Application of a PLA/PBAT/Graphite sensor obtained by electrospinning on determination of 2,4,6-trichlorophenol.

The widespread use of pesticides requires effective detection and quantification tools to improve monitoring of environmental quality. Electrochemical sensors offer a fast and sensitive response, and can also be optimized by combining several constituents and techniques, including biodegradable materials, being useful in the determination of chemical agents from environmental samples. Here, we produced a polymer-based sensor for 2,4,6-trichlorophenol determination, through electrospinning of poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blend with graphite. The graphite-containing fibres were thermally treated and wetted in mineral oil, thus forming a paste, used as an electrode in the electrochemical sensor. The thermal analysis indicated a disorganization of the polymeric chains between the aromatic carbon chain of the PBAT polymer, resulting in a material with low enthalpy, lower crystallinity and greater thermal degradability after insertion of graphite in polymeric fibres. NIR spectra revealed changes related to the carbonyls of the polymeric ester groups. Cyclic voltammetry and square wave voltammetry techniques were applied to study the electrochemical behaviour of developed sensor. The thermal treatment of graphite-containing fibres increased the adhesion surface in which occurs the adsorption of the analyte on the electrode, which improved the peak current in the electrochemical tests. The PLA/PBAT/Graphite sensor applied to determination of 2,4,6-TCP presented the detection and quantification limits of 7.84 × 10-8 mol L-1 (0.0155 mg L-1) and 2.36 × 10-7 mol L-1 (0.0466 mg L-1) with a linearity response of 1.00 × 10-7 mol L-1 and 2.00 × 10-6 mol L-1 with correlation coefficient of 0.993 (r2).

Plasticizer concentration effect on films and coatings based on poly(vinyl alcohol) and cationic starch blends.

Films based on poly(vinyl alcohol) (PVA) and cationic starch (CS) were combined with different percentages of sorbitol (S; 15.0, 22.5, and 30.0% w v-1) to assess the effect of plasticizer on the films. Spectroscopic analyses confirmed the interaction between them. However, micrographs indicated the formation of sorbitol crystals on the surface of the films, especially at higher sorbitol concentrations. The blends presented low water vapor transmission rate values, reaching (7.703 ± 0.000) g h-1 m-2 (PVA75CS25S15), and low solubility values for the films containing higher CS amounts. The lack of statistical differences in most parameters suggests that no significant gain comes from increasing the amount of sorbitol at percentages higher than 15%. As a coating, the blend PVA75CS25S15 successfully decreased the loss of moisture content in acerolas by 1.15 times (compared to the control), confirming the suitability of this matrix as a fruit coating.

Electrospinning in personal protective equipment for healthcare work.

Protection in many service areas is mandatory for good performance in daily activities of workers, especially health areas. Personal protective equipment (PPE) is used to protect patients and health workers from contamination by harmful pathogens and body fluids during clinical attendance. The pandemic scenario caused by SARS-CoV-2 has shown that the world is not prepared to face global disease outbreaks, especially when it comes to the PPE of healthcare workers. In the last years, the world has faced a deficiency in the development of advanced technologies to produce high-quality PPE to attend to the exponential increasing demand. Electrospinning is a technology that can be used to produce high-quality PPE by improving the protective action of clothing. In the face of this concern, this manuscript presents as focus the potential of electrospinning to be applied in protective clothing. PPE mostly used by healthcare workers are also presented. The physico-chemical characteristics and production processes of medical textiles for PPE are addressed. Furthermore, an overview of the electrospinning technique is shown. It is important to highlight most research about electrospinning applied to PPE for health areas presents gaps and challenges; thus, future projections are also addressed in this manuscript.

Biosorption of methylene blue by residue from Lentinus crinitus mushroom cultivation.

Conventional textile effluent treatments cannot remove methylene blue, a mutagenic azo dye, and an endocrine disruptor, that remains in the drinking water after conventional water treatment. However, the spent substrate from Lentinus crinitus mushroom cultivation, a waste, could be an attractive alternative to remove persistent azo dyes in water. The objective of this study was to assess the methylene blue biosorption by spent substrate from L. crinitus mushroom cultivation. The spent substrate obtained after mushroom cultivation had been characterized by the point of zero charge, functional groups, thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. Moreover, the spent substrate biosorption capacity was determined in function of pH, time, and temperature. The spent substrate had a point of zero charge value of 4.3 and biosorbed 99% of methylene blue in pH from 3 to 9, with the highest biosorption in the kinetic assay of 15.92 mg g- 1, and in the isothermal assay of 120.31 mg g- 1. Biosorption reached equilibrium at 40 min after mixing and best fitted the pseudo-second-order model. Freundlich model best fitted the isothermal parameters and each 100 g spent substrate biosorbed 12 g dye in an aqueous solution. The spent substrate of L. crinitus cultivation is an effective biosorbent of methylene blue and an alternative to removing this dye from water, adding value to the mushroom production chain, and supporting the circular economy.

Poly(butylene adipate-co-terephthalate)/Poly(lactic acid) Polymeric Blends Electrospun with TiO2-R/Fe3O4 for Pollutant Photodegradation.

This work aimed to use the electrospinning technique to obtain PBAT/PLA polymer fibers, with the semiconductors rutile titanium dioxide (TiO2-R) and magnetite iron oxide (Fe3O4), in order to promote the photocatalytic degradation of environmental contaminants. The parameters used in the electrospinning process to obtain the fibers were distance from the needle to the collecting target of 12 cm, flow of 1 mL h-1 and voltage of 14 kV. The best mass ratio of semiconductors in the polymeric fiber was defined from a 22 experimental design, and the values obtained were 10% TiO2-R, 1% Fe3O4 at pH 7.0. Polymer fibers were characterized by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Fourier Transform Infrared (FTIR) techniques. SEM measurements indicated a reduction in fiber diameter after the incorporation of semiconductors; for the PBAT/PLA fiber, the average diameter was 0.9466 ± 0.2490 µm, and for the fiber with TiO2-R and Fe3O4 was 0.6706 ± 0.1447 µm. In the DSC, DRX, TGA and FTIR analyses, it was possible to identify the presence of TiO2-R and Fe3O4 in the fibers, as well as their interactions with polymers, demonstrating changes in the crystallinity and degradation temperature of the material. These fibers were tested against Reactive Red 195 dye, showing an efficiency of 64.0% within 24 h, showing promise for photocatalytic degradation of environmental contaminants.

Electrospun poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) nanofibers for the controlled release of cilostazol.

Drug delivery devices are attractive alternatives to drugs usually orally administrated. Therefore, this work aimed to produce PLA/PBAT-based nanofibers for the controlled release of cilostazol, evaluating the effect of different drug concentrations (20 and 30%) over the properties of the fibers. The fibers were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), x-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG/DTG), and mechanical analysis. SEM results indicated a high concentration of drug crystals on the surface of the fibers that contained 20% of cilostazol. These fibers were also thinner, more crystalline, less thermally stable, and less fragile in comparison to the fibers containing 30% of cilostazol, according to the XRD, DSC, TG/DTG, and mechanical results. The controlled release assays indicated that the fibers containing 20% of cilostazol would be attractive for short-term releases, reaching the equilibrium after approximately 6 h, while the ones containing 30% would ensure a slower release (~ 12 h). Despite the differences, both fibers would improve and enhance the efficiency of the treatment, and they would also prevent possible side effects caused by the drug to the gastric system.

Sugarcane biomass colonized by Pleurotus ostreatus for red 4B dye removal: a sustainable alternative.

Biosorption of the red 4B dye was evaluated using non-colonized sugarcane bagasse and colonized by Pleurotus ostreatus. The fungal colonization caused an increase in the acid and phenolic groups, making the biosorbent surface more positive, with lower thermal stability due to decomposition of lignocellulosic compounds, lower pHpcz, and smaller pores. The biosorbents showed better adsorption at pH 2.0 and required 260 min to reach equilibrium. The kinetic data fit the pseudo-second order mathematical model, which predicts strong chemical interaction between adsorbent and adsorbate. The mathematical models that best fit the isothermal data were the combination of Langmuir for low dye concentrations and Freundlich for high dye concentrations in the solution for the non-colonized biosorbent, which predict that adsorption occurs in monolayer and multilayer, respectively. For the colonized biosorbent, the model that best fits the isothermal data (25°C and 40°C) was the Freundlich model, showing that the adsorption for this case occurs in multilayers. Thermodynamic studies (25°C, 40°C and 50°C) show that increasing temperature decreases the biosorption capacity (exothermic process for both biosorbents), and the system shows low spontaneity with increasing concentration. Also, the entropy for non-colonized sugarcane bagasse increases at low concentrations, however after fungal colonization, it decreases for both. In industrial effluent, the non-colonized biosorbent presented a higher biosorption capacity, but fungal colonization demonstrates greater sustainability by initially allowing the production of mushrooms.

Improved antioxidant activity of a starch and gelatin-based biodegradable coating containing Tetradenia riparia extract.

The incorporation of plant-based extracts into polymer-based coatings is an efficient alternative to increase the shelf-life of stored fruit and to decrease or even prevent bacterial growth. Considering strawberries, it is also important to preserve their high antioxidant activity. Hence, this work evaluated the efficiency of a coating based on native cassava starch (NCS), gelatin, and sorbitol, containing different concentrations of Tetradenia riparia extract, in delaying the ripening process of strawberries stored under refrigerated conditions, and in preventing bacterial growth and antioxidant activity losses. Both concentrations of extract (500 or 1000 µg mL-1) increased the thickness, opacity, and water vapor transmission rate (WVTR) of the films when compared to the film without extract, but decreased the solubility. Even though the film without extract was expected to create a more efficient barrier to the coated fruits, the films containing the extract led to similar results of soluble solids (SS), titratable acidity (TA), and vitamin C. Nevertheless, the extract incorporation improved the control over bacterial growth, and preserved the high antioxidant activity of the strawberries within ten days of storage.

Shelf-life of guavas coated with biodegradable starch and cellulose-based films.

Guava is a perishable fruit susceptible to post-harvest losses. So, the development of biodegradable films based on acetylated cassava starch (ACS) and hydroxyethyl cellulose (HEC) could be an alternative to increase guavas (Psidium guajava L.) shelf life. Films were characterized by solubility, opacity, water vapor transport, and thickness. Mass loss, texture, titratable acidity, soluble solids, vitamin C, and skin color of the fruits were analyzed. The films with higher HEC concentration were more transparent and hygroscopic. Guava coated with 75% HEC and 25% ACS or 100% HEC films increased firmness, maintained green skin color and reduced ripeness, lasting for 13 days, ensuring that the ACS and HEC based films can increase guavas shelf life, besides decrease environmental impacts of non-biodegradable packages.

Effect of gelatin and casein additions on starch edible biodegradable films for fruit surface coating.

Coating fruits surface with biodegradable films obtained from starch is an alternative to delay the fruit ripening process. This study aimed to develop a biodegradable film from a polymer blend consisting of natural cassava starch, casein, and gelatin, and using sorbitol as the plasticizer. Among all the prepared biodegradable films (BFs), the one with desirable results in thickness, opacity, solubility, and water vapor transmission rate (WVTR) analyzes was based on a high concentration of starch, and casein, and low concentration of gelatin. Also, this film had the lowest solubility among all of them. Guava fruit coated with this film showed a two-day increase in shelf-life when compared to non-coated guavas. The increase in shelf-life was due to the extremely low water vapor transmission rate of the films, decreasing the fruits' mass loss, and, consequently, retarding their senescence. These results indicate that the biodegradable film is a promising material for fruit coating.

Biossorção de íons Cr(III) de soluções aquosas sintéticas e efluente de curtume utilizando a macrófita aquática Pistia stratiotes / Biosorption of Cr(III) ions from synthetic aqueous solutions and tannery effluent using the macrophyte Pistia stratiotes

RESUMO O cromo é um metal tóxico amplamente utilizado em processos industriais, por isso a constante preocupação com os efluentes líquidos gerados. Uma vez lançados sem o devido tratamento podem comprometer a qualidade do corpo receptor. Este trabalho teve por objetivo analisar o processo de biossorção na remoção de íons Cr(III) de soluções aquosas sintéticas e efluente de curtume utilizando como biossorvente a macrófita aquática Pistia stratiotes in natura (PN) e quimicamente modificada (PM) com hidróxido de sódio e ácido cítrico. Realizou-se o preparo, a caracterização dos biossorventes e os experimentos de biossorção. Os estudos de equilíbrio indicaram que a capacidade máxima de biossorção foi de 58,16 e 19,80 mg g-1 para PM e PN, respectivamente. Nos testes utilizando efluente bruto de curtume, a remoção de cromo foi de 28,26% para ambos os biossorventes, e no efluente da lagoa de tratamento biológico, a maior taxa de remoção do metal foi obtida pelo biossorvente PM, com 65,44%. Os resultados demonstraram que a utilização de P. stratiotes como biossorvente apresenta-se como uma alternativa eficaz e de baixo custo, porém estudos complementares são necessários a fim de avaliar sua aplicação em escala real.

ABSTRACT Chromium is a toxic metal widely used in industrial processes, so the concern with the liquid effluents generated is constant, that once released without proper treatment can compromise the quality of the receiver body. The study aimed at analyzing the process of biosorption in removing Cr(III) ions of synthetic aqueous solutions and tannery effluent using as biosorbent the Pistia stratiotes macrophyte in natura (PN) and chemically modified (PM) with sodium hydroxide and citric acid. The preparation, characterization of the biosorbents and the experiments of biosorption were performed. Equilibrium studies indicated that the maximum biosorption capacity for PM was 58.16 mg g-1 and 19.80 mg g-1 for PN. In the tests using raw effluent from tannery, chromium removal was 28.26% for both biosorbents, and in the effluent from biological treatment lagoon, the higher rate of metal removal was obtained by biosorbent PM with 65.44%. The results showed that the use of P. stratiotes as biosorbent may be an effective and low-cost alternative and that additional studies are needed to assess its full-scale application.

Synthesis and characterization of a low solubility edible film based on native cassava starch.

Films based on cassava starch have been widely used for fruit coating; however, it is necessary to incorporate other polymers in order to improve mechanical properties, once starch only leads to highly hydrophilic films, compromising their application. In this way, a polymeric blend based on cassava starch, chitosan and gelatin was combined with a plasticizer to produce biodegradable films with satisfactory mechanical and barrier properties, in order to be used as fruit coating. The films were prepared by casting method and a statistical design of 23 was used to evaluate the effect of each polymer and what their combinations would influence over the final product. The formation of a physical blend was confirmed by FTIR. It showed low solubility, varying (10 ±â€¯2) % a (23 ±â€¯4) %, Opacity ranging from (1.06 ±â€¯0.04) to (1.55 ±â€¯0.13) AU x nm/mm, thickness from (0.20 ±â€¯0.01) mm to (0.44 ±â€¯0.03) mm and water vapor transmission rate ranging from 25 ±â€¯0.2 to 30 ±â€¯1.4 g s-1 m-2. Lower amounts of starch led to more flexible, less opaque and soluble films, while the combination of higher levels of starch and chitosan was responsible for lowering films water vapor transmission rate. Thus, the films showed interesting properties for fruit surface coating.

Investigation on the Performance of Chemically Modified Aquatic Macrophytes-Salvinia molesta for the Micro-Solid Phase Preconcentration of Cd(II) On-Line Coupled to FAAS.

In this study, a new method for the preconcentration of cadmium ions using modified aquatic macrophytes - Salvinia molesta as biosorbent in an on-line preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed. The method is based on preconcentration of 20.0 mL sample at pH 3.75 through 35.0 mg of biosorbent at 10.0 mL min-1 and subsequent elution with 0.5 mol L-1 HNO3. A preconcentration factor of 31-fold, linear dynamic range from 5.0 to 70.0 µg L-1 (r = 0.9996) and detection and quantification limits of 0.15 and 0.51 µg L-1 were obtained. The characterization of the biosorbent chemically modified with NaOH and citric acid, was performed through FTIR and SEM measurements. The method precision was found to be 3.97 % and 1.48 % for 5.0 and 60.0 µg L-1 Cd(II) solutions, respectively. The applicability of method was checked by analysis of different kind of water samples and certified reference material.

Determinação de metais em plantas medicinais comercializadas na região de Umuarama-Pr / Determination of metals in medicinal plants commercialized in the region of Umuarama-Pr

A utilização de plantas com fins medicinais, para tratamento, cura e prevenção de doenças, é uma das mais antigas formas de prática medicinais da humanidade. Além disso, essas plantas são ricas em metais que podem ser benéficos ou não para a saúde. Desta forma, este trabalho teve como objetivo analisar amostras de plantas medicinais como a camomila (Chamomilla recutita), carqueja (Baccharis trimera), calêndula (Calendula officinalis), chapéu-de-couro (Echinodorus grandiflorus), erva-de-são-joão (Ageratum conyzoides L.) e pata-de-vaca (Bauhinia forficata), quantificando os metais zinco (Zn), ferro (Fe), cobre (Cu), chumbo (Pb), potássio (K), cromo (Cr) e níquel (Ni). As análises foram realizadas com espectrofotometria de absorção atômica com chama. Não foram detectados em nenhuma das amostras quantidades de chumbo, cromo e níquel. Constatou-se que a planta chapéu-de-couro teve os maiores valores para o metal ferro (180,16 ±7,47 mg / 100g) e potássio (3758,50 ±32,50 mg / 100g), enquanto que a pata-de-vaca se destacou em relação ao zinco (6,92 ±1,25 mg / 100g) e em média o cobre (3,81 ±0,54 mg / 100g), este fato corrobora com o valor positivo da correlação de Pearson entre estes metais. Portanto, as plantas avaliadas neste estudo podem ser consideradas uma possível fonte para suplementação dos minerais estudados, já que não foram encontradas quantidades tóxicas de metais como o chumbo, cromo e níquel.

The use of plants for medicinal purposes, treatment, cure and prevention of diseases, is one of the oldest forms of medical practice of mankind. In addition, these plants are rich in metals that can be beneficial to health or not. Thus, this study aimed to analyze samples of medicinal herbs such as chamomile (Chamomilla recutita), carqueja (Baccharis trimera), calendula (Calendula officinalis), chapéu-de-couro (Echinodorus grandiflorus), saint john? wort (Ageratum conyzoides L.) and pata-de-vaca (Bauhinia forficata), quantifying the following metals: zinc (Zn), iron (Fe), copper (Cu), lead (Pb), potassium (K), chromium (Cr) and nickel (Ni). Analyses were performed with flame atomic absorption spectrophotometry. Amounts of lead, chromium and nickel were not detected in any sample. It was found that the chapéu-de-couro plant had the highest values for iron (180.16 ± 7.47 mg / 100g) and potassium (3758.50 ± 32.50 mg / 100g); pata-de-vaca had higher values than to zinc (6.92 ± 1.25 mg / 100g) and copper (3.81 ± 0.54 mg / 100g). This corroborates the positive value of Pearson correlation between these metals. Therefore, the plants evaluated in this study can be considered a possible source for supplementing studied minerals, since there were no toxic amounts of metals such as lead, chromium and nickel.

Quantificação de minerais em sucos industrializados / Measurement of minerals inprocessed juices

Os sucos de frutas são considerados como uma boa opção de fonte de minerais e vitaminas. O consumo de sucos de frutas industrializados cresceu muito no Brasil, principalmente aqueles envasados em embalagens cartonadas da Tetra Pak®. Para avaliar o teor de minerais em sucos industrializados, foram analisadas as quantidades de sete metais (Zn, Ni, Pb, Fe, Cu, Cr e Na) em sucos de uva e pêssego (integral e light). Os minerais foram extraídos por meio da digestão com ácido clorídrico, e detectados por espectrofotometria de absorção atômica com atomização em chama. Não foram detectadas em quantidades significativas a presença dos metais Zn, Ni, Pb e Cu nos sucos. No entanto, Na, Cr e Fe foram detectados, sendo que o Cr apresentou uma concentração maior que a permitida pelas especificações da ANVISA (Agência Nacional de Vigilância Sanitária), indicando uma possível contaminação destes produtos. Vale ressaltar que o suco light de pêssego foi o que apresentou os maiores teores de ferro.

The fruit juices are considered a good option as a source of minerals and vitamins. The consumption of fruit juices has grown industrialized in Brazil, especially those packaged in cartons from Tetra Pak ®. To evaluate the content of minerals in industrialized juices were analyzed amounts of seven metals (Zn, Ni, Pb, Fe, Cu, Cr and Na) in grape juice and peach juice (integral and light). The minerals were extracted by digestion with hydrochloric acid, and detected by atomic absorption spectrometry with flame atomization. It was not detected in significant amounts to the presence of the metals Zn, Ni, Pb and Cu in the juices. However Na, Cr and Fe were detected, and Cr showed a higher concentration than allowed by the specifications of ANVISA (Agência Nacional de Vigilância Sanitária), indicating a possible contamination of these products. It is interesting to say that light peach juice showed the highest levels of iron.

Quantificação de metais pesados em peixes de um pesqueiro localizado na cidade de Umuarama PR / Quantification of heavy metals in fish from a pay fishing located in the city of Umuarama PR / Cuantificación de metales pesados en peces de un pesquero localizado en la ciudad de Umuarama PR

O objetivo deste trabalho foi quantificar os metais Pb (chumbo), Cr (cromo), Fe (ferro), Ni (níquel), Zn (zinco) e Cu (cobre) em brânquias, vísceras e musculatura da tilapia-do-Nilo (Oreochromis niloticus), lambari (Astyanax abramis), piau (Leporinus steindachneri) e catfish (Ictalurus punctatus) criados em um pesqueiro na região de Umuarama-Paraná. As medidas foram realizas em triplicata, empregando-se espectrofotometria de absorção atômica em chama (ar-acetileno) (GBC 932 plus). A quantidade dos metais chumbo, cromo, níquel estiveram abaixo dos limites estabelecidos pela ANVISA (2; 0,1; 5 mgkg-1, respectivamente). Entretanto, a quantidade de cobre nas vísceras do piau (40,4 mgkg-1) estava acima dos valores preconizados (30 mgkg-1), indicando uma possível contaminação deste peixe. O zinco foi o que apresentou concentrações mais preocupantes, ou seja, maiores que as quantidades indicadas para o consumo (50 mgkg-1), principalmente nas vísceras e brânquias, partes consideradas não comestíveis. Entretanto, foi o único metal que apresentou valores acima do tolerado na musculatura (parte comestível) da tilápia e do lambari (55,1 e 73,7 mgkg-1, respectivamente), indicando que este peixe estaria impróprio para o consumo humano. As maiores concentrações foram encontradas para o mineral ferro, porém, como não possui limites máximos estipulados, não se pode afirmar que estaria em quantidades inadequadas ao consumo.

The objective of this study was to quantify the Pb (lead), Cr (Chromium), Fe (Iron), Ni (Nickel), Zn (Zinc) and Cu (Copper) in gills, viscera and muscle of tilapia (Oreochromis niloticus), lambari (Astyanax abramis), piau (Leporinus steindachneri) and catfish (Ictalurus punctatus) created in a pay fishing in the region of Umuarama-Paraná. Measurements were taken in triplicate, using atomic absorption spectrophotometer in flame (air-acetylene) (GBC 932 plus). The quantity of lead, chromium and nickel were below the limits set by ANVISA (2, 0.1, 5 mg kg-1, respectively). However, the amount of copper in the viscera of piau (40.4 mg kg-1) was above the recommended (30 mg kg-1), indicating possible contamination. Zinc was presented in the highest concentration, i.e., higher than the amounts indicated for consumption (50 mg kg-1), mainly in the viscera and gills – parts considered inedible. However, it was the only metal that showed values above the tolerated in the muscle (edible part) of tilapia and lambari (55.1 and 73.7 mgkg-1, respectively), indicating that this fish was improper for human consumption. The highest concentrations were found for the Iron, However as there are no limits established, it cannot be assume not to be suitable for consumption.

El objeto de esta investigación fue cuantificar los metales Pb (plomo), Cr (cromo), Fe (hierro), Ni (níquel), Zn (cinc) y Cu (cobre) en branquias, víscera y musculatura de Tilapia del Nilo (Oreochromis niloticus), Lambari, (Astyanax abramis), Piau (Leporinus steindachneri) y catfish (Ictalurus punctatus) creados en un pesquero de la región de Umuarama-Paraná. Las medidas fueron realizadas en triplicidad, empleándose espectrofotometría de absorción atómica en llama (aire- acetileno) (GBC 932 plus). La cantidad de los metales plomo, cromo, níquel etuvierom abajo de los límites establecidos por la ANVISA (2; 0,1; 5 mgkg¹, respectivamente). Sin embargo, la cantidad de cobre en las vísceras del piau (40,4 mgkg¹) estaba arriba de los valores preconizados (30 mgkg¹), indicando una posible contaminación de este pez. El cinc fue el que presentó concentraciones más preocupantes, o sea, mayores que las cantidades indicadas para el consumo (50 mgkg¹), principalmente en las vísceras y branquias, partes consideradas no comestibles. El cinc fue el único metal que presentó valores arriba del tolerado en la musculatura (parte comestible) de tilápia y lambari (55,1 y 73,7 mgkg¹), respectivamente, indicando que este pescado estaría impropio para el consumo humano. Las mayores concentraciones fueron encontradas para el mineral hierro, pero como no hay límites máximos estipulados, no se puede afirmar que estaría en cantidades inadecuadas al consumo.

Determination of Parathion and Carbaryl Pesticides in Water and Food Samples Using a Self Assembled Monolayer /Acetylcholinesterase Electrochemical Biosensor.

An acetylcholinesterase (AchE) based amperometric biosensor was developed by immobilisation of the enzyme onto a self assembled modified gold electrode. Cyclic voltammetric experiments performed with the SAM-AchE biosensor in phosphate buffer solutions (pH = 7.2) containing acetylthiocholine confirmed the formation of thiocholine and its electrochemical oxidation at Ep = 0.28 V vs Ag/AgCl. An indirect methodology involving the inhibition effect of parathion and carbaryl on the enzymatic reaction was developed and employed to measure both pesticides in spiked natural water and food samples without pre-treatment or pre-concentration steps. Values higher than 91-98.0% in recovery experiments indicated the feasibility of the proposed electroanalytical methodology to quantify both pesticides in water or food samples. HPLC measurements were also performed for comparison and confirmed the values measured amperometrically.