High Pressure Liquid Chromatography of Captan in Formulations: Collaborative Study

A simple method for measuring captan was tested by 18 collaborators. Formulations are extracted with methylene chloride which contains diethyl phthalate as an internal standard, and detected at 254 nm after high pressure liquid chromatographic separation in a 25 cm × 4 mm column packed with 10 µm silica gel. After inert materials are removed, the supernate is added directly to the column with methylene chloride as the mobile phase; peak height ratios are used for quantitation. Most pesticides commonly formulated with captan do not interfere. Retention times and UV response factors relative to captan are listed for 34 pesticides formulated with captan. The collaborators made single determinations on 6 samples (3 pairs of duplicates). The coefficients of variation were 0.67% for the technical, 1.16% for the 50% wettable powder, and 1.71% for the 5% dust. Several collaborators were unable to separate carbaryl and diethyl phthalate on a combination dust containing captan, dicofol and carbaryl; therefore, the method has been adopted as official first action only for captan formulations containing no other active ingredients.

Gas-Liquid Chromatographic Method for the Analysis of Microencapsulated Ethyl Parathion and Methyl Parathion Insecticides: Collaborative Study

The determination of ethyl parathion in Penncap-E insecticide was studied collaboratively by 14 laboratories. The assay of methyl parathion in Penncap-M insecticide was studied by 8 laboratories. The original method which was adopted official first action for methyl parathion specified dimethoate, which is currently classified as a suspected carcinogen, as the internal standard. The current collaborative efforts were conducted as a supplemental study to evaluate the performance of the new internal standard, bis-2-methoxyethyl phthalate, and to test the gas-liquid chromatographic method for microencapsulated ethyl parathion (internal standard, dibutyl phthalate). The method uses essentially the same grinding and extraction with acetonitrile as the original study. At the 20% methyl parathion level, the standard deviation within laboratories was 0.186%, and among laboratories, 0.737%. Two formulations of ethyl parathion at approximately 16 and 24% were analyzed in replicate on 2 days by the same analyst, and provided excellent agreement within laboratories as well as among laboratories. The standard deviation (pooled) within laboratories was 0.284% and among laboratories, 0.518%. The method has been adopted as official first action.

Sex pheromones produced by male boll weevil: isolation, identification, and synthesis

The response of female boll weevils to males, Anthonomus grandis Boheman, in laboratory bioassays can be reproduced by exposure to a mixture of compounds I, II, and either III or IV, all isolated from male weevils and their fecal material. The same response was elicited by mixtures of tile synthesized coimpounds. Compound I is (+)-cis-2-isopropenyl-l-methylcyclobtutaneethanol; II, cis-3,3-dimethiyl->(1,beta)cyclohexaneethanol; III, cis-3,3-dimethlyl->(1,alpha)-cyclohexaneacetaldehyde; and IV, trans-3,3-dimethyl->(1,alpha)-cyclohexanecetaldehyde.

State findings on pesticide residues in food--1988 and 1989

Findings of pesticide and related chemical residues are presented for 27,065 samples of foods collected and analyzed in 10 state food laboratories over 1988 and 1989 (fiscal years (FY) 88 and 89). These laboratories conduct food regulatory programs compatible with national programs of the U.S. Food and Drug Administration. Of the findings, 6325 samples contained detectable levels of 1 or more pesticide analytes and 418 (or 1.5%) of the total number of samples were deemed to be of regulatory significance.

State programs for pesticide residues in foods

Two U.S. data collection and dissemination programs, FEEDCON and FOODCONTAM, are described. FEEDCON provides information on contamination levels in animal feeds of toxic chemical residues (pesticides, industrial chemicals, heavy metals, mycotoxins, natural plant toxins, salmonella, and therapeutic drug cross-contaminations). FEEDCON data are collected from approximately 40 state feed regulatory agencies, feed manufacturers, and related groups who subscribe ($100-$200 per year) to the program, which is sponsored by the Association of American Feed Control Officials. FOODCONTAM provides similar information, but is limited to pesticides, heavy metals and industrial chemicals (polychlorinated and polybrominated biphenyls, etc.) in human foods. Both programs have been developed and initiated under U.S. Food and Drug Administration contracts with the Mississippi State Chemical Laboratory. Program structures of both are outlined conceptually, and FOODCONTAM is described in detail. FOODCONTAM data-sharing program development is essentially complete, but expansion by incorporating FDA data with State Laboratory data is nearing reality.

Liquid Chromatographic Determination of Bendiocarb in Technical Materials and Wettable Powder Formulations: Collaborative Study

A liquid chromatographic method for determination of bendiocarb in technical materials and wettable powders was tested by 12 collaborators. Bendiocarb is dissolved in acetonitrile containing 0.1% propiophenone as internal standard. This solution is analyzed on a liquid chromatograph utilizing a reverse phase (C18) column. The compound is detected at 254 nm and peak area is used for quantitation. The 3 different materials studied contained 20, 80, and nominally 100% bendiocarb. Each was examined in duplicate to provide the necessary matched pairs. Collaborators approved of the ease and simplicity of the method and, in particular, the way the method can be applied to automatic injection assemblies. The statistical data show acceptable precision of the method: Reproducibility coefficients of variation were 20% material, 2.04%; 80% material, 1.02%; and nominal 100% material (technical product), 0.64%. The method has been adopted official first action.

Gas Chromatographic Determination of Metribuzin in Formulations: Collaborative Study

A collaborative study was conducted on a gas chromatographic method for determining metribuzin. Two 75% dry flow able and two 42% liquid flowable formulations were analyzed by 18 laboratories. Formulations were extracted by shaking or ultrasonic mixing for 1-5 min with methylene chloride which contained di-n-butyl phthalate as an internal standard. The extracts were injected into a gas chromatograph equipped with an OV-225 column. Peak area ratios and peak height ratios showed no significant difference. The reproducibility coefficient of variation was 0.75% for the 75% formulation and 1.41% for the 42% formulation. This GC method has been adopted official first action.

Liquid Chromatographic Determination of Propoxur in Technical and Formulated Products: Collaborative Study

A liquid chromatographic method for the determination of propoxur in technical and formulated products has been subjected to a collaborative study with 8 participating collaborators. Formulations are extracted with acetonitrile and analyzed by reverse phase chromatography, with n-butyrophenone as an internal standard. Collaborators were furnished with samples of technical, 70% wettable powder, 1.5 emulsifiable, and 2% bait. Coefficient of variation values obtained on the 4 samples were 0.34, 0.68, 3.25, and 5.41%, respectively. The method has been adopted official first action.

Atomic Absorption Spectrophotometric Determination of Chelated Iron in Iron Chelate Concentrates: Collaborative Study

An atomic absorption Spectrophotometric (AAS) method for determining chelated iron in iron chelate concentrates was collaboratively studied by 13 laboratories. Nonchelated iron was selectively precipitated as ferric hydroxide from an aqueous solution of the sample by adjusting to pH 8.5 with sodium hydroxide. A filtered portion of the sample solution was diluted with 0.5N HC1, and the iron was determined by AAS using standards containing disodium EDTA. Six pairs of iron chelate materials (12 samples) were analyzed and the average coefficients of variation were iron EDTA 3.52%, iron HEDTA 4.16%, iron DTPA 3.55%, iron EDDHA 3.52%, iron citrate 2.86%, and iron DPS 8.47%. The method has been adopted official first action.

High Performance Liquid Chromatographic Analysis of Rotenone Formulations: Collaborative Study

A collaborative study was conducted on a high performance liquid chromatographic (HPLC) method for determining rotenone in formulations. One liquid and 4 dust samples, containing other rotenoids and pesticides, with rotenone guarantees ranging from 0.75% to 20% were analyzed by 16 laboratories. Peak height measurements were used by 14 laboratories while 8 laboratories used integrator area measurements. Samples were extracted on a rotary shaker for 1% h with dioxane. An aliquot was analyzed using reverse phase HPLC and UV detection at 280 nm. Coefficients of variation ranged from 2.47 to 3.19% for peak height determinations and from 2.56 to 6.00% for peak area determinations. One collaborator analyzed the samples by the official infrared method for a comparison. The HPLC method has been adopted official first action.

Jimson weed seed toxicity in cattle

A subacute experiment was undertaken for 14 days. The results obtained from these studies suggest that: 1) unless a highly Jimson weed seed contaminated feed is ingested (greater than 0.09% of body weight) or force fed, death should be a rare consequence of Jimson weed seed contamination; 2) Jimson weed seed toxicity in cattle as a result of feed contamination appears a self-limiting problem (rumen atony and anorexia prevent further intoxication until the blood levels of alkaloids are reduced to allow normal ruminant intestinal function); 3) cattle may exhibit signs of atropine toxicity at contamination levels of 881 seed/kg of feed or higher; 4) rumen fluid from heifers fed diet containing 4,408 Jimson weed seed had the greatest VFA concentration change from day 0 to 7; 5) in vitro fermentation of diets resulted in no difference in IVDMD values, but VFA concentration values tended to increase with increased concentrations of Jimson weed seed in the diet.

Gas-Liquid Chromatographic Method for the Analysis of Microencapsulated Diazinon Insecticide: Collaborative Study

The determination of diazinon insecticide in Knox Out 2FM formulation was studied collaboratively by 18 laboratories. Knox Out 2FM is a flowable microencapsulated insecticide formulation containing 23 wt% active ingredient. Analytical samples are first treated by grinding in a tissue grinder and then extracted in situ with acetonitrile. This preparative step breaks the capsules and allows the active ingredient to dissolve in the solvent. Single determinations on each of 2 closely matched samples were made by flame ionization gas-liquid chromatography. The standard deviation by analysts was 0.18 wt% and the coefficient of variation was 0.76%. The combined laboratory and analyst variation gave a standard deviation of 0.59 wt% and a coefficient of variation of 2.49%. The method has been adopted official first action.

Minicolumn Detection Methods for Aflatoxin in Raw Peanuts: Collaborative Study

The Holaday-Velasco method and a modified Holaday method have been compared. The former method combines the speed and simplicity of the Holaday extraction and cleanup with the sensitivity of the minicolumn originally described by Velasco. The combination method has been approved by the AOAC and the AACC for determining aflatoxin in corn. The Holaday method was modified by substituting toluene for benzene in the solvent partition, and methylene chloride for chloroform in the minicolumn development to eliminate use of hazardous solvents. The neutral alumina in the Holaday minicolumn was changed from activity V to activity III to provide a more stable column. At aflatoxin levels in raw peanuts of 13-20 ng/g, the presence of aflatoxin was missed by the modified Holaday method in 4 analyses (3 laboratories) of 42 reported. There were no misses in this contamination range by the Holaday-Velasco method. There were no misses by either method with samples containing >20 ng total anatoxins/g. Analysis of uncontaminated raw peanuts by the modified Holaday method resulted in 2 false positives of 14 reports; the Holaday-Velasco method produced no false positive reports from 15 analyses of uncontaminated peanuts. The Holaday-Velasco method was adopted official first action for peanuts.

Minicolumn detection methods for aflatoxin in raw peanuts: collaborative study

The Holaday-Velasco method and a modified Holaday method have been compared. The former method combines the speed and simplicity of the Holaday extraction and cleanup with the sensitivity of the minicolumn originally described by Velasco. The combination method has been approved by the AOAC and the AACC for determining aflatoxin in corn. The Holaday method was modified by substituting toluene for benzene in the solvent partition, and methylene chloride for chloroform in the minicolumn development to eliminate use of hazardous solvents. The neutral alumina in the Holaday minicolumn was changed from activity V to activity III to provide a more stable column. At aflatoxin levels in raw peanuts of 13-20 ng/g, the presence of aflatoxin was missed by the modified Holaday method in 4 analyses (3 laboratories) of 42 reported. There were no misses in this contamination range by the Holaday-Velasco method. There were no misses by either method with samples containing greater than 20 ng total aflatoxins/g. Analysis of uncontaminated raw peanuts by the modified Holaday method resulted in 2 false positives of 14 reports; the Holaday-Velasco method produced no false positive reports from 15 analyses of uncontaminated peanuts. The Holaday-Velasco method was adopted official first action for peanuts.

Gas-Liquid Chromatographic Method for Determining Bolstar Insecticide in Formulations: Collaborative Study

A gas-liquid chromatographic (GLC) method for determining Bolstar insecticide in liquid technical material and emulsifiable concentrate formulations was collaboratively studied using Youden’s matched pair scheme. Three matched sample pairs were analyzed by 21 laboratories using integrator area measurements and/or peak height measurements. Samples of a technical material containing about 78% active ingredient, a commercial 6 lb/ gal. emulsifiable concentrate containing about 64% active ingredient, and a synthetic emulsifiable concentrate containing about 64% active ingredient were dissolved in a measured amount of internal standard solution, tetracosane in toluene, and were subjected to gas-liquid chromatography on a column of 1.5% SE-30 + 1.5% OV-210. Bolstar was detected using flame ionization. The mean coefficient of variation by integrator area measurement for the 6 samples was 1.22%, and the mean coefficient of variation by peak height measurement for the 6 samples was 1.65%. The method was adopted as official first action.

Gas-Liquid Chromatographic Determination of N-Octylbicycloheptene Dicarboximide: Collaborative Study

A gas-liquid chromatographic method for the quantitative determination of N-octylbicycloheptene dicarboximide (MGK® 264 Synergist) was collaboratively studied with technical material and 2 formulations. The samples are diluted with acetone and determined after gas chromatography on an OV-1 column by a flame ionization detector. A statistical evaluation of the matched pair technical samples indicates good agreement among collaborators. An evaluation of the F-factor did not indicate significant systematic error contributions. A statistical evaluation of results for the 2 formulations showed coefficients of variation of 1.25 and 0.97. An examination of the t-values showed no contribution to systematic error. The method has been adopted as official first action.

Infrared Spectrophotometric Method for Analysis of Guthion Insecticide: Collaborative Study

A collaborative study on the assay of Guthion (azinphos methyl) has been conducted by 10 laboratories. Data were obtained on a 2 Ib/gal. liquid concentrate and a 50% wettable powder formulation. The procedure specifies extraction and/or dilution followed by infrared absorbance measurement at 654 cm-1. The method has been adopted as official first action.

Aluminum oxide cleanup of feed grade fats for residues of dieldrin

A method is described for the analysis of dieldrin in feed grade fats. Fat samples in petroleum ether are cleaned up by column chromatography on 10% deactivated aluminum oxide followed by Florisil and analyzed by electron capture gas chromatography. Fourteen laboratories tested the method for determining dieldrin in naturally contaminated feed grade fats. Recoveries averaged greater than 90% with a coefficient of variation of 13% (0.54 ppm +/- 0.07), indicating that the method is sufficiently reproducible to be used by different laboratories for detecting dieldrin in feed grade fats.

Constituents of the cotton bud: XII. The carotenoids in buds, seeds and other tissue

Eleven carotenoid pigments were found in the bud, leaf, flower petal, seedling and seed of the cotton plant; nine were identified and quantitated. The most abundant carotenoids in the green tissue of the cotton plant were beta-carotene and lutein. Carotene hydrocarbons comprised 12% of the total carotenoids in the seed, 15% in the 1-day-old flower petal, 51% in the bud and 57% in green leaves. Only 5,8-epoxy carotenoids were found in the flower petals and only 5,6-epoxides in the other tissue but both were present in the seed. The colorless phytoene precursors to the carotenoids comprised from 20% to 38% of the total carotenoid pigment in the growing tissue of the plant.

Pesticide Residues in Commercial Animal Feeds

One hundred and one commercial feeds, of which 87 were dairy feeds or supplements, were analyzed for chlorinated organic pesticide residues by gas chromatography utilizing 5% SE-30 for the stationary phase and electron capture detection. A computation scheme for determining γ-BHC, aldrin, dieldrin, endrin, DDD, DDT, methoxychlor, heptachlor, heptachlor epoxide, chlordane, and toxaphene in combination with each other was developed, and values were tabulated for each in each feed. Contaminations ranged from low tens to hundreds (ppb). Most of the feeds contained residue amounts below those which would be expected to produce detectable residues in milk. Higher contamination levels were tentatively correlated with specific feed ingredients, as well as with protein and crude fiber content. Higher contaminations were observed with higher fiber content, lower feed protein value, and when grain screenings, rice bran, or rice mill by-product were ingredients. Much lower contaminations were associated with ground milo, wheat bran and middlings, ground and crimped oats, linseed oil meal, and various corn products.