Determining Mancozeb Deposition Benchmark Values on Apple Leaves for the Management of Venturia inaequalis.

Apple scab, caused by Venturia inaequalis, is the most common fruit and foliar disease in commercial apple production worldwide. Early in the production season, preventative contact fungicide sprays are essential for protecting highly susceptible continuously unfolding and expanding young leaves. In South Africa, mancozeb is a key contact fungicide used for controlling apple scab early in the season. The current study developed deposition benchmarks indicative of the biological efficacy of mancozeb against apple scab, using a laboratory-based apple seedling model system. The model system employed a yellow fluorescent pigment that is known to be an effective tracer of mancozeb deposition. A concentration range of mancozeb (0.15 to 1 times the registered dosage) and fluorescent pigment concentrations was sprayed onto seedling leaves, which yielded various fluorescent particle coverage (FPC%) levels. Modeling of the FPC% values versus percent disease control yielded different benchmark values when disease quantification was conducted using two different methods. Thermal infrared imaging (TIRI) disease quantification resulted in a benchmark model where 0.40%, 0.79%, and 1.35 FPC% yielded 50, 75, and 90% apple scab control, respectively. These FPC% values were higher than the benchmarks (0.10, 0.20, and 0.34 FPC%, respectively) obtained with quantitative real-time PCR (qPCR) disease quantification. The qPCR benchmark model is recommended as a guideline for evaluating the efficacy of mancozeb sprays on leaves in apple orchards since the TIRI benchmark model underestimated disease control. The TIRI benchmark model yielded 68% disease control at the lowest mancozeb dosage, yet no visible lesion developed at this dosage. Both benchmark models showed that mancozeb yielded high levels of disease control at very low concentrations; for the qPCR benchmark model the FPC% value of the FPC90 (90% control) corresponded to 0.15 times that of the registered mancozeb concentration in South Africa, i.e., 85% lower than the registered dosage.

Amphiphilic polymer based nanoformulations of mancozeb for management of early blight in tomato.

Controlled release (CR) nanoformulations of Mancozeb (Manganese-zinc double salt of N, N-bisdithiocarbamic acid), a protective fungicide, have been developed using poly (ethylene glycols) (PEGs) based functionalized amphiphilic copolymers and evaluated for the management of early blight in tomato. During the field experiment, it was observed that number of infected leaflets/plants were less in developed formulation treated plants as compared to commercial products. Number of infected leaflets per plant was 2.40-4.60 and the number of fruits per plant were 6.40-9.00 at 50 mg L-1, whereas at 100 mg L-1, the corresponding numbers were 2.10-4.10 and 6.30-9.10 respectively. These formulations can be used to optimize the release of Mancozeb to achieve disease control for the desired period depending upon the matrix of the polymer used. Importantly, sufficient amount of active ingredient remains available for a reasonable period of time after application leading to reduced number of applications of pesticide.

Evaluation of cytotoxicity, genotoxicity and ecotoxicity of nanoemulsions containing Mancozeb and Eugenol.

Mancozeb is a fungicide widely used in agriculture, mostly against the pathogen Glomerella cingulata responsible for the rot of ripe grape, but presents high toxicity. Strategies are sought to reduce the toxicity of this fungicide and alternative treatments are welcome. An alternative could be the use of clove oil, which has Eugenol as its major compound, and has antifungal potential against G. cingulata, however, Eugenol is susceptible to degradation processes which may compromise its efficacy. The nanoencapsulation of Mancozeb and Eugenol is a possible strategy to overcome the limitations of toxicity, solubility and instability of these compounds. Therefore, the objective of this study is to develop nanoemulsions containing Mancozeb (0.1 mg/mL) and Eugenol (33 mg/mL), isolated or associated, and evaluate the safety of these formulations through cytotoxicity, genotoxicity and ecotoxicity tests. Nanoemulsions were developed by the spontaneous emulsification method, cytotoxicity and genotoxicity were evaluated in healthy human cells through MTT, Dichlorofluorescein diacetate and Picogreen tests, and ecotoxicity assessment was carried out using the chronic toxicity test in springtails. After preparation, the physicochemical characterization of the nanoemulsions were performed which presented mean particle size between 200 and 300 nm, polydispersity index less than 0.3, negative zeta potential and acid pH. The nanoencapsulation was able to avoid the reduction of the cell viability caused by Mancozeb, while Eugenol was shown to be safe for cell use in both free and nanostructured forms, however the association of the two active compounds showed toxicity in the higher doses of Mancozeb. In the ecotoxicity tests, both free Mancozeb and Eugenol forms presented high toxic potential for soil, whereas the nanoencapsulation of these compounds did not cause a reduction in number of springtails. Therefore, from the tests performed, it was possible to observe that nanoencapsulation of Mancozeb and Eugenol is a safe alternative for the application of these compounds mainly in agriculture.

Effects of hydrochemistry variables on the half-life of mancozeb and on the hazard index associated to the sum of mancozeb and ethylenethiourea.

Mancozeb is a dithiocarbamate non-systemic agricultural fungicide with multi-site, protective action. It helps to control many fungal diseases in a wide range of field crops, fruits, nuts, vegetables, and ornamental plants. We have investigated the stability profiles of mancozeb in aqueous solutions to determine the effect of pH, temperature and light on the degradation process of mancozeb. In addition, the toxicological risk for humans associated with the joint intake of mancoze7b and its final degradation product, ethylenethiourea (ETU), was calculated and modelled as a function of the experimental conditions. Stability study results showed a very low stability profile of mancozeb in all the aqueous solutions with rapid degradation that varied with experimental conditions. The process followed first order kinetics. The study of the degradation kinetics showed a significant effect of pH*temperature interaction on the degradation process. The results also expressed that light has a greater impact on the stability of mancozeb and the formation of ETU. The current study concludes that mancozeb is unstable in aqueous solutions, particularly at an acid pH, in addition to presenting both severe light and lower temperature sensitivity. The toxicological risk associated with mancozeb degradation increases with time and temperature, being higher at basic pH and in absence of light.

Aquatic environmental safety assessment and inhibition mechanism of chemicals for targeting Microcystis aeruginosa.

Cyanobacteria are a diverse group of Gram-negative bacteria that produce an array of secondary compounds with selective bioactivity against vertebrates, invertebrates, fungi, bacteria and cell lines. Recently the main methods of controlling cyanobacteria are using chemicals, medicinal plants and microorganism but fewer involved the safety research in hydrophytic ecosystems. In search of an environmentally safe compound, 53 chemicals were screened against the developed heavy cyanobacteria bloom Microcystis aeruginosa using coexistence culture system assay. The results of the coexistence assay showed that 9 chemicals inhibited M. aeruginosa effectively at 20 mg L(-1) after 7 days of exposure. Among them dimethomorph, propineb, and paraquat were identified that they are safe for Chlorella vulgaris, Scenedesmus obliquus, Carassius auratus (Goldfish) and Bacillus subtilis within half maximal effective concentration (EC50) values 5.2, 4.2 and 0.06 mg L(-1) after 7 days, respectively. Paraquat as the positive control observed to be more efficient than the other compounds with the inhibitory rate (IR) of 92% at 0.5 mg L(-1). For the potential inhibition mechanism, the chemicals could destroy the cell ultrastructure in different speed. The safety assay proved dimethomorph, propineb and paraquat as harmless formulations or products having potential value in M. aeruginosa controlling, with the advantage of its cell morphology degrading ability.

Kinetic and thermodynamic investigation of mancozeb degradation in tomato homogenate during thermal processing.

BACKGROUND: The kinetic and thermodynamic parameters of mancozeb degradation in tomato homogenates under the conditions prevailing in the manufacture of tomato products (at 60-100 °C for 0-60 min) were investigated. A gas chromatography-mass spectrometry method was used to analyse residual mancozeb in tomato homogenate. Ethylenethiourea (ETU), the main toxic degradation product of mancozeb, was measured by high-performance liquid chromatography (HPLC)-with photodiode array detector (PDA). RESULTS: The degradation of mancozeb and the formation of ETU in tomato homogenates were adequately described as first-order kinetics. Dependence of the rate constant followed the Arrhenius relationship. Apparent activation energies, temperature coefficients, half time and time to reduce to 90% of the initial value of mancozeb were calculated as kinetic parameters. The thermodynamic parameters of mancozeb were also described as Δg(d) = - 2.440 and 7.074 kJ mol⁻¹; Δh(d) = - 32.555 and - 42.767 kJ mol⁻¹; Δs(d) = - 0.090 and - 0.150 kJ mol⁻¹ K⁻¹; K(e) = 0.414 and 9.797 L g⁻¹ for 333 and 373 K respectively. CONCLUSION: Current findings may shed light on the reduction of mancozeb residue and its toxic degradation product during thermal processing of tomatoes and may also be valuable in awareness and prevention of potential risks from dietary exposure.

The effects of pesticide mixtures on degradation of pendimethalin in soils.

Most agronomic situations involve a sequence of herbicide, fungicide, and insecticide application. On the other hand, use of pesticidal combinations has become a standard practice in the production of many agricultural crops. One of the most important processes influencing the behavior of a pesticide in the environment is its degradation in soil. It is known that due to several pesticide applications in one vegetation season, the pesticide may be present in mixtures with other pesticides or xenobiotics in soil. This study examines the role which a mixture of chemicals plays in pesticide degradation. The influence of other pesticides on the rate of pendimethalin (PDM) degradation in soil was measured in controlled conditions. Mixtures of PDM with mancozeb or mancozeb and thiamethoxam significantly influenced the degradation of pendimethalin under controlled conditions. The second type of mixtures, with metribuzin or thiamethoxam, did not affect the behavior of pendimethalin in soil. Also, we determined the influence of water content on the rate of pendimethalin degradation alone in two soils and compared it to the rate in three pesticide mixtures. We compared two equations to evaluate the predictors of the rate of herbicide dissipation in soil: the first-order kinetic and the non-linear empirical models. We used the non-linear empirical model assuming that the degradation rate of a herbicide in soil is proportional to the difference of the observed concentration of herbicide in soil at time and concentration of herbicide in the last day of measurement.

Residue dynamics of fenamidone and mancozeb on gherkin under two agro climatic zones in the state of Karnataka, India.

Residue dynamics of fenamidone and mancozeb on gherkin was evaluated at two different agro climatic zones i.e. at Bangalore (Zone-1) and Dharwad (Zone-2) in the state of Karnataka, India. Two treatments of the combination formulation (fenamidone 10% + mancozeb 50%) were given at the standard dose 150 + 750 g a.i. ha(-1) and double dose 300 + 1,500 g a.i. ha(-1). Initial residue deposits of fenamidone were 0.467 and 0.474 mg kg(-1) at Zone-1 and 2, respectively from standard dose treatment. From double dose treatment they were 0.964 and 0.856 mg kg(-1), respectively. Fenamidone residues persisted for 15 and 10 days and dissipated with the half-life of 4 and 3 days at Zone-1 and 2, respectively. Mancozeb residue deposits on gherkin were 0.383 and 0.428 mg kg(-1) from standard dose and 0.727 and 0.626 mg kg(-1) from double dose treatment at Zone-1 and 2, respectively. Mancozeb residues dissipated with the half-life of 2 and 1 day, respectively. Residues of both fenamidone and mancozeb dissipated faster at Zone-2 compared to Zone-1. The limit of quantification of fenamidone and mancozeb were 0.02 and 0.1 mg kg(-1), respectively in both gherkin and soil. Residues of fenamidone and mancozeb in soil collected on the 20th day from the 2 locations were found to be below quantifiable limit of both fungicides.

Electrochemical quantification of mancozeb through tungsten oxide/reduced graphene oxide nanocomposite: A potential method for environmental remediation.

The extensive use of pesticides for better yield of crops have become major human concern over the decades. Pesticides are widely used in the fields to kill weeds and pests on the vegetable and crops to improve the quality and yield of the food knowing the fact that pesticides residue in food are very lethal for human being. Amongst, the hazardous pesticides, mancozeb is widely applied in the protection of crops. Thus the quantification of mancozeb residue is of great importance. This study reports the electrochemical monitoring of mancozeb through tungsten oxide reduced graphene oxide (WO3/rGO) nanocomposite. The engineered nanocomposite was characterized though different analytical tools such as FTIR, XRD and TEM to examine crystallinity, internal texture and the size. The FTIR result confirm the functionalities of GO and WO3/rGO nanocomposite in finger print and functional group region. Through XRD analysis, the size of the WO3/rGO nanocomposite was calculated as 31.6 nm. While the TEM analysis was also exploited to examine the 2D texture of GO and nanometric size of the WO3/rGO. To ensure the conductive nature of the WO3/rGO nanocomposite, the glassy carbon electrode was modified and exploited for cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the modified sensor showed exceptional response for mancozeb. The linear dynamic range was set from 0.05 to 70 µM in BRB buffer of pH 4. The LOD and LOQ for proposed method was calculated as 0.0038 and 0.0115 µM. The analytical applicability of chemically modified sensor was investigated in real matrix of different vegetable samples and the recovery values were observed in acceptable range. The electrochemical examination of present work reveals that WO3/rGO nanocomposite can be an exceptional aspirant for the determination of mancozeb at commercial level.

Surface-Enhanced Raman Spectroscopy (SERS) of Mancozeb and Thiamethoxam Assisted by Gold and Silver Nanostructures Produced by Laser Techniques on Paper.

Advanced gold (Au) and silver (Ag) nanostructures were produced by laser techniques on printer paper substrate. Surface-enhanced Raman spectroscopy (SERS) analyses of the fungicide mancozeb (Dithane DG) and insecticide thiamethoxam (Aktara 25 BG) in quantities smaller than usually applied in agricultural medicine were performed for the first time assisted by the structures fabricated. The investigations and results show an easy alternative and cheap way to detect small amounts or residue of harmful environmental pollutants, which has a direct bearing on food quality and thus on human health.

A study of some sorbents for adsorption of mancozeb residue from soil of tobacco fields of Mazandaran, Iran by analytical methods.

The purpose of this study is to accesses the efficiency of removal of pesticide Mancozeb (Dithiocarbamates family) using different sorbents (synthetic zeolite type A, Humic Acid (HA) extracted from soil of Noshahr jungle in the north of Iran and mixture of them). The adsorption efficiency of the adsorbents was evaluated by Freundlich isotherms to select the best sorbent. The main effective parameters such as the amount of sorbents, pH, agitating time and concentrations of Mancozeb were tested. The results for 1.6 ppm of pesticide at pH=5 shows the optimum values 2, 0.75, 0.5 g for HA, zeolite NaA and mixture of them, respectively. The adsorption capacity decreases as pH increases and the adsorption effect for 0.1 g of sorbents at pH=5 were obtained in the order: (mixture of sorbents) > (synthetic zeolite type A) > (extracted Humic Acid).

Comparative study of antifungal effect of green and chemically synthesised silver nanoparticles in combination with carbendazim, mancozeb, and thiram.

This study reports synthesis and characterisation of silver nanoparticles and their effect on antifungal efficacy of common agricultural fungicides. Silver nanoparticles were synthesised using biological and chemical reduction methods employing Elettaria cardamomum leaf extract and sodium citrate, respectively. Nanoparticles were then characterised using UV-Visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy, and dynamic light scattering (DLS). While XRD assigned particles size of 31.86 nm for green and 41.91 nm for chemical silver nanoparticles with the help of the Debye-Scherrer formula, DLS specified monodisperse nature of both suspensions. Nanoparticles were tested individually and in combination with fungicides (carbendazim, mancozeb, and thiram) against fungal phytopathogens. Silver nanoparticles exhibited good antifungal activity and minimum inhibitory concentration (MIC) was observed in the range of 8-64 µg/ml. Also, they positively influenced the efficacy of fungicides. The mean MIC value (mean ± SD) for combination of all three fungicides with green AgNPs was 1.37 ± 0.6 µg/ml and for chemical AgNPs was 1.73 ± 1.0 µg/ml. Hence, it could be concluded that green AgNPs performed better than chemical AgNPs. Synergy was observed between green AgNPs and fungicides against Fusarium oxysporum. In conclusion, this study reports synthesis of monodisperse silver nanoparticles which serve as efficient antifungal agents and also enhance the fungicidal action of reported agricultural fungicides in combination studies.

Reactive oxygen species generation by the ethylene-bis-dithiocarbamate (EBDC) fungicide mancozeb and its contribution to neuronal toxicity in mesencephalic cells.

Previous in vitro studies in our laboratory have shown that mancozeb (MZ) and maneb (MB), both widely used EBDC fungicides, are equipotent neurotoxicants that produce cell loss in mesencephalic dopaminergic and GABAergic cells after an acute 24h exposure. Mitochondrial uncoupling and inhibition were associated with fungicide exposure. Inhibition of mitochondrial respiration is known to increase free radical production. Here the mechanism(s) of neuronal damage associated with MZ exposure was further explored by determining the role that reactive oxygen species (ROS) played in toxicity. Damage to mesencephalic dopamine and GABA cell populations were significantly attenuated when carried out in the presence of ascorbate or SOD, indicative of a free radical-mediated contribution to toxicity. ROS generation monitored by hydrogen peroxide (H(2)O(2)) production using Amplex Red increased in a dose-dependent manner in response to MZ. Inhibition of intracellular catalase with aminotriazole had little effect on H(2)O(2) generation, whereas exogenously added catalase significantly reduced H(2)O(2) production, demonstrating a large extracellular contribution to ROS generation. Conversely, cells preloaded with the ROS indicator dye DCF showed significant MZ-induced ROS production, demonstrating an increase in intracellular ROS. Both the organic backbone of MZ as well as its associated Mn ion, but not Zn ion, were responsible and required for H(2)O(2) generation. The functionally diverse NADPH oxidase inhibitors, diphenylene iodonium chloride, apocynin, and 4-(2-aminoethyl)benzene-sulfonyl fluoride hydrochloride significantly attenuated H(2)O(2) production by MZ. In growth medium lacking cells, MZ produced little H(2)O(2), but enhanced H(2)O(2) generation when added with xanthine plus xanthine oxidase whereas, in cultured cells, allopurinol partially attenuated H(2)O(2) production by MZ. Minocycline, an inhibitor of microglial activation, modestly reduced H(2)O(2) formation in mesencephalic cells. In contrast, neuronal-enriched cultures or cultures treated with MAC-1-SAP to kill microglia, did not show an attenuation of ROS production. These findings demonstrate that Mn-containing EBDC fungicides such as MZ and MB can produce robust ROS generation that likely occurs via redox cycling with extracellular and intracellular oxidases. The findings further show that microglia may contribute to but are not required for ROS production by MZ.

Determination of dithiocarbamate fungicide propineb and its main metabolite propylenethiourea in airborne samples.

A simple, rapid and sensitive GC-MS method for the determination of dithiocarbamate fungicide propineb [polymeric zinc propylenebis (dithiocarbamate)] and an improved HPLC procedure for the simultaneous determination of its main metabolite, propylenethiourea, and ethylenethiourea, the main metabolite of all ethylenedithiocarbamates, in airborne samples are described. The method for the analysis of propineb involves the evolution of carbon disulfide (CS(2)), under acidic conditions in the presence of stannous chloride, extraction of the generated CS(2) into a layer of isooctane which is then analyzed for CS(2) content by GC-MS in SIM mode. Under the optimum conditions, the retention time of CS(2) was 1.89 min and the total time of chromatographic analysis was 5 min. Recoveries from spiking glass microfibre filters (GF/A) and silica gel filters were 86+/-7 (n=9) and 89+/-4 (n=9), respectively. The limit of detection is 0.7 ng per filter, which is equivalent to about 0.8-1.0 ng m(-3) in air. In parallel, an HPLC method with ultraviolet detection is presented for the simultaneous analysis of the metabolites. Separation of the two metabolites was attained in less than 5 min. Recoveries from spiking GF/A and silica gel filters for ethylenethiourea were 100+/-1 (n=3) and 98+/-2 (n=3), respectively, while for propylenethiourea were 102+/-1 (n=3) and 98+/-1 (n=3), respectively. The detection limits are about 36-43 and 40-49 ng m(-3) in air for ethylenethiourea and propylenethiourea, respectively. All the analytes spiked in the filters are proven to be stable for more than one month, at -4 degrees C.

Spectroscopic evaluation of the interaction between pesticides and chickpea cystatin: comparative binding and toxicity analyses.

The binding study of pesticides with proteins is of great importance in ecotoxicology. In this study, a comparative interaction mechanism of phytocystatin with three pesticides has been presented, each from a different class-glyphosate herbicide (GPS), chlorpyrifos insecticide (CPF), and mancozeb fungicide (MCZ). The interaction of purified chickpea cystatin (CPC) has been characterized by fluorescence, UV, and circular dichroism (CD) spectroscopic methods. The study revealed association constants (Ka) of 52 M(-1), 1.145 × 10(3) M(-1), and 36.12 M(-1) for the interaction of CPF, MCZ, and GPS with CPC, respectively, signifying the high affinity interaction for MCZ. Structural changes (at tertiary and secondary levels) were confirmed by UV-visible, intrinsic fluorescence and CD spectroscopy. The results showed that the effect on the CPC structure was more pronounced in the case of MCZ, which was followed by CPF and then GPS. The functional analysis of the pesticide treated inhibitor showed a decline in antipapain activity which varied with the time and dose as well as the class of pesticide. MCZ was relatively much more toxic as compared to CPF and GPS. Reactive oxygen species responsible for inhibitor damage were also analyzed. The results obtained implicate that the exposure of plants to pesticides may lead to physicochemical changes in proteins such as phytocystatins leading to physiological damage to the plant system.

Determination of degradation products and pathways of mancozeb and ethylenethiourea (ETU) in solutions due to ozone and chlorine dioxide treatments.

The objective of the present study was to determine the degradation products of mancozeb and ethylenethiourea (ETU) and elucidate the possible degradation pathways in solution as a result of chemical oxidation using ozone and chlorine dioxide. This study was developed in a solution at 100 ppm of mancozeb and ETU concentration over the course of 60 min. Two different oxidizing agents used in this study were (1) ozone at 3 ppm and (2) chlorine dioxide at 20 ppm. Ozone was continuously provided throughout the course of the reaction. Degradation products were detected with high-resolution GC-MS. The total analysis time was 4 min per sample combined with rapid GC separation and time-of-flight mass spectrometry (TOFMS). Hydrolysis of mancozeb led to m/z 144 ion fragmentation, which is 5-imidazoledithiocarboxylic acid, as a major degradation product. ETU showed M(+) 102, which corresponds to its mass, indicating this compound was stable in distilled water and did not undergo hydrolysis during 60 min. The average retention times of mancozeb and ETU were approximately 181-189 and 210-230 s, respectively. Ozonation of mancozeb produced ETU as a major product. Treatment of ETU with ozone produced several degradation compounds. From prolonged ozonation, the CS(2) or CS group was removed. Overall, several byproducts identified were M(+) 60, M(+) 84, M(+) 163, M(+) 117, and M(+) 267 by ozone and M(+) 117, M(+) 86, and M(+) 163 by chlorine dioxide treatment. Several of these have been reported, but others have never been reported previously.

Ozone and hydrogen peroxyacetic acid treatment to reduce or remove EBDCs and ETU residues in a solution.

Laboratory studies were conducted in a model system to determine the effects of ozone (1 and 3 ppm) and hydrogen peroxyacetic acid (HPA) (5 and 50 ppm) at pH 4.6, 7.0, and 10.7 and at 10 and 21 degrees C on the degradation of mancozeb in solution over a 30 min period. All samples were analyzed for residues by GLC and HPLC. Ozonation and HPA treatment were effective in degrading mancozeb in solution. Rate of mancozeb degradation was dependent on pH, with the fastest rate at pH 7.0. Ethylenethiourea (ETU) residue concentrations in the mancozeb solutions were monitored over 60 min. Under controlled conditions, the ETU residue concentrations increased during the 15 min reaction time and then decreased for all three pH values. At 3 ppm of ozone treatment, no ETU residues were detected at all three pH ranges after 15 min of reaction time. Degradation of ETU by HPA was greatest at pH 4.6, and no ETU residues remained after 5 min at either 5 or 50 ppm. The results showed that ozone and HPA gave excellent degradation of pesticide residues depending on pH and temperature. These experiments indicated the potential for the removal of pesticide residues on fruit and in processed products.

Chlorine and chlorine dioxide treatment to reduce or remove EBDCs and ETU residues in a solution.

Calcium hypochlorite (Ca(OCl)(2)) and chlorine dioxide (ClO(2)), common disinfecting and bleaching chemicals used in the food industry, are potent oxidizing agents. In this paper, the degradation effects of chlorine dioxide on mancozeb and ethylenethiourea (ETU) residues were investigated in a model system and compared with those of liquid chlorine, under various conditions such as differing concentration, pH, reaction time, and temperature. All samples were analyzed for residues by GLC and HPLC. Rate of mancozeb degradation was dependent on pH, with pH 4.6 being the most effective. Mancozeb residues decreased 40-100% with chlorine and chlorine dioxide treatments. ETU residue concentrations in mancozeb solutions were monitored over 60 min. Under controlled conditions, the ETU residue concentrations increased up to 15 min reaction time and then decreased in all three pH ranges. Treatment with both chlorine and chlorine dioxide at pH 4.6, yielded no ETU residues at both 10 and 21 degrees C. The results show that chlorine dioxide gives excellent degradation effects at lower concentrations than liquid chlorine.

Identification and quantitation by high-performance liquid chromatography of mancozeb following derivatization by 1,2-benzenedithiol.

Ethylenebisdithiocarbamate (EBDC) fungicides are the most important class of organic fungicides and exhibit a high degree of carcinogenicity, mutagenicity, and neurotoxicity. For that reason, the safe application of these fungicides in practice requires a convenient method for their determination, applicable to biological fluids. We describe a high-performance liquid chromatography (HPLC) assay. After elimination of the metal which defines the product (maneb, mancozeb, zineb.) with EDTA, the resulting EBDC is derivatized with 1,2-benzenedithiol to yield a cyclocondensation product, 1,3-benzodithiole-2-thione, which can then be quantitated by reversed-phase HPLC at 365 nm using a microBondapak C18 column. The mobile phase was methanol/H2O (70:30, v/v). The assay was linear from 0.25 to 100 microg/mL. Within- and between-day precision and accuracy for this assay were better than 9% and 6%, respectively. The lower limits of detection and quantitation were estimated to be 0.1 and 0.25 microg/mL, respectively. This simple new method has been applied to determine mancozeb concentration in rat urine samples from urinary excretion studies.

Solid-state UV-MALDI-MS assay of transition metal dithiocarbamate fungicides.

The determination of transition metal containing dithiocarbamate fungicides represents a challenging aspect of analytical object. They have a low stability, low solubility and stabilize versatile coordination monomers, dimers, disulfides and/or S-oxidized derivatives. Their diverse biological activities and agricultural implementation encompass plant prevention and crop protection against a variety of plants containing fungi and diseases of 400 pathogens and 70 cultures. Nonetheless, those dithiocarbamates (DTCs) are banned for agricultural use in Europe or have expiration at years 2016-2017 because of their highly toxic degradation products and/or metabolites, in particular ethylene thiourea; they found large-scale implementations in materials research and medicine. Despite the broad interdisciplinary of DTC application, due to the above reasons, they have received little attention in the rapidly growing field of analytical chemistry, and in particular, the analytical mass spectrometry. Therefore, the study reported on qualitative, quantitative and structural analysis of ten DTCs (1-10), using the matrix assisted laser desorption/ionization (UV-MALDI)-Orbitrap-mass spectrometry (MS) contributed considerably to the implementation of the method for environmental and foodstuffs monitoring. Its ultrahigh resolving power and capacity for direct solid-state analysis, at limited number of sample pretreatment steps, at concentration levels of analytes of up to femtogram per gram resulted to achievement of a highly precise analytical information for these non-trivial objects. The presented fully validated method and technique is based on the successful ionization of DTCs embedded in three novel organic salts (M1-M3). In this regard, the reported MS and the single-crystal X-ray diffraction data as well as the quantum chemical one are able to correlate the molecular structures in condense and in the gas phase. Despite the novelty of the fundamental methodological character of the research reported, the promising metrology contributed to the applied aspect of the UV-MALDI-MS as a robust analytical method for environmental and foodstuffs monitoring, which is tested on two commercially available crop protecting products such as Mancozeb® and Antracol®, respectively.