Health risk assessment of neonicotinoid insecticide residues in pistachio using a QuEChERS-based method in combination with HPLC-UV.

There is an increasing need to address the potential risks arising from combined exposures to multiple residues from pesticides in the diet. Pesticide residue-related pollution is a problem that arises because of the increased use of pesticides in agriculture to meet the growing demands of food production. In this study, pesticide residue data were obtained based on an optimized extraction method. For this purpose, we established a method based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction for simultaneous determination of imidacloprid (IMI) and acetamiprid (ACT) in pistachio nuts. The parameters influencing the QuEChERS method were the sample-to-water ratio and adsorbent amounts. As a result, both were optimized to improve the recovery of the analytes as well as the clean-up efficiency of the pistachio matrix. Our results indicated that a freeze-out step and use of primary and secondary amines as an adsorbent led to much cleaner chromatograms with lower baseline drift, without using graphitized carbon black and C18 -based adsorbent, which reduced both cost and time of analysis. Following extraction, the pesticide residues were separated and quantified by reverse-phase HPLC. For validation purposes, recovery studies were carried out using a concentration range from 20 to 2500 µg/L at nine levels. The suitable linearity, precision, and accuracy were obtained with HPLC-UV with recoveries of 70.37%-89.80% for IMI and 81.05%-113.57% for ACT, with relative standard deviations <12%. The validated method was successfully applied to the analysis of pistachio samples collected from a field trial to estimate maximum residue limits. There was no significant health risk for consumers via pistachio consumption.

Rapid, low temperature synthesis of molecularly imprinted covalent organic frameworks for the highly selective extraction of cyano pyrethroids from plant samples.

New imine-linked molecularly imprinted covalent organic frameworks (MICOFs) were successfully prepared, using fenvalerate as the dummy template. Schiff base reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-triformylphloroglucinol was rapidly achieved at room temperature, using Sc(OTf)3 as the catalyst. The surface groups and morphologies of MICOFs were assessed by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area analysis, and scanning electron microscopy. The MICOFs exhibited high selectivity toward four structurally similar cyano pyrethroids, including fenvalerate, flucythrinate, ß-cyfluthrin and λ-cyhalothrin. A method based on solid phase extraction using MICOFs coupled to high performance liquid chromatography was established for the determination of cyano pyrethroids in plant samples. Linearity in the range 0.1-200 ng g-1, with correlation coefficients of 0.9981-0.9993, was obtained for the four cyano pyrethroids. Detection limits and quantification limits were in the range 0.011-0.018 ng g-1 and 0.036-0.060 ng g-1, respectively. Recoveries at three spiked levels ranged from 94.3% to 102.7%. The developed method is thus a promising technique for the selective extraction of cyano pyrethroids from complex matrices.

Determination and Safety Assessment of Residual Spirotetramat and Its Metabolites in Amaranth (Amaranthus tricolor) and Soil by Liquid Chromatography Triple-Quadrupole Tandem Mass Spectrometry.

With the purpose of guaranteeing the safe use of spirotetramat and preventing its potential health threats to consumers, a QuEChERS extraction method coupled with LC triple-quadrupole tandem MS was applied in this study to determine residual spirotetramat metabolites in different tissues of amaranth (Amaranthus tricolor) and in soil. The results indicate that the spirotetramat degraded into different types of metabolites that were located in different tissues of amaranth and in soil. B-keto, B-glu, and B-enol were the three most representative degradation products in the leaf of amaranth, and B-glu and B-enol were the two major degradation products found in the stem of amaranth; however, only B-enol was detected in the root of amaranth. B-keto and B-mono were the two products detected in the soil in which the amaranth grew. The cytotoxicity results demonstrate that spirotetramat and its metabolite B-enol inhibited cellular growth, and the toxicity of spirotetramat and its metabolite B-enol exceeded than that of the metabolites B-keto, B-mono, and B-glu. This investigation is of great significance to the safe use of spirotetramat in agriculture.

Measurement of pyrethroids and their environmental degradation products in fresh fruits and vegetables using a modification of the quick easy cheap effective rugged safe (QuEChERS) method.

Pyrethroid insecticides are used extensively in agriculture, and they, as well as their environmental degradates, may remain as residues on foods such as fruits and vegetables. Since pyrethroid degradates can be identical to the urinary markers used in human biomonitoring, it is important to understand the contribution of these degradates when studying sources of human pyrethroid exposure. We modified the widely used Quick Easy Cheap Effective Rugged Safe (QuEChERS) method to measure several current-use pyrethroids (cis/trans-permethrin, cypermethrin, deltamethrin, esfenvalerate, bifenthrin, cyfluthrin, and cyhalothrin) and their environmental degradation products (3-PBA, cis/trans-DCCA, 4-F-3-PBA, DBCA, and MPA) in selected fresh fruits and vegetables. Using fortified samples, we determined extraction efficiencies from: tomatoes, oranges (whole, peeled, and rind), grapes, apples, bananas (peeled and rind only), onions, lettuce, green peppers, carrots and broccoli. For a subset of these food items (apples, grapes, tomatoes, lettuce and banana peel), we also established limits of detection (MDLs) and quantitation (MQLs). Each sample was homogenized (1kg) then spiked with the target pyrethroids and their degradation products. Sub-samples (15g) were extracted with acetonitrile, then salted out and partitioned with NaCl and MgSO4. The extract was divided and further cleaned using solid phase extraction (SPE) cartridges containing either graphitized non-porous carbon (pyrethroids) or C18 (degradation products). Sample analysis was via liquid chromatography/tandem mass spectrometry (LC-MS/MS). Considering the mean recoveries each of the 14 analytes in all 13 matrices: 42% of the recoveries were ≥90%, 70% were ≥80%, and 90% were ≥70%. All MDL's were less than 100ng/kg, except 3-PBA (132ng/kg, tomato), MPA (129ng/kg, tomato), and trans-permethrin (141ng/kg, banana peel). We then applied the method to non-spiked samples (subset of 5 for which the MDLs/MQLs had been determined) collected weekly for four weeks from local supermarkets. At least one pyrethroid was present in measureable concentrations in all matrices except banana peels. In contrast, the only degradation products detected were cis/trans-DCCA, in one lettuce sample.

Cost-effective medium for the production of mosquito pupicidal lipopeptide from Bacillus subtilis subsp. subtilis (VCRC B471).

BACKGROUND & OBJECTIVES: A cyclic lipopeptide (CLP), surfactin produced by a strain of Bacillus subtilis subsp. subtilis (VCRC B471) was found to exhibit mosquitocidal activity. The present study was carried out to enhance the surfactin level using low cost material in the production medium. METHODS: Two carbon sources, glucose and common sugar, and two nitrogen sources, ammonium nitrate and soya were used in the study. Different concentrations of 'C' and 'N' sources were used in the production medium to enhance the production of surfactin. RESULTS: A new medium (SS7) containing 2% sugar, 6% soya and 0.5% common salt with micronutrients was designed which was found to enhance the production of surfactin. The crude mosquitocidal metabolite (CMM) produced in this medium was 3 g/l which was two times higher than that obtained using synthetic medium NYSM. The LC50 dosage of the CMM to the pupal stages of An. stephensi (2.3 µg/ml) was comparable to that obtained with CMM from the conventional medium. INTERPRETATION & CONCLUSION: The newly designed cost-effective medium designated as sugar soya medium (SSM) enhanced the production of surfactin and the cost of production was estimated as [symbol: see text] 6 per litre, which is six times lesser than that of the conventional medium. Replacement of sodium chloride with cooking salt further reduced the cost of the medium.

Old ingredients for a new recipe? Neem cake, a low-cost botanical by-product in the fight against mosquito-borne diseases.

Mosquitoes (Diptera: Culicidae) represent an important threat to millions of people worldwide, since they act as vectors for important pathogens, such as malaria, yellow fever, dengue and West Nile. Control programmes mainly rely on chemical treatments against larvae, indoor residual spraying and insecticide-treated bed nets. In recent years, huge efforts have been carried out to propose new eco-friendly alternatives, with a special focus on the evaluation of plant-borne mosquitocidal compounds. Major examples are neem-based products (Azadirachta indica A. Juss, Meliaceae) that have been proven as really effective against a huge range of pests of medical and veterinary importance, including mosquitoes. Recent research highlighted that neem cake, a cheap by-product from neem oil extraction, is an important source of mosquitocidal metabolites. In this review, we examined (i) the latest achievements about neem cake metabolomics with special reference to nor-terpenoid and related content; (ii) the neem cake ovicidal, larvicidal and pupicidal toxicity against Aedes, Anopheles and Culex mosquito vectors; (iii) its non-target effects against vertebrates; and (iv) its oviposition deterrence effects on mosquito females. Overall, neem cake can be proposed as an eco-friendly and low-cost source of chemicals to build newer and safer control tools against mosquito vectors.

Assessment of residual bio-efficacy and persistence of Ipomoea cairica plant extract against Culex quinquefasciatus Say mosquito.

Specification on residual action of a possible alternative insecticide derived from plant materials is important to determine minimum interval time between applications and the environmental persistence of the biopesticides. The objective of this study is to evaluate crude acethonilic extract of Ipomoea cairica leaves for its residual and persistence effects against Culex quinquefasciatus larvae. Wild strain of Cx. quinquefasciatus larvae were used for the purpose of the study. Two test designs, replenishment of water and without replenishment of water were carried out. For the first design, a total of 10 ml of test solution containing Ip. cairica extracts was replenished daily and replaced with 10 ml of distilled water. For the second design, treatment water was maintained at 1500 ml and only evaporated water was refilled. Larval mortality was recorded at 24 hours post-treatment after each introduction period and trials were terminated when mortality rate falls below 50%. Adult emergences from survived larvae were observed and number of survivals was recorded. For the non-replenishment design, mortality rate significantly reduced to below 50% after 28 days, meanwhile for replenishment of water declined significantly after 21 days (P < 0.05). There was no adult emergence observed up to seven days for non-replenishment and first two days for replenishment of water design. The short period of residual effectiveness of crude acethonilic extract of Ip. cairica leaves with high percentage of larval mortality on the first few days, endorses fewer concerns of having excess residues in the environment which may carry the risk of insecticide resistance and environmental pollution.

Entomopathogenic marine actinomycetes as potential and low-cost biocontrol agents against bloodsucking arthropods.

A novel approach to control strategies for integrated blood-feeding parasite management is in high demand, including the use of biological control agents. The present study aims to determine the efficacy of optimized crude extract of actinomycetes strain LK1 as biological control agent against the fourth-instar larvae of Anopheles stephensi and Culex tritaeniorhynchus (Diptera: Culicidae) and adults of Haemaphysalis bispinosa, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae), and Hippobosca maculata (Diptera: Hippoboscidae). Antiparasitic activity was optimized using the Plackett-Burman method, and the design was developed using the software Design-Expert version 8.0.7.1. The production of the optimized crude actinomycetes LK1 strain extract was performed using response surface methodology to optimize the process parameters of protease inhibitor activity of marine actinobacteria for the independent variables like pH, temperature, glucose, casein, and NaCl at two levels (-1 and +1). The potential actinomycetes strain was identified as Saccharomonas spp., and the metamodeling surface simulation procedure was followed. It was studied using a computer-generated experimental design, automatic control of simulation experiments, and sequential optimization of the metamodels fitted to a simulation response surface function. The central composite design (CCD) used for the analysis of treatment showed that a second-order polynomial regression model was in good agreement with the experimental results at R (2) = 0.9829 (p < 0.05). The optimized values of the variables for antioxidant production were pH 6.00, glucose 1.3%, casein 0.09%, temperature 31.23 °C, and NaCl 0.10%. The LK1 strain-optimized crude extract was purified using reversed-phase high-pressure liquid chromatography, and the isolated protease inhibitor showed antiparasitic activity. The antiparasitic activity of optimized crude extract of LK1 was tested against larvae of A. stephensi (LC50 = 31.82 ppm; r(2) = 0.818) and C. tritaeniorhynchus (LC50 = 26.62 ppm; r(2) = 0.790) and adults of H. bispinosa (LC50 = 106.58 ppm; r(2) = 0.871), R. (B.) microplus (LC50 = 92.96 ppm; r(2) = 0.913), and H. maculata (LC50 = 84.90 ppm; r(2) = 0.857).

Dengue vector management using insecticide treated materials and targeted interventions on productive breeding-sites in Guatemala.

BACKGROUND: In view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies particularly for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites. METHODS: The study was conducted as a cluster randomized community trial using "reduction of the vector population" as the main outcome variable. The trial had two arms: 10 intervention clusters (neighborhoods) and 10 control clusters in the town of Poptun Guatemala. Activities included entomological assessments (characteristics of breeding-sites, pupal productivity, Stegomyia indices) at baseline, 6 weeks after the first intervention (coverage of window and exterior doorways made of PermaNet 2.0 netting, factory treated with deltamethrin at 55 mg/m2, and of 200 L drums with similar treated material) and 6 weeks after the second intervention (combination of treated materials and other suitable interventions targeting productive breeding-sites i.e larviciding with Temephos, elimination etc.). The second intervention took place 17 months after the first intervention. The insecticide residual activity and the insecticidal content were also studied at different intervals. Additionally, information about demographic characteristics, cost of the intervention, coverage of houses protected and satisfaction in the population with the interventions was collected. RESULTS: At baseline (during the dry season) a variety of productive container types for Aedes pupae were identified: various container types holding >20 L, 200 L drums, washbasins and buckets (producing 83.7% of all pupae). After covering 100% of windows and exterior doorways and a small number of drums (where the commercial cover could be fixed) in 970 study households, tropical rains occurred in the area and lead to an increase of the vector population, more pronounced (but statistically not significant) in the control arm than in the intervention arm. In the second intervention (17 months later and six weeks after implementing the second intervention) the combined approach of ITMs and a combination of appropriate interventions against productive containers (Temephos in >200 L water drums, elimination of small discarded tins and bottles) lead to significant differences on reductions of the total number of pupae (P = 0.04) and the House index (P = 0.01) between intervention and control clusters, and to borderline differences on reductions of the Pupae per Person and Breteau indices (P = 0.05). The insecticide residual activity on treated curtains was high until month 18 but the chemical concentration showed a high variability. The cost per house protected with treated curtains and drum covers and targeting productive breeding-sites of the dengue vector was $ 5.31 USD. The acceptance of the measure was generally high, particularly in families who had experienced dengue. CONCLUSION: Even under difficult environmental conditions (open houses, tropical rainfall, challenging container types mainly in the peridomestic environment) the combination of insecticide treated curtains and to a less extent drum covers and interventions targeting the productive container types can reduce the dengue vector population significantly.

A rapid and inexpensive bioassay to evaluate the decontamination of organophosphates.

An inexpensive and rapid bioassay using adult red flour beetles was developed for use in assessing the decontamination of environments containing organophosphates and related chemicals. A decontamination protocol was developed which demonstrated that 2 to 3 applications of 5% bleach solution were required to obtain nearly complete decontamination of malathion. The bioassay was also used to screen common household cleaners as potential decontaminating agents, but only 5% bleach was effective at improving survival of insects on steel plates treated with 25% malathion. A toxic degradation product (malaoxon) was detected using gas chromatography/mass spectrophotometry; this toxin affected the decontamination efficacy and resulted in continued toxicity to the beetles until subsequent decontaminations. The bioassay provides evidence to support the use of red flour beetles as a sensitive, less expensive method for determining safety levels of environments contaminated with malathion and other toxins, and may have application in the study of chemical warfare agents.