Residues of tetrachlorvinphos and its breakdown products on treated crops. I.—Method development

Procedures are described for the analysis of crops for residues of tetrachlorvinphos (Gardona, trans-isomer of dimethyl 1-(2′,4′,5′-trichlorophenyl)-2-chloroyinyl phosphate) insecticide together with methods for the analysis for residues of its isomer and its conjugated and non-conjugated breakdown products. Suitable procedures for the extraction are described together with procedures for the cleanup of the extracts by partition or column chromatography and final analysis down to 0·01 ppm or less by gas-liquid chromatography with electron capture detection.     

Residues of tetrachlorvinphos and its breakdown products on treated crops. II.—Residues on apples

Apples treated with tetrachlorvinphos (Gardona, trans-isomer of dimethyl 1-(2′,4′,5′-trichloropheny1)-2-chlorovinyl phosphate) insecticide under field conditions in several countries in 1965, 1966 and 1967 have been analysed at intervals after treatment for residues of tetrachlorvinphos itself, its cis-isomer and seven potential breakdown products. Residues of up to 10 ppm of tetrachlorvinphos were detected immediately after the last of three applications of tetrachlorvinphos (diluted to 0.16% active material). The initial half-life of the tetrachlorvinphos was on average about 0.5 weeks under U.K. conditions and only 10% of the tetrachlorvinphos remained unchanged at 2 weeks after application. The overall chemical persistence of the wettable powder formulation was not significantly different from that of the emulsifiable concentrate formulation. Within 8 weeks of the application the residues were mainly of tetrachlorvinphos itself, its cis-isomer and the alcohol 1-(2′,4′-5′-trichlorophenyl)ethan-l-ol, in free and sugar-conjugated forms. The residues of the conjugates of this alcohol (up to 0.92 ppm) were generally present in higher concentration at 6-8 weeks after the application than were the residues of the other components. Whilst residues of other breakdown products were detected on the apples their individual residues were below 0.05 ppm and generally below 0.01 ppm at 6 weeks or more after the last of several applications of tetrachlorvinphos.     

Determination of residues in apples and pears following treatment with the acaricide fenazaflor II. Method for individual residues of fenazaflor and its hydrolysis product

The occasional need for separation of residues of fenazaflor and its hydrolysis product, instead of determination of the total residue by the routine method, is satisfied by partition of the extract between hexane and acidified aqueous methanol. Both residues are subsequently determined as the hydrolysis product by GLC with electron capture detection, after hydrolysis of fenazaflor.     

Pesticide residues in foodstuffs in Great Britain. XV.—Triphenyltin residues in potatoes

An analytical method and results are given for the determination of triphenyltin residues in potatoes. Of the 44 samples analysed 35 contained residues of 0.001 ppm or less; residues in 6 of the samples were in the range 0.002–0.005 ppm and in 3 samples in the range 0.006–0.008 ppm.     

Pesticide residues in foodstuffs in Great Britain XIV.—Mercury residues in potatoes

The total mercury contents of the skin and flesh fractions of potatoes from 87 commercial crops grown in England were in the range 0.0–0.08 ppm with the majority in the range 0.01–0.04 ppm.     

Pesticide residues in the total diet in England and Wales, 1966–1967: III.—Organophosphorus pesticide residues in the total diet

Details are given of the methods of analysis used in the determination of Organophosphorus pesticide residues in each of the food groups into which the total diet samples were divided. Residues of only 6 pesticides were detected. Malathion was the most commonly found, mainly in the cereal foods group of the diet, but all the residues were at low levels.     

Residues of tetrachlorvinphos and its breakdown products on treated crops. III.—Residues on a range of field crops

A wide range of crops including top fruit, cereals, brassicas, root vegetables and cotton from field trials in several countries in 1965, 1966, 1967 and 1968 have been analysed for residues of tetrachlorvinphos (Gardona, trans-homer of dimethyl 1-(2′,4′,5′-trichlorophenyl)-2-chlorovinyl phosphate) foliar insecticide, its isomer and its potential breakdown products. The residues under field conditions were mainly of tetrachlorvinphos, its isomer and 1-(2′,4′,5′-trichlorophenyl)ethan-1-ol in free and sugar-conjugated forms. Tetrachlorvinphos was not unduly persistent on the crops and its initial half-life varied from 2 days on cabbage, to 7 days on potato foliage and to 12 days on pears (after the last of five applications). From one week after the final application onwards the highest residues of tetrachlorvinphos observed were on olives (1 ppm after 18 days after a single application of 0·1 % active material), maize leaf (2·8 ppm at 9·5 weeks after the last of two applications at 3 kg/ha), and cabbage (1·9 ppm at 12 days after the last of three applications at 0·5 kg/ha). The maximum residues of the alcohol in the free form were 3·2 ppm on maize leaf at 8 weeks from the second application at 1·5 kg/ha and in the conjugated form were 1·0 ppm on cauliflowers at 6 days after the last of four applications at 0·5 kg/ha.     

Pesticide residues in foodstuffs in Great Britain: XIII.—Organochlorine residues in cereals,pulses and nuts

Results are presented for the determination of organochlorine insecticide residues in grain, pulses and nuts sampled on arrival in Britain during the 2½ years up to June 1969. BHC was detected in nearly every sample but the general level was low, most samples containing less than 0·1 ppm. DDT was found less frequently. Very few samples contained more than 1 ppm of either insecticide. DDE in trace amounts was found in about 10% of the samples of grain and nuts and TDE was found in one sample of grain. The only other organochlorine compounds detected were aldrin in one sample of pulses and hexachlorobenzene in 7 samples of wheat.     

Estimation of residues of the molluscicide,niclosamide, in bananas by gas—liquid chromatography of the heptafluorobutyryl derivative of the substituted aniline moiety

A sensitive method for the detection and estimation of residues of the molluscicide, niclosamide, in bananas is described. The procedure involves extraction of the molluscicide, purification of the extract by solvent partition and column chromatography, formation of the heptafluorobutyryl derivative of 2-chloro-4-nitroaniline in 99% yield and determination of the derivative by gas—liquid chromatography with electron-capture detection. Recoveries from fortified bananas were 89 and 79% at levels of 0.02 and 0.2 mg kg^?1, respectively. The sensitivity of the method was such that 0.6 pg of the pure derivative could be detected, based on twice the background noise level on the chromatograph.     

Pesticide residues in the total diet in England and Wales, 1966–1967: IV.—Mercury content of the total diet

Results are given of determinations of the mercury content of each of the 7 composite food groups into which samples of the total diet were divided. In the very few sub-samples in which mercury was detected, the levels found were very low and close to the limit of detection by the colorimetric method used.     

Movement of dieldrin through soils: I.—From arable soils into ponds

Dieldrin at a rate of 22–45 kg active ingredient/ha (10–20 times the rate used in practice) was applied to strips, each 1·8–3·6 m wide, 3·6–4·5 m away from the edges of four ponds. There were shallow to steep slopes from the treated strips towards the ponds. Dieldrin was found in small amounts in untreated soil on the surface of the slopes between the treated strips and the ponds but none was found in the pond water. Very small amounts (maximum 0·3 ppm) were found in bottom mud of ponds but not when the dieldrin had been thoroughly incorporated into the treated soil after application. In the experiment where the vertical distribution of dieldrin was studied the largest amount below 15 cm was 1·1 ppm at 81 weeks from application.     

The behaviour of residues of benzoylprop-ethyl and its breakdown products in wheat

Samples of wheat grain and straw have been analysed from trials with the wild oat herbicide benzoylprop-ethyl ( I ) in several countries. Following recommended commercial treatments (application of 1.0–1.6 kg ha^?1 at Feekes growth stage G-J), total residues of I and its hydrolysis product N-benzoyl-N-(3,4-dichlorophenyl)-DL - alanine (free and conjugated) were low and in the majority of instances they were < 0.01 mg kg^?1 in samples of grain from the UK, although rather higher residues were detected in some grain samples from other countries. Residues in straw were higher, but normally did not exceed 2 mg kg^?1, and were rather variable, possibly as a result of differences in agricultural practice.     

The behaviour of residues of flamprop-isopropyl and its breakdown products in barley

Residue data are reported for flamprop-isopropyl ( I ) in barley grain and straw samples following applications of the herbicide to crops grown in eight countries. The samples were analysed for I and its hydrolysis product N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL -alanine ( II ). Following recommended applications (normally 1 kg ha^?1 at Feekes scale G-I/J), residues of I and II in the grain were low (90% were <0.02 mg kg^?1 for I , 86% were <0.06 mg kg^?1 for II , levels which were essentially the limits of determination). Residues in straw were higher and more variable, but again 63 and 77% of samples were below 1 mg kg^?1 for I and II , respectively.     

Theory,preparation and ‘exhaustion’ on wool fibres of pesticide emulsions. I.—Theory of the stability of pesticide emulsions

Emulsifiable concentrates containing toxic agents are usually formulated with blends of anionic and non-ionic surfactants which determine the structure of the interfacial layer enveloping the suspended droplets. Electrostatic repulsion and London-van der Waals attraction decide their flocculation whereas other properties of the interfacial layer may also play an important part in their coalescence.     

Pesticide residues in the total diet in Canada. III—1971

Foods, representing an average Canadian diet, were cooked, grouped by type of product and made into composites which were then analysed for organochlorine and organophosphorus pesticides and arsenic. The amounts found were at a consistently low level and would contribute approx. 22 μg total pesticide residues and 25 μg arsenic/person/day.     

Determination of residues of isofenphos and its phosphoramidate analogue

A method is described for the gas chromatographic determination of residues of isofenphos (BAY 92114, O-ethyl O-2-isopropoxycarbonylphenyl isopropylphosphor-amidothioate) and its phosphoramidate which is a potential metabolite. When potato, cabbage, rapeseed and a sandy loam soil were fortified with 0.01, 0.1 and 1.0 mg/kg and analysed by the method described, the recoveries ranged from 76 to 98%. The limits of detection of the method were 0.5 and 1.0 ng for isofenphos and isofenphos oxygen analogue respectively. Degradation under field conditions of isofenphos to its oxygen analogue was demonstrated in a sample of field-treated potatoes.     

Interactions between tri-S-butyl phosphorotrithioate (DEF) and growth regulator herbicides: I.—A preliminary report

Mixtures of tri-S-butyl phosphorotrithioate (DEF) emulsion and the potassium salt of picloram were strongly synergistic when applied as foliar sprays to pot-grown privet, poplar, guava and Eucalyptus plants. A similar but less marked effect was observed in privet, using mixtures of DEF and a water-soluble amine formulation of 2,4,5-T. By contrast, mixtures of an oil-soluble ester formulation of 2,4,5-T with DEF were antagonistic with privet.     

Determination of dimetridazole in pig tissue I. Method

A method is described for the determination of dimetridazole (1,2-dimethyl-5-nitroimidazole) in pig tissues. The final estimation is made by direct current polarography.     

Development of methods for the analysis of crops and soils for residues of benzoylprop-ethyl and its breakdown products

Methods are described for the analysis of residues of the herbicide benzoylpropethyl, ethyl (±)-2-[ N-(3,4-dichlorophenyl)benzamido]propionate, and its breakdown product, (±)-2-[ N-(3,4-dichlorophenyl)benzamido]propionic acid, in wheat and soil. In wheat the acid degradation product conjugates with plant sugars and the present paper includes methods for determination of these residues either separately or as a combined residue with unconjugated acid. Efficient extraction procedures have been developed together with partition and column chromatographic techniques for purification of extracts. The full analytical procedures are described and the final determinations are by g.1.c. with electron capture detection with blank values for field samples in the range 0.01–0.05 mg/kg. Good recoveries were obtained. Radiochemical techniques have been used to verify the extraction and subsequent procedures in the methods.     

The pyrethrins and related compounds: X.—The methylbenzyl chrysanthemates

New or improved routes are used to prepare all the nineteen methylbenzyl chrysanthemates, including 2,4,6-trimethylbenzyl (+) and (?)-trans-chrysanthemates, 2,3,4,6-tetramethyl-and 2,3,4,5,6-pentamethyl-benzyl chrysanthemates, and the chrysanthemates of the new alcohols, 2,3,5-and 3,4,5-trimethylbenzyl alcohols.