Nitrate is an abundant ion that is present in many industrialized products and the environment. Various analytical methods have been described using the Griess-Ilosvay reagent for the determination of nitrate in different matrices after its reduction to nitrite, in most cases with metallic cadmium as the reducer. This work proposes a new method using aluminum spheres coated with a copper film for this reduction. To optimize the method, it was important to evaluate the conditions for the deposition of the copper film on the aluminum spheres, using a Doehlert matrix. The optimized method provided an analytical range from 2.0 to 100 µmol L-1, with a coefficient of determination of 0.9996 and a standard deviation of residuals (sres) of 7.59 x 10-4. The Limits of Detection and Quantification were 0.59 and 2.0 µmol L-1 respectively. The method was applied using mineral water samples and was shown to provide repeatability less than 6.98% and accuracy obtained through recovery essays between 81.1 and 104.6% for the determination of nitrate in this type of sample.
The objective of this study was to optimize and validate a solid-liquid extraction method with low-temperature partitioning (SLE/LTP) for the analysis of pesticides. This method was coupled with gas chromatography (GC/ECD) and used to evaluate the degradation of bifenthrin and pirimiphos-methyl in maize grains on exposure to ozone. The optimized SLE/LTP-GC/ECD method is simple, effective and consumes low quantities of the solvent. It can be routinely used for the determination of bifenthrin and pirimiphos-methyl in maize samples. The use of this method of analysis determined that the levels of the insecticides in maize grains were reduced on exposure of the grains to the ozone gas. The observed reduction in the levels of insecticide was directly proportional to the increase in the concentration of the ozone gas.
Difenoconazole residues in strawberry fruit cultivated in pots were estimated using the solid-liquid extraction with low temperature partition (SLE/LTP) method for sample preparation and gas chromatography with electron capture detection (GC/ECD) for analysis. The optimized method presented excellent recovery values from fortified samples and reproducibility (average recovery values ≥ 98%; CV values < 15%). Linearity of response was demonstrated (r = 0.995) with a detection limit of 9 µg kg-1. The method was successfully applied for the determination of difenoconazole residues in strawberries. Based on these results, the fungicide dissipates quickly, but the residual concentration increases after multiple applications.
The distribution and dissipation of herbicides on soils are dynamic and unique processes for each soil-herbicide relation. In this research, the half-life of diuron was determined in five soils (Red-Yellow Latosol, Red Latosol, and Yellow Latosol), with different pH values. Diuron concentrations were determined in samples of each soil collected at eight different times (1, 8, 15, 22, 36, 66, 96 and 156 days after herbicide application at 3.0kg ha-1). Part of each soil sample was used to quantify diuron by high performance liquid chromatography. The other part of soil sample was used to do biological tests in order to confirm the results of chromatographic analysis. It was found that the persistence of diuron is dependent on the physical and chemical soil attributes. However, the correction of soil pH favored only herbicide degradation in sandy soils with low organic matter content. The half-life of diuron in soils ranged from 40 to 91 after its application and it was higher in soil with higher organic matter content. The biological tests confirmed these results and they were efficient and complementary to the chromatographic analysis.
A distribuição e a dissipação dos herbicidas nos solos são processos dinâmicos e únicos para cada relação solo-herbicida. Neste trabalho, a meia-vida do diuron foi determinada em cinco solos (Latossolo Vermelho Amarelo, Latossolo Vermelho e Latossolo Amarelo), com diferentes valores de pH. As concentrações do diuron foram determinadas em amostras dos referidos solos coletadas em oito épocas (1, 8, 15, 22, 36, 66, 96 e 156 dias após a aplicação do herbicida na dose 3,0kg ha-1). Em uma parte dessas amostras, foi feita a quantificação do diuron por cromatografia líquida de alta eficiência e, na outra parte, os testes biológicos, visando à confirmação dos resultados das análises cromatográficas. Constatou-se que a persistência do diuron é dependente dos atributos físicos e químicos dos solos. Todavia, a correção do pH do solo favoreceu apenas a degradação do herbicida em solos arenosos com baixo teor de matéria orgânica. A meia-vida do diuron nos solos estudados variou de 40 a 91 após a sua aplicação, sendo maior no solo com maior teor de matéria orgânica. Esses resultados foram confirmados pelos testes biológicos que se mostraram eficientes e complementares às análises cromatográficas.
Components in complex matrices can cause variations in chromatographic response during analysis of pesticides by gas chromatography. These variations are related to the competition between analytes and matrix components for adsorption sites in the chromatographic system. The capacity of the pesticides chlorpyrifos and deltamethrin to be adsorbed in the injector and chromatographic column was evaluated by constructing three isotherms and changing the column heating rate to 10 and 30 ºC min-1. By using ANCOVA to compare the slope of calibration graphs, results showed that the higher the injector temperature (310 ºC) the lower the pesticide adsorption. Also, deltamethrin influenced the adsorption of chlorpyrifos on the column chromatographic.
A preliminary analyses of the possible contamination of surface and groundwater by the active ingredients of the pesticide products used in the areas with intensive agricultural activities of Alto Paranaíba region, MG, Brazil, was carried out. The active ingredients and formulated products most used in the region were identified and their characteristics of environmental importance were presented. The EPA screening criteria, the groundwater ubiquity score (GUS) and the criteria proposed by Goss were used to evaluate which pesticides might contaminate the local waters. Among the active ingredients studied, several present risks to the local aquatic environment.
The objective of this study was to evaluate the use of the matrix solid-phase dispersion technique associated with purification at low temperature for the determination of pyrethroids in butter. Evaluated parameters included: sample/adsorbent ratio, type of adsorbent and extractor solvent. The optimized method was validated based on predetermined requirements. The detection limits of the pyrethroids cypermethrin and deltamethrin were 0.082 and 0.11 μg g-1, and quantification limit were 0.28 and 0.32 μg g-1, respectively, with extraction percentages near 90% and coefficients of variation less than of 10%..
The feasibility of using constructed wetlands (CWs) for the mitigation of pesticide runoff has been studied in the last decade. However, a lack of related data was verified when subsurface flow constructed wetlands (SSF CWs) are considered for this purpose. In the present work, SSF CWs were submitted to continuous ametryn addition and evaluated during an 11-week period, with the aim of determining the feasibility of these systems for mitigation of contaminated water. Ametryn was not added to one CW cell in order to provide a control for the experiments. Monitoring of treatment performance was executed by standard water quality parameters, ametryn chromatography quantification and macrophyte (Typha latifolia L.) nutritional and agronomic property analysis. Results indicated that 39% of the total initially added amount of ametryn was removed, transferred or transformed. Herbicide metabolism and mineralisation were carried out by chemical and biological mechanisms. No statistic differences were observed in nutritional contents found in the T. latifolia crops of the CWs after the experimental period. Moreover, the biomass production (one valuable source of renewable energy) was equal to 3.3 t·ha-1 (dry matter) in wetland cells. It was concluded that constructed wetland systems are capable of mitigating water contaminated with ametryn, acting as buffer filters between the emission sources and the downstream superficial water bodies.
OBJECTIVE:To determine if lipid sources with different unsaturated to saturated fatty acid ratios, (PUFA+MUFA)/SFA in the diet alter the lipid profile of tissues, the lipid concentration (mg/g) of the hepatic and mesenteric tissues and the lipid digestibility. METHODS:Gas chromatography was used to determine the profile of fatty acids in the hepatic and adipose tissues of rats fed with different lipid sources. The digestibility coefficient was determined based on the ratio between lipid intake and excreted in the feces. RESULTS:Different lipid sources (soy oil, butter, margarine and pig and fish fat) did not alter the digestibility coefficient and the hepatic weight, but they altered the lipid deposition in all adipose tissue evaluated. No direct correlation was observed between dietary non-essential fatty acid profile and its deposition in the studied adipose tissues, because of de novo which impedes the identification of the dietary fatty acid. CONCLUSION:A direct relationship was not verified between the dietary fatty acid profile and its deposition in the studied adipose tissues, except for the trans and linoleic (C18:2) fatty acids which are not synthesized in the rat. The tissue concentration of these fatty acids was directly proportional to their dietary sources. The (PUFA+MUFA)/SFA ratio found in the hepatic tissue of the different groups, was directly proportional to the values presented in the dietary lipid sources. However, this association was not observed in the adipose tissue.
OBJETIVO:Determinar se fontes lipídicas com diferentes razões de ácidos graxos insaturados e saturados (PUFA+MUFA)/SFA na dieta altera o perfil lipídico tecidual, a concentração de lipídios (mg/g) dos tecidos hepáticos e mesentérico e a digestibilidade lipídica. MÉTODOS: Foi realizada cromatografia gasosa para determinar o perfil de ácidos graxos nos tecidos hepático e adiposo de ratos alimentados com diferentes fontes lipídicas. O coeficiente de digestibilidade foi determinado a partir da relação entre a quantidade de lipídios consumidos e a quantidade fecal excretada. RESULTADOS:Diferentes fontes lipídicas (óleo de soja, manteiga, margarina e gorduras de porco e de peixe) não alteraram o coeficiente de digestibilidade e o peso hepático, mas alteraram a deposição de lipídios em todos os tecidos adiposos estudados. Não foi possível fazer a correlação direta entre o perfil dietário dos ácidos graxos não essenciais e sua deposição nos tecidos estudados, visto que a lipogênese de novo impede a identificação dos ácidos graxos dietários. CONCLUSÃO:Não foi constatada uma relação direta entre o perfil dietário dos ácidos graxos e sua deposição nos tecidos estudados, exceto para os ácidos graxos trans e linoléico (C18:2) que não são sintetizados no rato. Esses ácidos graxos apresentaram uma concentração tecidual diretamente proporcional àquela das fontes dietárias. Quanto à razão (PUFA+MUFA)/SFA, encontrada no tecido hepático dos diferentes grupos, observa-se que esta foi diretamente proporcional aos valores apresentados pelas fontes lipídicas dietárias. Entretanto, essa associação não foi observada nos tecidos adiposos analisados.
The liquid-liquid extraction with the low temperature partition technique was developed for the analysis of four pyrethroids in water by CG. Using a factorial design the extraction technique was optimised evaluating the effect of the variables ionic strength, contact time and proportion between sample and solvent volumes. The validation parameters sensitivity, precision, accuracy and detection and quantification limits were evaluated. The LOD and LOQ of the method varied from 1.1 to 3.2 µg L-1 and 2.7 to 9.5 µg L-1, respectively.
The adsorption of triadimenol (1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol) on soil samples with varying contents of organic matter was studied. The adsorption was described by means of the Freundlich's isoterm. An increase in the capacity of adsorption was observed as the content of organic carbon in the matrix increased. That effect was observed when removing the organic matter from the soil, when adding a urban waste compost to the soil sample as well as to the soil sample without organic matter, and also after leaving proportions of urban waste compost incubated in these matrices for a period of 120 days. The results show that the adsorption of the triadimenol in the soil is dependent of its content of organic carbon.
In this work the contamination, by organochlorinated, of a drinking water source located in the region of Viçosa, MG, was evaluated. The identification and quantification of the analytes was carried out using a gas-chromatograph equipped with an electron capture detector after liquid-liquid extraction and concentration. Four insecticides, Aldrin, Epoxy heptachloride, Endrin and op'- DDT were detected in concentrations that are higher than the safety limits established in the Brazilian legislation.