muscle tissue of wild fish species from two large rivers in South America (Uruguay and Negro Rivers). Two sampling campaigns (representing summer and winter crops) were performed during 2015 targeting a wide biodiversity of fish species used for human consumption (ranging from migratory to non-migratory and from detritivorous to top-predators).

Degradation of imazalil, orthophenylphenol and pyrimethanil in Clementine mandarins under conventional postharvest industrial conditions at 4°C.

The degradation of the postharvest fungicides imazalil, orthophenylphenol, and pyrimethanil was studied on Clementine mandarins during packinghouse storage for a 28day period at 4°C. Fruits to which orthophenylphenol was applied, were treated with imazalil and pyrimethanil at doses of 1000 and 2000mgL(-1), using cascade application for the later and cascade and wax for the former. The decay of the three fungicides was evaluated using an in-house validated analytical procedure that includes the extraction and dispersive clean up of the samples followed by the GC-MS determination of the pesticide residues.

Inclusion of 1-naphthylacetic acid and 2-(1-naphthyl)acetamide into three typical multiresidue methods for LC/MS/MS analysis of tomatoes and zucchini.

In spite of high plant growth regulator application rates, little has been reported in the literature on determination of their residues in fruits and vegetables. This would be useful in monitoring good manufacturing practices and overall safety through the enforcement of maximum residue levels (MRLs). The present work describes method validation for the determination of 1-naphthylacetic acid (NAA) and 2(1-naphthyl)acetamide (NAAm) in tomato and zucchini using the mini-Luke, ethyl acetate (EtOAc) and acetate-buffered quick, easy, cheap, effective, rugged, and safe (QuEChERS) methods.

Occurrence and distribution study of residues from pesticides applied under controlled conditions in the field during rice processing.

The results of an experiment to study the occurrence and distribution of pesticide residues during rice cropping and processing are reported. Four herbicides, nine fungicides, and two insecticides (azoxystrobin, byspiribac-sodium, carbendazim, clomazone, difenoconazole, epoxiconazole, isoprothiolane, kresoxim-methyl, propanil, quinclorac, tebuconazole, thiamethoxam, tricyclazole, trifloxystrobin, λ-cyhalotrin) were applied to an isolated rice-crop plot under controlled conditions, during the 2009-2010 cropping season in Uruguay. Paddy rice was harvested and industrially processed to brown rice, white rice, and rice bran, which were analyzed for pesticide residues using the original QuEChERS methodology and its citrate variation by LC-MS/MS and GC-MS.

Photolytic and photocatalytic degradation of quinclorac in ultrapure and paddy field water: identification of transformation products and pathways.

Quinclorac (QNC) is an effective but rather persistent herbicide commonly used in rice production. This herbicide presents a mean persistence in the environment so its residues are considered of environmental relevance. However, few studies have been conducted to investigate its environmental behavior and degradation.

Detection of pesticides in active and depopulated beehives in Uruguay.

The influence of insecticides commonly used for agricultural purposes on beehive depopulation in Uruguay was investigated. Honeycombs, bees, honey and propolis from depopulated hives were analyzed for pesticide residues, whereas from active beehives only honey and propolis were evaluated. A total of 37 samples were analyzed, representing 14,800 beehives.

Use of an accurate-mass database for the systematic identification of transformation products of organic contaminants in wastewater effluents.

In this article, a systematic approach is proposed to assist and simplify the identification of transformation products (TPs) of organic contaminants. This approach is based on the use of characteristic fragmentation undergone by organic contaminants during MS/MS fragmentation events, and the relationship and consistency with the transformations experimented by these chemicals in the environment or during water treatment processes. With this in mind, a database containing accurate-mass information of 147 compounds and their main fragments generated by CID MS/MS fragmentation experiments was created using an LC-QTOF-MS/MS system.

Analytical improvements of hybrid LC-MS/MS techniques for the efficient evaluation of emerging contaminants in river waters: a case study of the Henares River (Madrid, Spain).

Purpose: Instrumental capabilities and software tools of modern hybrid mass spectrometry (MS) instruments such as high-resolution mass spectrometry (HRMS), quadrupole time-of-flight (QTOF), and quadrupole linear ion trap (QLIT) were experimentally investigated for the study of emerging contaminants in Henares River water samples.

Methods: Automated screening and confirmatory capabilities of QTOF working in full-scan MS and tandem MS (MS/MS) were explored when dealing with real samples. Investigations on the effect of sensitivity and resolution power influence on mass accuracy were studied for the correct assignment of the amoxicillin transformation product 5(R) amoxicillin-diketopiperazine-2',5' as an example of a nontarget compound.

Determination of coumaphos, chlorpyrifos and ethion residues in propolis tinctures by matrix solid-phase dispersion and gas chromatography coupled to flame photometric and mass spectrometric detection.

A new analytical method has been developed and successfully evaluated in routine application for the quantitative analysis of a selected group of organophosphate pesticides (coumaphos, chlorpyrifos and ethion) which can be found at trace levels in propolis tinctures (ethanolic propolis extracts); a valuable commodity used as raw material in the food and pharmaceutical industries for which there have been few attempts for pesticide residue analysis reported in the literature. The proposed methodology is based on matrix solid phase dispersion (MSPD) using aluminum sulfate anh. a novel dispersant material and subsequent column chromatography clean-up in silica gel prior to gas chromatography (GC) with both flame photometric detector (FPD) and mass spectrometry (MS) detection used for the routine quantification and identification of the residues, respectively.

Behavior of amoxicillin in wastewater and river water: identification of its main transformation products by liquid chromatography/electrospray quadrupole time-of-flight mass spectrometry.

The identification of transformation products (TPs) of pharmaceuticals in the environment is essentially a challenging task due to the lack of standards and the instrumental capabilities required to detect compounds (sometimes unknowns) that are produced under environmental conditions. In this work, we report the use of liquid chromatography/electrospray quadrupole time-of-flight mass spectrometry (LC/QTOF-MS/MS) as a tool for the identification of amoxicillin (AMX) and its main TPs in wastewater and river water samples. Laboratory degradation experiments of AMX were performed in both alkaline and acidic media in order to confirm that the expected transformation pathway in the aquatic media is through the β-lactam ring cleavage.