Distribution of organochlorine, organophosphates, carbamate, thiocarbamate, pyrethroids, and strobilurins in surface sediments of the Rio de Ondas watershed by GC-MS.

The determination of some pesticides in surface sediments can provide important information about their distribution in the water column. This work aimed to determine the distribution of the classes of pesticides along the Ondas River's hydrographic basin (ORHB), in eighteen different points, during the dry and rainy periods. The pesticides were extracted from the sediment samples by solid-liquid extraction and then analyzed using a gas chromatograph coupled to mass spectrometry. After the development and validation of the method, nineteen pesticides from the group of organochlorine, organophosphates, carbamate and thiocarbamate, pyrethroids, and strobilurins were quantified in at least one point in the two collection periods, with accuracy varying between 86 and 126%. The average concentrations were 0.020 ng g-1 (carbofuran) to 249.123 ng g-1 (dimethoate) and 0.029 ng g-1 (carbofuran and sulfotep) to 533.522 ng g-1 in the dry and rainy periods, respectively. The results showed a wide distribution of pesticide residues in the ORHB, with higher levels for dimethoate, phenitrothion, and malathion, which may be related to their agricultural use in the region. In Brazil, it does not have specific legislation for maximum permitted values of pesticides in sediment, allowing for inappropriate or prohibited use and, consequently, affecting water quality.

Determination of Carbamates and Thiocarbamates in Water, Soil and Sediment of the Formoso River, TO, Brazil.

Considering the increase in agricultural production in Brazil, the use of pesticides for this production, and that there are no studies on pesticides in the region, the presence of carbamates and thiocarbamates was investigated in different environmental compartments of the Formoso River, TO, Brazil, by UHPLC/MS/MS. The collections were made on the banks of this river, in the area of influence of the agricultural project. The active principles were not found in the soil and sediment samples, only the propoxur principle was found in the water, reaching values of up to 0.025 µg L-1 . It was found that the biodiversity of the Tocantinense savannah is under threat, because even though only one of the substances surveyed, propoxur and its derivatives, has been detected, they are substances of high toxicity and tendency to contaminate surface and groundwater to varying degrees and irreversible damage to different species.

Inorganic selenium speciation analysis in Allium and Brassica vegetables by ionic liquid assisted liquid-liquid microextraction with multivariate optimization.

A highly sensitive vortex assisted liquid-liquid microextraction (VA-LLME) method was developed for inorganic Se [Se(IV) and Se(VI)] speciation analysis in Allium and Brassica vegetables. Trihexyl(tetradecyl)phosphonium decanoate phosphonium ionic liquid (IL) was applied for the extraction of Se(IV)-ammonium pyrrolidine dithiocarbamate (APDC) complex followed by Se determination with electrothermal atomic absorption spectrometry. A complete optimization of the graphite furnace temperature program was developed for accurate determination of Se in the IL-enriched extracts and multivariate statistical optimization was performed to define the conditions for the highest extraction efficiency. Significant factors of IL-VA-LLME method were sample volume, extraction pH, extraction time and APDC concentration. High extraction efficiency (90%), a 100-fold preconcentration factor and a detection limit of 5.0ng/L were achieved. The high sensitivity obtained with preconcentration and the non-chromatographic separation of inorganic Se species in complex matrix samples such as garlic, onion, leek, broccoli and cauliflower, are the main advantages of IL-VA-LLME.

Shiga-like toxin B subunit of Escherichia coli as scaffold for high-avidity display of anti-immunocomplex peptides.

Small compounds cannot bind simultaneously to two antibodies, and thus, their immunodetection is limited to competitive formats in which the analyte is indirectly quantitated by measuring the unoccupied antibody binding sites using a competing reporter. This limitation can be circumvented by using phage-borne peptides selected for their ability to specifically react with the analyte-antibody immunocomplex, which allows the detection of these small molecules in a noncompetitive format (PHAIA) with increased sensitivity and a positive readout. In an effort to find substitutes for the phage particles in PHAIA, we explore the use of the B subunit of the Shiga-like toxin of Escherichia coli, also known as verotoxin (VTX), as a scaffold for multivalent display of anti-immunocomplex peptides. Using the herbicides molinate and clomazone as model compounds, we built peptide-VTX recombinant chimeras that were produced in the periplasmic space of E. coli as soluble pentamers, as confirmed by multiangle light scattering analysis. These multivalent constructs, which we termed nanopeptamers, were conjugated to a tracer enzyme and used to detect the herbicide-antibody complex in an ELISA format. The VTX-nanopeptamer assays performed with over a 10-fold increased sensitivity and excellent recovery from spiked surface and mineral water samples. The carbon black-labeled peptide-VTX nanopeptamers showed great potential for the development of a lateral-flow test for small molecules with a visual positive readout that allowed the detection of up to 2.5 ng/mL of clomazone.

Nanopeptamers for the development of small-analyte lateral flow tests with a positive readout.

There is a great demand for rapid tests that can be used on-site for the detection of small analytes, such as pesticides, persistent organic pollutants, explosives, toxins, medicinal and abused drugs, hormones, etc. Dipsticks and lateral flow devices, which are simple and provide a visual readout, may be the answer, but the available technology for these compounds requires a competitive format that loses sensitivity and produces readings inversely proportional to the analyte concentration, which is counterintuitive and may lead to potential misinterpretation of the result. In this work, protein-multipeptide constructs composed of anti-immunocomplex peptides selected from phage libraries and streptavidin/avidin as core protein were used for direct detection of small compounds in a noncompetitive two-site immunoassay format that performs with increased sensitivity and positive readout. These constructs that we termed "nanopeptamers" allow the development of rapid point-of-use tests with a positive visual end point of easy interpretation. As proof of concept, lateral flow assays for the herbicides molinate and clomazone were developed and their performance was characterized with field samples.

Ultra-sensitive electrochemical immunosensor using analyte peptidomimetics selected from phage display peptide libraries.

Immunosensors for small analytes have been a great addition to the analytical toolbox due to their high sensitivity and extended analytical range. In these systems the analyte is detected when it competes for binding to the detecting antibody with a tracer compound. In this work we introduce the use of phage particles bearing peptides that mimic the target analyte as surrogates for conventional tracers. As a proof of concept, we developed a magneto-electrochemical immunosensor (EI) for the herbicide molinate and compare its performance with conventional formats. Using the same anti-molinate antibody and phage particles bearing a molinate peptidomimetic, the EI performed with an IC(50) of 0.15 ngmL(-1) (linear range from 4.4 × 10(-3) to 10 ngmL(-1)). Compared to the conventional ELISA, the EI was faster (minutes), performed with a much wider linear range, and the detection limit that was 2500-fold lower. The EI produced consistent measurements and could be successfully used to assay river water samples with excellent recoveries. By using the same EI with a conventional tracer, we found that an important contribution to the gain in sensitivity is due to the filamentous structure of the phage (9 × 1000 nm) which works as a multienzymatic tracer, amplifying the competitive reaction. Since phage-borne peptidomimetics can be selected from phage display libraries in a straightforward systematic manner and their production is simple and inexpensive, they can contribute to facilitate the development of ultrasensitive biosensors.

Determination of thiodicarb using a biosensor based on alfalfa sprout peroxidase immobilized in self-assembled monolayers.

A biosensor based on alfalfa sprout (Medicago sativa) homogenate as a source of peroxidase is proposed for the determination of thiodicarb by square-wave voltammetry. This enzyme was immobilized in self-assembled monolayers of l-cysteine on a gold electrode. Several parameters were investigated to evaluate the optimum conditions for operation of the biosensor. The analytical curve was linear for thiodicarb concentrations of 2.27 x 10(-6) to 4.40 x 10(-5) mol L(-1) with a detection limit of 5.75 x 10(-7) mol L(-1). The lifetime of the Au-alfalfa sprout-SAMs was 20 days (at least 220 determinations). The average recovery of thiodicarb from samples of vegetable extracts ranged from 99.02 to 101.04%. The results obtained for thiodicarb in vegetable extracts using the proposed method are in close agreement with those using a high performance liquid chromatography procedure at the 95% confidence level.

Dietary exposure of Brazilian consumers to dithiocarbamate pesticides--a probabilistic approach.

A probabilistic estimation of the exposure of the Brazilian population to the dithiocarbamate pesticides was performed using the Monte Carlo Risk Assessment program (MCRA 3.5). Residue data, as CS2, for 3821 samples were obtained from the Brazilian national monitoring program on pesticide residues and from the monitoring program conducted in the Distrito Federal on rice, beans and nine fruits and vegetables. Food consumption data were obtained from a Brazilian household budget survey conducted between 2002 and 2003. Processing factors for washing, peeling or cooking were applied to the residues found in the crops. Daily intakes at the highest percentiles for the general population reached a maximum of 2.0 microg CS2/kg body weight per day (upper band of the 95% confidence interval at P99.99). Tomato, rice, apple and lettuce were the commodities which contributed most to the intake. Based on the registered uses and the toxicological profile of dithiocarbamates, the risk from exposure was evaluated assuming that all residues came from the use of ethylene-bis-dithiocarbamate (EBDC) or that a fraction of it came from the use of propineb. For this last scenario, a cumulative risk assessment was conducted. In the first scenario, the highest intake reached up to 11.9% EBDC ADI for the general population and up to 31.1% ADI for children. When 30% of the residues were considered as coming from propineb use, the values were 15.2% and 39.7% ADI, respectively.

Robust and sensitive monoclonal enzyme-linked immunosorbent assay for the herbicide molinate.

This paper reports on the generation of monoclonal antibodies and the development of a new enzyme-linked immunosorbent assay (ELISA) for the detection of molinate (S-ethyl hexahydroazepine-1-carbothioate). Hybridoma cells were generated using spleen and lymph node cells from a mouse immunized with S-2-carboxyethyl hexahydroazepine-1-carbothioate conjugated to keyhole limpet hemocyanin. After screening with a competitive ELISA, two monoclonal antibodies, mAbs 16C11 and 14D7, with IC(50) values of 82 +/- 2 and 173 +/- 8 ng/mL, respectively, were selected. MAb 16C11 can detect molinate concentrations of 1 ng/mL with no cross-reactivity to any other thiocarbamate pesticides; however, it was susceptible to the presence of organic solvents and to variation in buffer ionic strength. MAb 14D7 tolerated concentrations up to 5% of propylene glycol and 12.5% of acetonitrile in the assay buffer. The sensitivity of mAb 14D7 was further improved by decreasing the amount of coating antigen in the ELISA; the final inhibition assay showed an IC(50) of 69.2 +/- 1.4 ng/mL. In summary, mAb14D7 provided a more sensitive and robust assay, as compared with previous polyclonal antibody-based assays, with the additional advantage of being based upon a consistent and unlimited source of a defined reagent.

Multianalyte determination of different classes of pesticides (acidic, triazines, phenyl ureas, anilines, organophosphates, molinate and propanil) by liquid chromatography-electrospray-tandem mass spectrometry.

This work describes the optimization of a liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS-MS) method for the multianalyte determination of twenty pesticides, selected based on current regulations and extent of use. Chromatographic separation was carried out on a Purospher STAR RP-18e column using gradient acetonitrile-water as mobile phase. Triazines, phenylureas, organophosphates, anilines, and molinate were determined in the positive ionization mode, and acidic pesticides and propanil in the negative ion mode. Two different precursor ion-product ion transitions were selected for each analyte and monitored under time scheduled multiple reaction monitoring (MRM) conditions. The optimized method was shown to be linear in the range 1 to 1000 ng/mL with correlation coefficients higher than 0.99 for all but one (diazinon) of the analytes, very sensitive (with limits of detection between 0.010 and 4.528 ng/mL), and repeatable (with relative standard deviations, calculated from the replicate analysis of standard mixtures, lower than 14%). The present work was also devoted to the elucidation of the structures of the principal fragment ions obtained after collision-induced dissociation of the pesticides investigated, an aspect often overlooked in the literature.