Lia Emi Nakagawa

OPTIMIZING MICROWAVE-ASSISTED SOLVENT EXTRACTION (MASE) OF PESTICIDES FROM SOIL

Microwave-assisted solvent extraction (MASE) was investigated as an alternative for extraction of parathion (O,O-diethyl O-4-nitrophenyl phosphorothioate), methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate), p,p′-DDE [1,1′-dichloro-2,2-bis(4-chlorophenyl)ethane], hexachloro-benzene (HCB), simazine (6-chloro-N 2,N 4-diethyl-1,3,5-triazine-2,4-diamine) and paraquat dichoride (1,1′-dimethyl-4,4′-bipyridinium) from two different soils and from an earthworm-growing substrate. The matrices were fortified with 14C-radiolabeled pesticides and extracted with various solvent systems under different microwave conditions. Recoveries of more than 80% could be obtained depending on the used microwave conditions and solvent, except for paraquat whose recovery was generally less efficient. Thus, MASE can be successfully used to extract pesticides from environmental and biological samples and could be a viable alternative to conventional extraction methods. The technique uses smaller amounts of organic solvents, thereby minimizing the costs of the analysis and the disposal of waste solvent.

Behavior of atrazine in soils of tropical zone

Abstract Movement and degradation of 14C‐atrazine (2‐chloro 4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine, was studied in undisturbed soil columns (0.50m length × 0.10m diameter) of Gley Humic and Deep Red Latosol from a maize crop region of Sao Paulo state, Brazil. Atrazine residues were largely confined to the 0–20cm layers over a 12 month period Atrazine degraded to the dealkylated metabolites deisopropylatrazine and deethylatrazine, but the major metabolite was hydroxyatrazine, mainly in the Gley Humic soil. Activity detected in the leachate was equivalent to an atrazine concentration of 0.08 to 0.11μg/1. The persistence of 14C‐atrazine in a maize‐bean crop rotation was evaluated in lysimeters, using Gley Humic and Deep Red Latosol soils. Uptake of the radiocarbon by maize plants after 14‐days growth was equivalent to a herbicide concentration of 3.9μg/g fresh tissue and was similar in both soils. High atrazine degradation to hydroxyatrazine was detected by tic of maize extracts. After maize harvest, w...

Multiresidue Screening Methods for the Determination of Pesticides in Tomatoes

The possibility of applying thin layer chromatography (TLC) detection for the analysis of pesticide residues in tomatoes was investigated. Samples of tomatoes that have never been treated with pesticide were fortified with atrazine, carbaryl, carbofuran, chloroxuron, diuron, dimethoate, imazalil, oxamyl and methamidophos. The samples were extracted, cleaned‐up by gel permeation chromatography and then applied on silica gel plates. The pesticides were eluted with ethyl acetate and dichloromethane. Two eluting solvent systems were tested, one using the reagents o‐ toluidine + potassium iodite (o‐TKI) and the other p‐ nitrobenzene fluoroborate (NBFB). After the development of the plates, the diameter of the spots was measured. The lowest minimum detection quantity (MDQ) for o‐TKI system for atrazine was 12 ng. The highest was 125 ng for carbofuran. Using NBFB system, the lowest MDQ was 60 ng for carbaryl and the highest was 70 ng obtained for carbofuran. Considering the concentration of these pesticides in the spiked tomato samples, the minimum concentration was 1.1 ng/µL and 32.3 ng/µL for atrazine and carbofuran, respectively, by using o‐TKI system. For NBFB system the minimum concentration reached was 3.5 ng/µL and 4.3 ng/µL for carbaryl and carbofuran, respectively. This study showed that TLC can be used for semi‐quantitative analysis.

Análise de resíduos de pesticidas em tomates por cromatografia em camada delgada

Pesticide residues are determined by thin layer chromatography (TLC) using the Hill reaction as a detection method. Tomatoes samples without pesticide were fortified with atrazine, diuron, chloroxuron and metribuzin, and were applyed in silica gel plates with the help of a microsyringe. The pesticides were elued with ethyl acetate. There was no need of cleaning up because no interference was noticed. After the revelation of the plates, the diameters of the spots were measure by using a rule. The range of the determined concentration for all the pesticides was from 0.1 to1.0 ng/mL. The results obtained through TLC can be used for semi-quantitative analysis.The results obtained were compared to gas and liquid chromatography, showing good agreement between both techniques.

Palatability and efficacy of bromadiolone rodenticide block bait previously exposed to environmental conditions.

BACKGROUND In São Paulo city, rodent infestation is considered to be a serious public health problem and is the object of a municipal rodent control programme. One of the most important routine methods involves baiting in sewers, using bromadiolone block bait in a pulsed baiting strategy. It has been observed that, after each pulse, bait is not always consumed, and its appearance is altered, which has led to concerns about efficacy. We assessed whether exposure to sewer conditions influences the palatability and efficacy of rodenticide baits to Norway rats (Rattus norvegicus). Baits containing bromadiolone as active ingredient were placed in sewers, removed after 30 days and offered to rats in a two-choice food trial and a no-choice food trial. RESULTS The appearance of the rodenticide baits changed after 30 days exposure to sewer conditions, but they continued to be palatable and effective against rats. The level of mortality was considered to be satisfactory, 75% in the two-choice food trial and 100% in the no-choice food trial. CONCLUSION Results support the reuse of rodenticide block bait in rodent control. It seems to be justified to continue using/reuse baits even when their appearance has changed after 30 days exposure in sewer systems.

Pyrethroid concentrations and persistence following indoor application

Residential indoor environments are potential sources of exposure to pyrethroids, which have low acute toxicity to humans but are allergenic and suspected endocrine disruptors. The present study evaluated the persistence of the pyrethroids cypermethrin and beta-cyfluthrin on indoor surfaces and in house dust. Cypermethrin and beta-cyfluthrin were applied and maintained on aluminum foils and in dust samples for 112 d under controlled conditions and for 12 mo in a test house; periodically, they were quantified by high-performance liquid chromatography. Cypermethrin and beta-cyfluthrin concentrations showed decreases of 10.1% and 7.7% on aluminum foils, and 12.7% and 16.4% in dust, respectively, at 112 d under controlled conditions. In the test house, cypermethrin and beta-cyfluthrin concentrations decreased by 40.3% and 60.2% on aluminum foils, and 29.6% and 56.2% in dust at the end of the study. The results show the considerable persistence of cypermethrin and beta-cyfluthrin indoors and indicate the risk of exposure to these products. Environ Toxicol Chem 2017;36:2895-2898.

Persistência do inseticida clorpirifós no ar em casa de vegetação

Arq. Inst. Biol., v.83, 1-4, e1052014, 2016 RESUMO: Os inseticidas organofosforados estão entre os agrotóxicos de maior toxicidade aguda disponíveis no mercado e são usados em várias regiões do Brasil. Avaliaram-se a concentração e o tempo de permanência do inseticida organofosforado clorpirifós no ar, após aplicação em uma casa de vegetação. O clorpirifós permaneceu no ar da casa de vegetação em concentração três vezes acima do limite de exposição ocupacional por mais de 24 horas, e ainda foi detectado após quatro dias.Organophosphate pesticides are among those with the highest acute toxicity and are available on the market and used in several regions of Brazil. The concentration and residence time of the organophosphate pesticide, chlorpyrifos, in the air after application in a greenhouse were investigated. For more than 24 h, the chlorpyrifos remained in the greenhouse air at concentrations three times above the occupational exposure limit and was still detectable four days later.