Monitorização de pesticidas em águas de Esposende

De forma a proteger o ambiente e a saúde humana, é imperativo evitar, prevenir ou reduzir as concentrações prejudiciais de poluentes nocivos na água subterrânea. A necessidade da obtenção de níveis de protecção da água subterrânea, encontra-se estabelecida em normas de qualidade e devem ser desenvolvidas metodologias que permitam a avaliação do estado químico da água subterrânea. Este trabalho experimental centrou-se no desenvolvimento de uma metodologia analítica de detecção e quantificação por cromatografia gasosa com detector de captura de electrões dos pesticidas atrazina e respectivos metabolitos (desetilatrazina e deisopropilatrazina), simazina, terbutilazina e o metabolito desetiterbutilazina, folpete, dimetoato, diazinão, malatião, cloropirifos e o azinfos-metilo em águas de poços. O estudo progressivo baseou-se na colheita de água a 20 poços agrícolas na zona de Esposende, área considerada pelo Ministério da Agricultura do Desenvolvimento Rural e Pescas como sendo uma zona vulnerável. O método utilizado para a validação da técnica cromatográfica baseou-se na norma ISO 8466-1:1990. Os parâmetros de validação considerados foram: especificidade/selectividade, capacidade de identificação, limites de detecção e quantificação, relação sinal/ruído, linearidade e curva de calibração, precisão (repetibilidade, precisão intermédia e reprodutibilidade), eficiência de extracção e arrastamento. O método demonstrou ser capaz de identificar e quantificar os analitos, sem interferência de outros compostos. Obteve-se um valor para os parâmetros da precisão inferior a 10%, enquanto os mais baixos limites de detecção e de quantificação foram, respectivamente, 0,014 e 0,047 μg L-1. Na preparação de amostras optou-se pelo método de extracção em fase sólida, tendo sido testadas cinco diferentes tipos de colunas extractivas; Lichrolut® EN/RP-18; Strata SDB-L e C18-E; Chromabond HR-P e HR-X, sendo que as colunas Lichrolut® EN/RP- 18 apresentaram melhores resultados para a globalidade dos pesticidas. Da análise efectuada aos 20 poços agrícolas verificou-se que apenas 3 não apresentavam qualquer vestígio dos pesticidas monitorizados, sendo que as restantes apresentavam valores entre 0,05 e 53,2 μg L-1, valores superiores aos impostos pela legislação em vigor (Decreto-Lei n.º 208/2008 de 28 de Outubro para água subterrânea e Decreto-Lei nº306/2007 referente a água para consumo). Verificou-se que os proprietários dos poços agrícolas, dos quais se procedeu à amostragem de água para análise não têm a consciência da falta de qualidade dessa água, nem dos malefícios que possam advir do seu consumo.

Monitorização de desreguladores endócrinos em águas

Da crescente necessidade de alimentos e da necessidade de travar a destruição de culturas por animais e insectos foram sintetizados os pesticidas. Por entre uma vasta gama de pesticidas alguns são desreguladores endócrinos o que se traduz num perigo para a saúde humana pois pode despoletar alterações nos seres vivos mesmo em concentrações muito baixas. Devido a diversos factores nomeadamente a lixiviação, ventos e outros agentes ambientais assim como a presença de terrenos agrícolas junto a diversos rios, estes encontram-se contaminados com pesticidas desreguladores endócrinos. O objectivo deste trabalho foi avaliar quais os pesticidas desreguladores endócrinos presentes nas águas de rios da região Norte. Neste trabalho utilizou-se a técnica de microextracção em fase sólida recorrendo a uma fibra de PDMS (100 μm). Para tal as condições de optimização foram testadas nomeadamente a quantidade de NaCl, quantidade de metanol, temperatura do injector e tempo de exposição. Os parâmetros obtidos óptimos foram 0 % de NaCl, tempo de exposição de 45 min, temperatura do injector de 260 ºC e 2,5 % de metanol. Conseguiu-se a separação de todos os pesticidas desreguladores endócrinos com a seguinte programação temperaturas: inicio a 60ºC por um minuto seguido de um aumento de 20 °C/min até aos 200 °C onde permanece por um minuto e de seguida um aumento de 5 °C/min até aos 245 °C onde permanece por 40 min. Fizeram-se curvas de calibração entre 0,01 μg/L e 10 μg/L. Constatou-se no entanto uma falta de reprodutibilidade entre as injecções utilizando esta técnica. Os rios analisados foram o Rio Douro, Rio Tâmega, Ria de Aveiro, Rio Lima, Rio Minho, Rio Sousa, Rio Águeda, Rio Cávado e Rio Leça. No Rio Tâmega foram encontrados os seguintes pesticidas: diazinão, α-HCH, β-HCH, δ-HCH, lindano, HCB, simazina/ atrazina, vinclozolina, alacloro, 2,4-D, malatião, aldrina, bifentrina, metoxicloro e fenvalerato. No rio Douro estão presentes HCB, simazina/ atrazina, vinclozolina, 2,4-D, malatião, aldrina, fenvalerato e deltametrina. No rio Lima encontra-se diazinão, α-HCH, δ-HCH, 2,4-D, HCB, vinclozolina, lindano, simazina/atrazina, alacloro, malatião, aldrina, fenvalerato e deltametrina. No rio Sousa os pesticidas encontrados foram: diazinão, HCB, aldrina, α-HCH, β-HCH, δ-HCH, lindano, simazina/ atrazina, 2,4-D, cipermetrina, alacloro, fenvalerato e malatião. No rio Cávado estão presentes o diazinão, α-HCH, β-HCH, δ-HCH, lindano, HCB, 2,4-D, malatião, metoxicloro, cipermetrina e o fenvalerato. Na ria de Aveiro encontrou-se o diazinão, α-HCH, β-HCH, δ-HCH, lindano, HCB, simazina/atrazina, 2,4-D, Malatião e aldrina. No rio Águeda estão presentes o diazinão, HCB, 2,4-D, aldrina e malatião. E por último no rio Leça esta presente o diazinão, 2,4-D, alacloro, malatião, aldrina, cipermetrina e fenvalerato. A importância deste trabalho reside na demonstração da presença destes pesticidas, desreguladores endócrinos nas águas superficiais da região Norte.

Contaminação ambiental por pesticidas: análise metodológica

Este trabalho teve como objectivo pesquisar os pesticidas que são mais usados em Portugal, os métodos de análise mais frequentemente utilizados na determinação de pesticidas, a contaminação ambiental por pesticidas e como minimizar o impacto ambiental provocado pelo uso indiscriminado de pesticidas. Os pesticidas usados variam de acordo com as diferentes características das regiões de Portugal e os grupos de pesticidas mais usados são: organofosforados, derivados de anilina, derivados triazinicos, tiocarbamatos, derivados do ácido fenoxiacético, derivados de acetamida, benzotiadiazole, derivados de ureia e azol. A determinação destes grupos é usualmente feita usando métodos cromatográficos, uma vez que estes métodos permitem a separação de misturas complexas. A contaminação ambiental por pesticidas pode ser provocada por diversos factores, contudo esta contaminação pode ser minimizada se estes forem usados de forma racional e de um modo sustentável conforme o descrito na directiva 2009/128/CE de 21 de Outubro.

Flow amperometric determination of carbofuran and fenobucarb

A simple, rapid, and precise amperometric method for quantification of N-methylcarbamate pesticides in water samples and phytopharmaceuticals is presented. Carbofuran and fenobucarb are the target analytes. The method is developed in flow conditions providing the anodic oxidation of phenolic-based compounds formed after alkaline hydrolysis. Optimization of instrumental and chemical variables is presented. Under the optimal conditions, the amperometric signal is linear for carbofuran and fenobucarb concentrations over the range of 1.0*10-7 to 1.0*10-5 molL-1, with a detection limit of about 2 ngmL-1. The amperometric method is successfully applied to the analysis of spiked environmental waters and commercial formulations. The proposed method allows 90 samples to be analysed per hour, using 500 mL of sample, and producing wastewaters of low toxicity. The proposed method permits determinations at the mgL 1 level and offers advantages of simplicity, accuracy, precision, and applicability to coloured and turbid samples, and automation feasibility.

Determination of carbamate and urea pesticide residues in fresh vegetables using microwave-assisted extraction and liquid chromatography

An analytical multiresidue method for the simultaneous determination of seven pesticides in fresh vegetable samples, namely, courgette (Cucurbita pepo), cucumber (Cucumis sativus), lettuce (Lactuca sativa, Romaine and Iceberg varieties) and peppers (Capsicum sp.) is described. The procedure, based on microwave-assisted extraction (MAE) and analysis by liquid chromatography– photodiode array (LC–PDA) detection was applied to four carbamates (carbofuran, carbaryl, chlorpropham and EPTC) and three urea pesticides (monolinuron, metobromuron and linuron). Extraction solvent and the addition of anhydrous sodium sulphate to fresh vegetable homogenate before MAE were the parameters optimised for each commodity. Recovery studies were performed using spiked samples in the range 250–403 µgkg- 1 in each pesticide. The pesticide residues were extracted using 20mL acetonitrile at 60 ºC, for 10 min. Acceptable recoveries and RSDs were attained (overall average recovery of 77.2% and RSDs are lower than 11%). Detection limits ranged between 5.8 µgkg- 1 for carbaryl to 12.3 µgkg- 1 for carbofuran. The analytical protocol was applied for quality control of 41 fresh vegetable samples bought in Oporto Metropolitan Area (North Portugal). None of the samples contained any detectable amounts of the studied compounds.

Screening of carbamates and ureas in fresh and processed tomato samples using micowave-assisted extraction and liquid chromatography

An analytical method, based on microwave-assisted extraction and liquid chromatography with diode array detection, for the determination of six carbamate and three urea pesticides in fresh and processed tomato samples is described. Significant parameters affecting extraction efficiency were optimized. Under optimum microwave-assisted extraction conditions (20mL acetonitrile, for 10 minutes, at 60º C), pesticides were extracted with recoveries ranging from 57.6 to 102% (RSDs<7%). Quantification limits between 6.5 and 39.6 µg=kg were obtained. A total number of 28 different fresh tomato samples and 6 processed tomato products were analysed. Confirmation of suspicious samples was performed by LC-MS.

Use and reuse of SPE disks for the determination of pyrethroids in water by GC-ECD

Seven pyrethroids (bifenthrin, fenpropathrin, k-cyhalothrin, permethrin, a-cypermethrin, fenvalerate, and deltamethrin) were extracted from water using C18 solid-phase extraction disks, followed by gas chromatography with an electron capture detector (GC-ECD) analysis. The limits of detection in water samples ranged from 0.5 ng L-1 (fenpropathrin) to 110 ng L- 1 (permethrin), applying the calibration graph. The effects of different numbers of (re)utilizations of the same disks (up to four times with several concentrations) on the recoveries of the pyrethroids were considered. The recoveries were all between 70 and 120% after four utilizations of the same disk. There was no difference between these recoveries at a confidence level of 95%.

Sorption behaviour of bifenthrin on cork

Biphentrin, a known pyrethroid, was studied, aiming its removal from aqueous solutions by granulated cork sorption. Batch experiments, either for equilibrium or for kinetics, with two granulated cork sizes were performed and results were compared with those obtained with of activated carbon sorption. Langmuir and Freundlich adsorption isotherms were obtained both showing high linear correlations. Bifenthrin desorption was evaluated for cork and results varied with the granule size of sorbent. The results obtained in this work indicate that cork wastes may be used as a cheap natural sorbent for bifenthrin or similar compounds removal from wastewaters.

Amperometric and spectrophotometric determination of carbaryl in natural waters and commercial formulations

The work presented describes the development and evaluation of two flow-injection analysis (FIA) systems for the automated determination of carbaryl in spiked natural waters and commercial formulations. Samples are injected directly into the system where they are subjected to alkaline hydrolysis thus forming 1-naphthol. This product is readily oxidised at a glassy carbon electrode. The electrochemical behaviour of 1-naphthol allows the development of an FIA system with an amperometric detector in which 1-naphthol determination, and thus measurement of carbaryl concentration, can be performed. Linear response over the range 1.0×10–7 to 1.0×10–5 mol L–1, with a sampling rate of 80 samples h–1, was recorded. The detection limit was 1.0×10–8 mol L–1. Another FIA manifold was constructed but this used a colorimetric detector. The methodology was based on the coupling of 1-naphthol with phenylhydrazine hydrochloride to produce a red complex which has maximum absorbance at 495 nm. The response was linear from 1.0×10–5 to 1.5×10–3 mol L–1 with a detection limit of 1.0×10–6 mol L–1. Sample-throughput was about 60 samples h–1. Validation of the results provided by the two FIA methodologies was performed by comparing them with results from a standard HPLC–UV technique. The relative deviation was <5%. Recovery trials were also carried out and the values obtained ranged from 97.0 to 102.0% for both methods. The repeatability (RSD, %) of 12 consecutive injections of one sample was 0.8% and 1.6% for the amperometric and colorimetric systems, respectively.

Chlormequat selective electrodes: construction, evaluation and application at FIA systems

A flow injection analysis (FIA) system having a chlormequat selective electrode is proposed. Several electrodes with poly(vinyl chloride) based membranes were constructed for this purpose. Comparative characterization suggestedthe use of membrane with chlormequat tetraphenylborate and dibutylphthalate. On a single-line FIA set-up, operating with 1x10-2 mol L-1 ionic strength and 6.3 pH, calibration curves presented slopes of 53.6±0.4mV decade-1 within 5.0x10-6 and1.0x10-3 mol L-1, andsquaredcorrelation coefficients >0.9953. The detection limit was 2.2x10-6 mol L-1 and the repeatability equal to ±0.68mV (0.7%). A dual-channel FIA manifold was therefore constructed, enabling automatic attainment of previous ionic strength andpH conditions and thus eliminating sample preparation steps. Slopes of 45.5±0.2mV decade -1 along a concentration range of 8.0x10-6 to 1.0x10-3 mol L-1 with a repeatability ±0.4mV (0.69%) were obtained. Analyses of real samples were performed, and recovery gave results ranging from 96.6 to 101.1%.

Determination of 24 pesticide residues in fortified wines by solid-phase microextraction and gas chromatography tandem mass spectrometry

The present work describes a solid-phase microextraction (SPME) gas chromatography_tandem mass spectrometry (MS/MS) method to quantify 24 pesticides in fortified white wine and fortified red wine. In this study “fortified wine” refers to a wine in which fermentation is arrested before completion by alcohol distillate addition, allowing sugar and alcoholic contents to be higher (around 80-100 g/L total sugars and 19-22% alcohol strength (v/v)). The analytical method showed good linearity, presenting correlation coefficients (R2) ≥ 0.989 for all compounds. Limits of detection (LOD) and quantitation (LOQ) in the ranges of 0.05-72.35 and 0.16-219.23 μg/L, respectively, were obtained. LOQs are below the maximum residue levels (MRL) set by European Regulation for grapes. The proposed method was applied to 17 commercial fortified wines. The analyzed pesticides were not detected in the wines tested.

Organochlorine pesticide residues in strawberries from integrated pest management and organic farming

A rapid, specific, and sensitive method based on theQuick Easy Cheap Effective Rugged and Safe (QuEChERS) method and a cleanup using dispersive solid-phase extraction with MgSO4, PSA, and C18 sorbents has been developed for the routine analysis of 14 pesticides in strawberries. The analyses were performed by three different analytical methodologies: gas chromatography (GC) with electron capture detection (ECD), mass spectrometry (MS), and tandem mass spectrometry (MS/MS). The recoveries for all the pesticides studied were from 46 to 128%, with relative standard deviation of <15% in the concentration range of 0.005-0.250 mg/kg. The limit of detection (LOD) for all compoundsmetmaximumresidue limits (MRL) accepted in Portugal for organochlorine pesticides (OCP). A survey study of strawberries produced in Portugal in the years 2009-2010 obtained from organic farming (OF) and integrated pest management (IPM) was developed. Lindane and β-endosulfan were detected above the MRL in OF and IPM. Other OCP (aldrin, o,p0-DDT and their metabolites, and methoxychlor) were found below the MRL. The OCP residues detected decreased from 2009 to 2010. The QuEChERS method was successfully applied to the analysis of strawberry samples.

Determination of methiocarb and Its degradation products, methiocarb sulfoxide and methiocarb sulfone, in bananas using QuEChERS extraction

The present work describes the development of an analytical method for the determination of methiocarb and its degradation products (methiocarb sulfoxide and methiocarb sulfone) in banana samples, using the QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure followed by liquid chromatography coupled to photodiode array detector (LCPAD). Calibration curves were linear in the range of 0.5−10 mg L−1 for all compounds studied. The average recoveries, measured at 0.1 mg kg−1 wet weight, were 92.0 (RSD = 1.8%, n = 3), 84.0 (RSD = 3.9%, n = 3), and 95.2% (RSD = 1.9%, n = 3) for methiocarb sulfoxide, methiocarb sulfone, and methiocarb, respectively. Banana samples treated with methiocarb were collected from an experimental field. The developed method was applied to the analysis of 24 samples (peel and pulp) and to 5 banana pulp samples. Generally, the highest levels were found for methiocarb sulfoxide and methiocarb. Methiocarb sulfone levels were below the limit of quantification, except in one sample (not detected).

Optimization of QuEChERS procedure coupled to GC-ECD for organochlorine pesticide determination in carrot samples

An optimised version of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for simultaneous determination of 14 organochlorine pesticides in carrots was developed using gas chromatography coupled with electron-capture detector (GC-ECD) and confirmation by gas chromatography tandem mass spectrometry (GC-MS/MS). A citrate-buffered version of QuEChERS was applied for the extraction of the organochlorine pesticides, and for the extract clean-up, primary secondary amine, octadecyl-bonded silica (C18), magnesium sulphate (MgSO4) and graphitized carbon black were used as sorbents. The GC-ECD determination of the target compounds was achieved in less than 20 min. The limits of detection were below the EUmaximum residue limits (MRLs) for carrots, 10–50 μg kg−1, while the limit of quantification did exceed 10 μg kg−1 for hexachlorobenzene (HCB). The introduction of a sonication step was shown to improve the recoveries. The overall average recoveries in carrots, at the four tested levels (60, 80, 100 and 140 μg kg−1), ranged from 66 to 111% with relative standard deviations in the range of 2– 15 % (n03) for all analytes, with the exception of HCB. The method has been applied to the analysis of 21 carrot samples from different Portuguese regions, and β-HCH was the pesticide most frequently found, with concentrations oscillating between less than the limit of quantification to 14.6 μg kg−1. Only one sample had a pesticide residue (β-HCH) above the MRL, 14.6 μg kg−1. This methodology combines the advantages of both QuEChERS and GC-ECD, producing a very rapid, sensitive and reliable procedure which can be applied in routine analytical laboratories.

Photostabilization of phenoxyacetic acid herbicides MCPA and mecoprop by hydroxypropyl-β-cyclodextrin

New strategies to reduce the environmental and economic costs of pesticides use are currently under study. Microencapsulation has been used as a versatile tool for the production of controlled release agricultural formulations. In this study, the photochemical degradation of the herbicides MCPA and mecoprop has been investigated in different aqueous media such as ultrapure and river water under simulated solar irradiation. To explore the possibility of introducing cyclodextrins in the herbicide formulations, the photodegradation study of the inclusion complexes of MCPA and mecoprop with (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) was also performed. The half-lives of MCPA and mecoprop inclusion complexes were increased approximately by a factor of three related to the free molecules. Additionally, it has been shown that the photodegradation of MCPA and mecoprop is influenced by their structural features. The additional methyl group existing in mecoprop molecular structure has a positive influence on the stabilization of the radical intermediate formed in the first stage of photodegradation of both herbicides. The results found indicated that MCPA and mecoprop form inclusion complexes with HP-β-CD showing higher photostability compared to free herbicides indicating that HP-β-CD may serve as ingredient in these herbicide formulations.