Excretion and residues of the pyrethroid insecticide cypermethrin in laying hens

Laying hens were treated daily for 14 days with oral doses of [¹⁴C-phenoxy]cypermethrin (1.52 mg day^?1, 0-7 mg kg^?1) formulated on a small quantity of diet. Radioactivity in the eggs reached a plateau value of 0.05 μg equivalents g^?1 8 days after the start of dosing. Most of the residue was found in the yolk and was a mixture of cypermethrin and material which was closely associated with neutral lipids and phosphatidyl cholines. Four and a half hours after the last dose, the birds were killed and selected tissues were taken for analysis. The highest residue was found in the liver. This was composed of cypermethrin and a mixture of very polar metabolites which were not hydrolysed to significant amounts of 3-phenoxybenzoic acid or its 4-hydroxy derivative.     

Excretion and residues of the pyrethroid insecticide cypermethrin in lactating cows

Two radiolabelled forms of racemic [¹⁴C]cypermethrin (¹⁴C at the benzylic carbon or at C-1 of the cyclopropane ring) were separately administered twice daily to lactating cows in portions of the feed. The amounts dosed were equivalent to 0.2, 5 and 10 μg of cypermethrin per g of feed. The radioactivity eliminated in the milk indicated that the ingestion and elimination of radioactivity were in balance at about day 4 after the start of dosing. Urine and faeces were equally the major routes of elimination, and only a fraction of a percent of the dose appeared in the milk. The residue in the milk was unchanged cypermethrin and was found at a concentration that was proportional to the dose. At the high cypermethrin intake of 10 μg g^?1 of diet, the residue in the milk was 0.03 μg g^?1. Concentrations of residues in the tissues, measured after 7, 20 or 21 days of treatment, were low and in the order: liver>kidney>renal fat>subcutaneous fat>blood>muscle>brain. The major residue in the liver and kidney of a cow that received 10 μg of cypermethrin per g of diet was N-(3-phenoxybenzoyl)glutamic acid. Other conjugates of 3-phenoxybenzoic acid and of 3-(4-hydroxyphenoxy)benzoic acid (unidentified, with the exception of the glycine conjugate) were also present. The residue in fat (about 0.1 μg g^?1 from an intake of 10 μg g^?1 of feed) consisted mainly of cypermethrin.     

A small-scale method for the determination of pyrethroid insecticide residues in crops and soils

A small-scale method for the determination of pyrethroid insecticide residues in crops and soils is described. Compared with the conventional methods, the overall analysis time is reduced by approximately 60% and solvent usage is reduced by approximately 80% using this approach. Results obtained on a range of crops using the small-scale and conventional methods were in good agreement, and a repeatability study showed that the small-scale approach is unbiased and gives good precision. To date, linseed, tobacco, cotton foliage, cotton seed, wheat grain, sorghum, savoy, cauliflower, cabbage, cucumber, apple, peach, blackcurrant, gooseberry, raspberry and soil samples have been analysed using the method. Good recoveries were obtained with all these matrices.     

气相色谱法检测辣椒中7种拟除虫菊酯类农药残留

建立并优化了新鲜辣椒中甲氰菊酯、高效氯氟氰菊酯、氯菊酯、氟氯氰菊酯、氯氰菊酯、氰戊菊酯、溴氰菊酯7种拟除虫菊酯类农药残留的气相色谱(GC-μECD)分析方法。采用50 mL V(乙腈):V(水)=3:1的混合溶剂提取,二氯甲烷萃取, N-正丙基乙二胺(PSA)净化,HP-1毛细管色谱柱分离,气相色谱-电子捕获检测器(GC-μECD)测定。在添加水平为0.017~0.64 mg/kg下的平均回收率为74.0%~105.6%,相对标准偏差为3.3%~15%。该方法准确、灵敏,可同时测定辣椒中7种拟除虫菊酯类农药的残留量。     

Determination of aminozide residues in chrysanthemum tissues

A method initially developed for aminozide [succinic acid mono (2,2 dimethylhydrazide)] determination in apple fruit, involving hydrolysis to unsymmetrical dimethylhydrazine and oxidation of the latter to form aldehyde, has been adapted for use with chrysanthemum tissues. Modifications include preparation of the standard curve from aminozide samples taken through the entire procedure, use of a smaller sample size routine concentration of distillates containing unsymmetrical dimethylhydrazine on a rotary evaporator to remove interfering volatile material and correction for low levels of ‘apparent aminozide’ found in untreated tissue.     

Determination of nitroxynil residues in sheep and calves

A method is described for the determination of nitroxynil (4-cyano-2-iodo-6-nitrophenol) in mammalian tissues. Residues of nitroxynil in the tissues of sheep and calves after subcutaneous administration of the drug are reported.     

Hydrolysis of the pyrethroid insecticide fenpropathrin in aqueous media

The hydrolysis of [¹⁴C] fenpropathrin ( I ) [(RS)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate] was studied in buffer solutions at pH 1.9–10.4, and in natural river and sea water at 25, 40, 55 and 65°C under laboratory conditions. The hydrolysis of I proceeded predominantly through neutral (pH independent) and base-catalysed processes in the regions below pH 3.9 and above pH 7.0, respectively, whereas both reactions occurred between pH 3.9 and 7.0. The rates of hydrolysis of I in buffer solutions were similar to those in one sample of river and one sample of sea water. If this obtains generally, it may be expected that the half-life of I in natural waters, normally within the range pH 5–9, will range from 1.54 to 1080 days at 40°C, 11.3 to 8520 days at 25°C and, by extrapolation of the data obtained in buffer solutions, 106 to 83 000 days at 10°C. The rate constants for hydrolysis of I in aqueous media can be expressed by: Where log k_N = 9.60–(5.56 × 10³ T^?1) and log k_B = 7.32–(2.56 × 10³ T^?1). The calculated rate constants were in good accord with the observed values in buffer solutions. Cleavage of the ester linkage was more rapid than hydration of the cyano group at any pH and temperature tested.     

The metabolic fate in rats of the pyrethroid insecticide WL85871, a mixture of two isomers of cypermethrin

The metabolism of the pyrethroid insecticide WL85871, labelled in the alcohol moiety, has been studied in male and female Wistar rats at a dose of ca 2 mg kg^?1. The compound was rapidly broken down and the radioactivity was mainly eliminated in the urine as the sulphate conjugate of 3-(4-hydroxyphenoxy)benzoic acid (40% of the dose). Some hydroxylation occurred before ester cleavage. Approximately 20% of the ingested compound was not absorbed and was eliminated unchanged in the faeces. There was no evidence for any racemisation of the chiral centres of WL85871 either in the intestine, the faeces or in fat. The small proportion of the dose stored in adipose tissue was eliminated with biphasic kinetics (t½ values, 2–3 days and 17–26 days). The t½ values for skin were, respectively, 2 days and 40 days. As the residue in fat depleted between 3 and 40 days, an increasing proportion (from 28% to 48%) was present as a lipophilic metabolite of WL85871, or of 3-phenoxybenzoic acid, probably a mixture of 3-phenoxybenzoyl diacyl glycerols.     

分散固相萃取-气相色谱法测定茶鲜叶中7种拟除虫菊酯类农药残留

建立了超声波提取、分散固相萃取净化、气相色谱-电子捕获法(GC-ECD)同时测定茶鲜叶中甲氰菊酯、高效氯氟氰菊酯、氯菊酯、氟氯氰菊酯、氯氰菊酯、氰戊菊酯和溴氰菊酯7种拟除虫菊酯类农药残留的方法。样品采用V(乙酸)∶V(乙腈)=1∶99的混合溶剂超声提取,适量乙二胺-N-丙基硅烷(PSA)、十八烷基硅烷键合硅胶(C18)和石墨化碳黑(GCB)吸附剂净化,GC-ECD测定,基质外标法定量。结果表明:在0.004~2 mg/L范围内,7种拟除虫菊酯类农药的峰面积与相应质量浓度间呈良好的线性关系,相关系数均大于0.999;在0.01~0.5 mg/kg的添加水平下,平均回收率为80%~101%,日内相对标准偏差(RSD)均小于8.4%(n=6),日间RSD均小于9.3%(n=3);7种农药在茶鲜叶中的检出限为0.002~0.02 mg/kg,定量限为0.01~0.05 mg/kg。该方法操作简单、定量准确、溶剂用量少,对检测条件要求低,可同时测定茶鲜叶中7种拟除虫菊酯农药的残留量。     

Photodegradation of the pyrethroid insecticide fenpropathrin in water,on soil and on plant foliage

The photodegradation of fenpropathrin [(RS)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate] ( I ), in water, on soil and on plant foliage, was investigated using ¹⁴C-preparations labelled separately at the cyano group, cyclopropyl-C₁ or in the benzyl ring. On exposure to sunlight, I was photodecomposed with initial half-lives of >6 weeks in distilled water, 6.0 weeks in humic acid aqueous solution, 2.7 weeks in river water, 1.6 weeks in sea water and 0.5 of a day in 2% aqueous acetone. A triplet photosensitiser, acetone, together with naturally occurring substances in river and sea water, including humic acid, enhanced the photodegradation of I . On three kinds of soil, I was rapidly photodegraded with initial half-lives of 1–5 days, whereas it was fairly photostable on a mandarin orange leaf. The photoreactions involved were: decarboxylation, hydration of the cyano group to carboxamide, cleavage of the ester or the diphenyl ether linkage, hydrolysis of the carboxamide group to carboxyl, and hydroxylation at either or both of the gem dimethyl groups. The predominant reactions in water were decarboxylation, ester bond cleavage and photo-induced evolution of [¹⁴C] carbon dioxide from the [¹⁴C] cyano label; on soil, hydration or ester bond cleavage predominated. The hydration was also of importance in river and sea water. Decarboxylation did not occur on soil and plant foliage.     

The metabolism of the pyrethroid insecticide cypermethrin in rats; excreted metabolites

The metabolism of the pyrethroid insecticide cypermethrin has been studied in rats using three forms of ¹⁴C-labelling (benzyl-, cyclopropyl- and cyano-) and separate cis- and trans- isomers. The proportion of the dose absorbed from the intestines (50–70% at 2–3 mg kg^?1) is rapidly metabolised and eliminated. The major reaction is cleavage of the ester bond to afford the constituent cis- and trans- acids which are conjugated with glucuronic acid and eliminated in the urine. The 3-phenoxybenzyl portion of the molecule is probably released as the α-hydroxynitrile, which is converted via the aldehyde into 3-phenoxybenzoic acid. This compound is then largely hydroxylated and eliminated as a sulphate conjugate. The cyanide ion is metabolised via predictable routes, for instance, as thiocyanate. Cypermethrin is hydroxylated to some extent before hydrolysis. Most of this hydroxylation occurs at the methyl group trans to the cyclopropane carboxyl group, and at the 4-position of the phenoxy group. cis- Cypermethrin is slightly more stable than the trans-isomer.     

Further studies of the degradation of the pyrethroid insecticide cypermethrin in soils

Studies of the degradation of the pyrethroid insecticide cypermethrin (NRDC 149) and its cis- and trans-isomers (NRDC 160 and NRDC 159, respectively), have been extended. In soils stored in the laboratory for up to 52 weeks, cypermethrin continued to be degraded by hydrolysis and oxidation. A previously unidentified product has now been identified as the dicarboxylic acid 3-(2, 2-dichlorovinyl)-1-methylcyclopropane-1, 2-dicarboxylic acid. Comparative experiments carried out under indoor and outdoor conditions showed that essentially the same products were formed under these different conditions. However, α-carboxy-3-phenoxybenzyl 3-(2, 2-dichlorovinyl)-2, 2-dimethyl-cyclopropanecarboxylate was one minor product detected only under outdoor conditions. Evidence is presented for the further degradation of bound residues arising in soil from cypermethrin treatments. There was limited uptake of the radiolabel into wheat grown in soil containing radiolabelled bound residues.     

超高效液相色谱-电喷雾串联质谱法检测茶叶中8种杀虫剂残留

采用超高效液相色谱-电喷雾串联四级杆质谱仪（UPLC-ESI-MS/MS）,于多反应监测（MRM）模式下建立了茶叶中灭多威、啶虫脒等8种杀虫剂残留的定性及定量分析方法。样品经纯水浸润,乙腈振荡提取,茶叶TPT萃取柱净化,BEH C18柱分离,超高效液相色谱-串联质谱仪测定。结果表明:在0.001~0.5 mg/L质量浓度范围内,各农药峰面积与进样质量浓度间均呈良好的线性关系（r>0.990）,检出限（LOD）为0.000 3~0.01 mg/kg;在国家相关标准规定的添加浓度水平下,各待测农药的平均回收率在61%~107%之间,相对标准偏差（RSD,n=6）为0.2% ~9.9%。该方法准确、可靠、灵敏度高,适用于茶叶中灭多威、啶虫脒等8种杀虫剂残留的检测。     

Synergism between EBI fungicides and a pyrethroid insecticide in the honeybee (Apis mellifera)

The synergistic effect of a range of ergosterol-biosynthesis-inhibiting (EBI) fungicides and a pyrethroid insecticide was studied in the honeybee (Apis mellifera L.). Various EBI fungicides were combined separately with the pyrethroid lambda-cyhalothrin at ratios derived from their recommended application rates to represent tank-mixing in the field. The mixture was then applied topically to the thorax of honeybees, and mortality assessed 24 h post-treatment. All the fungicides tested increased the toxicity of lambda-cyhalothrin to honeybees. The fungicide propiconazole was found to have the strongest synergistic effect, decreasing the LD₅₀ of lambda-cyalothrin from 68.0 ng bee^?1 to 4.2 ng, thus having a synergistic ratio of 16.2. Hazard ratios were calculated for lambda-cyhalothrin and fungicide mixtures using a recommended application rate of 7.5 g a.i. ha^?1. The hazard ratio for lambda-cyhalothrin alone was 110, but when mixed with fungicide synergists, the hazard ratio ranged from 366 with flutriafol to 1786 with propiconazole. A blank formulation of a fungicide (without the active ingredient prochloraz) had little effect on the toxicity of lambda-cyhalothrin, indicating that it is primarily the fungicide active ingredient that is responsible for the synergistic effect. The results are discussed in terms of the potential hazard posed by pesticide synergism to honeybees in the field.     

Organophosphorus insecticide residues in virgin Greek olive oil, 1988–1990

Organophosphorus insecticide residues have been monitored for two years in virgin olive oil after dimethoate and fenthion treatments to control the olive fruit fly. No dimethoate residues were detected in any of the samples. For the first and second years, 50% and 21%, respectively, of the samples contained no detectable fenthion residues, while 4% and 6%, respectively had residue concentrations exceeding the Codex Alimentarious Maximum Residue Limit (1 mg kg^?1). The mean concentration was 0·236 mg kg^?1 oil and the estimated daily intake of fenthion 0·0002 mg kg^?1 body weight (Acceptable Daily Intake 0·001 mg kg^?1 body weight). The parent compound was the most important residue in fresh samples, while aged samples contained a higher amount of the metabolite fenthion sulfoxide. The contribution of the oxygen analogues (P= 0 metabolites) of fenthion to the total residue concentration was<5% in most cases.     

The effects of a new pyrethroid insecticide WL-85871 on foraging honey bees (Apis mellifera L.)

Emulsifiable concentrate formulations of WL-85871 (‘Fastac’) at 10 and 20 g a.i. ha⁻¹, parathion-methyl (MEP) at 500 g a.i. ha⁻¹, and phosalone at 1200 g a.i. ha⁻¹ were individually applied to flowering mustard during June and July 1982. The applications were made by tractor-mounted boom-and-nozzle equipment to small plots in Normandy, France. Before each application, bee hives were placed adjacent to the mustard plots and fitted with either a pollen trap or a dead-bee trap. The application of both dose rates of WL-85871 and phosalone resulted in no increase in bee mortalities and no discernible effect on pollen collection or long-term hive development. In contrast, the application of MEP resulted in substantial bee mortalities, reduced pollen collection and adversely affected hive development. Both dose rates of WL-85871 caused a sharp decline in foraging activity immediately after application, followed by a return to normal activity within a few hours. A prolonged gradual reduction in foraging activity occurred throughout the afternoon period after the phosalone application; with MEP, foraging activity fell rapidly to a very low level and remained so for the rest of that day and the following day. It was concluded that the ground application of WL-85871 at 10 and 20 g a.i. ha⁻¹ had no direct effect on honey bee survival and no observable effect on hive development.