Optimizing microwave-assisted solvent extraction (MASE) of pesticides from soil

Application of Deconica castanella ligninolytic enzymatic system in the degradation of hexachlorobenzene in soil

Hexachlorobenzene (HCB) is a pollutant still found in the environment despite being widely banned. Considering that basidiomycetes are useful to degrade a variety of organochlorinated pollutants, we therefore report the influence of HCB on the ligninolytic enzymatic system of Deconica castanella. The inoculum was prepared with sugarcane bagasse and soybean flour and was added in soil with and without HCB (2000 mg kg soil^-1 ), 5% emulsion containing soybean oil and Tween 20 at proportion 9:1, v:v; with 70% moisture at 25°C. Fungal biomass was quantified by widely acknowledged growth biomarker ergosterol. The extraction of the enzymatic complex was performed and laccase, Mn-dependent peroxidase (MnP), and lignin peroxidase (LiP) activities were determined. Furthermore, HCB and its metabolites were quantified by gas chromatography and chlorides by potentiometric titration. Results evidenced that HCB did not interfere in fungal growth, though the only detected enzymatic activity was laccase. MnP and Lip were not detected during D. castanella growth in soil. The peak of laccase enzymatic activity occurred in the presence of HCB. In addition, the laccase exhibited thermostability. Therefore, we hereby shed light on the role of laccase in the degradation of HCB by an efficient low-cost and environmentally safe detoxification mechanism.

Optimization and validation of a QuEChERS-based method for the simultaneous environmental monitoring of 218 pesticide residues in clay loam soil

A modified QuEChERS method was optimized, validated and verified for the extraction of 218 pesticide residues in agricultural soil samples. The 218 analytes are extracted using a single step, without clean-up, with matrix-matched calibration, and two complementary techniques: liquid and gas chromatography tandem triple quad mass spectrometry (LC-MS/MS and GC-MS/MS). Some of the parameters such as salts, acidity of the extraction solvent, sample moisture and some mechanical changes in the procedure were optimized to improve the overall performance for the target compounds and the soil matrix. The method was fully validated on a representative agricultural soil sample of the Canary Islands (clay loam soil) in terms of linearity, accuracy and precision. To avoid matrix effects, matrix-matched calibration curves (R² ≥ 0.99) were used for all target analytes. 100% of the compounds can be quantified with limits of quantification (LOQ) lower than the limit typically used in soils (50 ng g^-1), with 92% of compounds presenting a LOQ that is at least 10 times lower than that normally required. The limits of detection (LOD) ranged between 0.024 and 6.25 ng g^-1. The validated method was applied to a series of actual samples of agricultural soil (n = 18). In addition, as a further verification of its potential, the results of the application of the method in the investigation of clay loam soil samples that were obtained from underneath wildlife carcasses in the context of an environmental forensic investigation are also presented.

Determination of quaternary ammonium herbicides in soils. Comparison of digestion, shaking and microwave-assisted extractions

Very challenging analytical problems arise from the continuous introduction in agriculture of chemical pesticides. Particularly, diquat (DQ), paraquat (PQ) and difenzoquat (DF) are a difficult group of quaternary ammonium herbicides to analyze. This article reviews and addresses the most relevant analytical methods for determining the selected herbicides in soil. We discuss and critically evaluate procedures, such as digestion-based methods, shaking extraction and microwave-assisted extraction (MAE). Clean-up of extracts was performed by solid-phase extraction (SPE) using silica cartridges. Detection of these herbicides was carried out by liquid chromatography (LC) coupled to UV detection and mass spectrometry (MS) as confirmatory technique. Recoveries ranged from 98% to 100% by digestion, from no recovered to 61% by shaking, and from 102% to 109% by MAE with estimated quantification limits between 1.0 microg/kg and 2.0 microg/kg by digestion and 5.0 mug/kg and 7.5 microg/kg by MAE using LC/MS-MS as detection technique. The recoveries obtained under the optimum conditions are compared and discussed with those obtained from digestion extraction and MAE.

Response surface methodology for the microwave-assisted extraction of insecticides from soil samples

The extraction of two pyrethroid insecticides (deltamethrin and alpha-cypermethrin) together with three organophosphorus insecticides (dimethoate, diazinon and malathion) from soil samples was carried out with microwave-assisted technology. Experimental designs showed that extraction temperature, addition of water to the extractant and solvent/soil ratio were the variables that affected the recoveries of the pesticide the most. Response surface methodology was applied to find the optimum values of the variables involved in the extractions of the analytes. In addition, in order to achieve near-optimal extraction conditions, a desirability function was used to optimize the five pesticides simultaneously. The optimized conditions were applied to different types of soils.

ESTABELECIMENTO DE METODOLOGIAS DE EXTRAÇÃO DE HEXACLOROBENZENO (HCB) DE SEDIMENTO E ÁGUA DE ESTUÁRIO E DO MAR

RESUMO O hexaclorobenzeno (HCB) foi amplamente utilizado como fungicida e é também subproduto de vários processos industriais, como na fabricação de solventes. Suas características químicas o tornam pouco disponível à degradação química e biológica, levando a bio-acumulação e biomagnificação ao longo da cadeia alimentar. Assim, sua detecção e quantificação em organismos e no ambiente são importantes e, para isto, metodologias eficientes devem possibilitar o rastreamento e a quantificação de contaminação ambiental da maneira mais econômica. Este trabalho comparou diferentes métodos de extração de HCB de sedimentos e águas de estuário e de mar, avaliando as vantagens de cada método. Os testes de recuperação utilizaram amostras de sedimentos e águas de estuário e mar tratadas com HCB em mistura com 14C-HCB como radiotraçador e quantificação do radiocarbono por espectrometria de cintilação em líquido (ECL). A recuperação de 14C-HCB das águas foi comparada por extração das amostras com hexano em coluna C18 e extração líquido-líquido também com hexano como solvente. Nos sedimentos testouse extração com mistura de hexano:acetona e energia de microondas. A extração por fase sólida (C18) foi o melhor método de extração de água, com 88,3% e 83,4% de recuperação, respectivamente de água de estuário e de mar. A extração de sedimento por microondas recuperou 99,5% e 99,9% de radiocarbono, respectivamente de sedimentos de estuário e de mar. A análise custo/benefício indica a extração por coluna C18 para águas e a extração por microondas para sedimentos como os melhores métodos de recuperação e que possibilitarão boa detecção de HCB em estudos de poluição.

Applications of microwave-assisted processes (MAP™) to environmental analysis

The use of microwave-assisted extraction has gained wide acceptance as a powerful tool for the recovery of environmental contaminants and their subsequent analysis. This paper reviews the historical and fundamental basis of the technology. It also provides a cursory review of the current state-of-the-art and literature (2000-2006) in the area of environmental analysis in addition to providing a critical review of the level of efforts being devoted to its further development.

VOLATILIZAÇÃO E LIXIVIAÇÃO DE 14C-HEXACLOROBENZENO EM SOLO CONTAMINADO

RESUMO A possibilidade de contaminação do ar e da água a partir de solo contaminado com hexaclorobenzeno foi estudada em laboratório através da análise da volatilização e da lixiviação de 14C-hexaclorobenzeno neste solo. Para o estudo de volatilização, amostras de terra contaminada misturadas a fontes de matéria orgânica, cal, ou alagadas foram tratadas com solução de 14Chexaclorobenzeno; os 14C-compostos voláteis formados foram capturados por lâminas de poliuretano, extraídos com hexano e analisados por Espectrometria de Cintilação em Líquido. A lixiviação do hexaclorobenzeno foi estudada através de percolação de água em tubos de PVC contendo amostras de terra contaminada tratadas com bagaço de cana de açúcar e/ou cal e solução de 14C-hexaclorobenzeno, dispostas sobre amostras de terra não contaminada; os tubos foram seccionados e a terra e a água lixiviada foram analisadas por Espectrometria de Cintilação em Líquido. Houve formação de14C-compostos voláteis em todas as amostras de terra, principalmente nas amostras alagadas e com adição de matéria orgânica e não se observou lixiviação do 14Chexaclorobenzeno, indicando possibilidade de contaminação do ar, mas não de águas subterrâneas.

Influence of soil properties on bioaccumulation of 14C-simazine in earthworms Eisenia foetida

The toxicity of pesticides has been evaluated by several methods including tests with earthworms in both artificial and natural soils treated with the compounds. The ecological niches of earthworms make them good bioindicators of soil contamination. The bioaccumulation of 14C-simazine (6-chloro-N2-N4-diethyl- 1,3,5-triazine-2,4-diamine) was evaluated in earthworms (Eisenia foetida) maintained during three months in two substrates with different physical-chemical characteristics. The substrates were treated with 3.0 mg and 330 kBq of 14C-simazine kg(-1) substrate. Results indicated that worms did not influence simazine dissipation in both substrates as indicated by similar recoveries and with no statistical differences with and without earthworms. The radiocarbon recoveries were 86.8 and 95.3%, respectively in the substrates with lower and higher organic matter contents with earthworms, and 91.0 and 107.4% in the same substrates without worms. However, in earthworms the recoveries were statistically higher when they were maintained in the substrate with lower amount of organic matter (0.89%) than from the higher one (0.33%). Consequently, 14C-simazine bioconcentration factor (BCF) was also greater in the substrate with lower organic matter (6.89+/-1.55) than in the substrate with higher organic matter content (0.88+/-0.06). The results suggest that the higher soil organic matter content will cause lower probability of contamination of soil organisms with simazine.