Showing papers in "Journal of AOAC International in 1975"
458 citations
222 citations
TL;DR: AOAC fluorometric method for selenium in plants, 3.074-3.078, has been modified to simplify the method and to make it more accurate as mentioned in this paper.
Abstract: The official first action AOAC fluorometric method for selenium in plants, 3.074-3.078, has been modified to simplify the method and to make it more accurate. The digestion time has been increased from 15 to 30 min past the appearance of perchloric acid fumes to better assure complete oxidation of all forms of selenium to selenite. Preparation of the 2,3-diaminonaphthalene solution, the reagent used for fluorometric analysis, has been changed so that the reagent is stable for several weeks; in the previous writeup, this solution had to be prepared daily. Special equipment (micro-Kjeldahl flasks with ground glass joints) has been eliminated and cyclohexane has been substituted for decahydronaphthalene. The modified method is convenient and applicable to a wide range of materials; it yields results comparable to those from the official method.
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TL;DR: The chemical method for confirmation of the identity of aflatoxin by derivative formation directly on the TLC plate was studied collaboratively by 8 participants and has been adopted as official first action.
Abstract: The chemical method for confirmation of the identity of aflatoxin by derivative formation directly on the TLC plate was studied collaboratively by 8 participants. The results show that aflatoxin B-1 was confirmed in 17 of 17 sample extracts representing 15 mu-g aflatoxin B-1/kg peanut butter, in 13 of 16 extracts representing 5 mu-g/kg, and in none of the 7 aflatoxin-free extracts. Collaborators commented that the method was easily performed and gave good results. The method has been adopted as official first action.
61 citations
TL;DR: A rapid screening procedure has been developed for these mycotoxins using this methanol-water extraction system as a base and it is found that the aflatoxins and zearalenone are detected by half-plate TLC.
Abstract: The methanol-water extraction system used in AOAC Method II for aflatoxins extracts both the aflatoxins and zearalenone from corn. Using this methanol-water extraction system as a base, a rapid screening procedure has been developed for these mycotoxins. The methanol-water extract is defatted with hexane and the pigments are precipitated with copper carbonate. The aflatoxins and zearalenone are subsequently extracted into chloroform and are then detected by half-plate TLC. An elapsed time of about 1 hr is required to analyze 1 sample. The sensitivity of the method is about 2 mu-g/kg for aflatoxin B-1 and 100 mu-g/kg for zearalenone.
57 citations
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TL;DR: Nine laboratories participated in a collaborative study of the determination of total cholesterol in deviled ham sandwich spread, vegetable beef stew, corned beef hash, frozen chicken pot pie, pizza pepperoni, fish sticks, breaded shrimp, chocolate-covered candy bars, dried whole egg solids, and nonfat dry milk and the results are reported here.
Abstract: A method is described for the determination of total cholesterol in multicomponent foods and also other products such as nonfat dry milk, dried whole egg solids, and certain candy bars. The lipid is extracted from the sample by a mixed solvent and saponified. The unsaponifiable fraction which contains the cholesterol and other sterols is extracted with benzene. An aliquot is evaporated to dryness and the residue is dissolved in dimethylformamide. The sterols are derivatized to form trimethylsilyl (TMS) ethers. The TMS-cholesterol derivative is quantitatively determined by gas-liquid chromatography, using 5alpha-cholestane as an internal standard. Nine laboratories participated in a collaborative study of the determination of total cholesterol in deviled ham sandwich spread, vegetable beef stew, corned beef hash, frozen chicken pot pie, pizza pepperoni, fish sticks, breaded shrimp, chocolate-covered candy bars, dried whole egg solids, and nonfat dry milk and the results are reported here. The coefficient of variation ranged from 5.64 to 23.2%, with an average coefficient of variation of 14.8%.
14 citations
TL;DR: The official final action acid hydrolysis method, 14.019, for the determination of fat in foods was successfully applied, with slight modifications, to the analysis of homogenates of food, feces, and animal tissues as well as dry samples of mixed foods.
TL;DR: A published procedure using Amberlite LA-2 (a liquid anion exchange resin) solutions to extract colors from food and the salt solution cellulose chromatographic technique to separate colors from each other were updated and submitted to collaborative study.
Abstract: A published procedure using Amberlite LA-2 (a liquid anion exchange resin) solutions to extract colors from food and the salt solution cellulose chromatographic technique to separate colors from each other were updated and submitted to collaborative study. Three batches of cookies and 4 purchased products were analyzed by 13 collaborators. The 3 batches of cookies contained different color mixtures requiring the selection of various procedures. The 4 purchased products were selected principally to include a variety of foods. Some results were partially deficient. The deficiencies reflect certain inadequacies in the directions as written rather than basic flaws in the method. Some improvements were suggested by the collaborators. The Assocaite Referee recommends that the method be further revised to correct the present inadequacies and to include some improvements, and that the revised method be submitted to another collaborative study.
TL;DR: A collaborative test was performed to evaluate a new potentiometric method for the analysis of fluoride in vegetation as discussed by the authors, which was designed to provide estimates of accuracy and within and between-laboratory precision of a method that employs extraction of fluoride, followed by analysis with an ion selective electrode.
Abstract: A collaborative test was performed to evaluate a new potentiometric method for the analysis of fluoride in vegetation. The study was designed to provide estimates of accuracy and within- and between-laboratory precision of a method that employs extraction of fluoride, followed by analysis with an ion selective electrode. A group of laboratories experienced in fluoride analysis was provided with representative aliquots of specially prepared samples of vegetation and a detailed set of instructions. Reference values were established for the fluoride concentrations of vegetation samples prior to their distribution. Nine of the 23 laboratories participating in the study adhered strictly to instructions so the results from these 9 participants were used to evaluate the method. The coefficient of correlation between results from selected laboratories and reference values was 0.999. Deviations from reference values averaged 5.4% and relative standard deviations ranged from about 20% at 24 ppM to about 10% for concentrations > 100 ppM fluoride. On the basis of these results, the new method has been adopted as official first action. The method is simpler and faster; it requires less equipment than the current official final action method (25.029-29.035) and can be used to estimate fluoride concentration in the foliage ofmore » plants exposed to fluorides in the atmosphere or in soils provided samples contain > 10 ppM fluoride. Separate studies indicate, however, that certain samples of vegetation may be refractory to analysis by this potentiometric method. 16 references, 4 tables.« less
TL;DR: The procedure was successfully applied to samples of Lake Michigan chubs containing residues of PCB's and theDDT group and to extracts of human serum fortified with Aroclors and the DDT group, where recoveries generally were poorer with A roclors of lower chlorine content and decreased with decreasing quantity of AroClor present.
Abstract: A micro scale procedure is described for quantitatively separating polychlorinated biphenyls (PCBs) from DDT and its analogs. DDT and TDE are initially dehydrochlorinated with ethanolic KOH to their respective olefins, DDE and TDE-olefin (1-chloro-2,2-bis (p-chlorophenyl) ethylene). The olefins are than oxidized by CrO3 in acetic acid to the more polar dichlorobenzophenone. PCB's are eluted from a micro Florisil column with petroleum ether. Typical recoveries in the ppm range (based on a 5 g sample) were is greater than 80% for Aroclors 1254 and 1260. Recoveries generally were poorer with Aroclors of lower chlorine content and decreased with decreasing quantity of Aroclor present. The DDT group was not quantitatively determined; recoveries averaged is greater than 60% for the DDT group in the ppm range (based on a 5 g sample). The procedure was successfully applied to samples of Lake Michigan chubs containing residues of PCB's and the DDT group and to extracts of human serum fortified with Aroclors and the DDT group.
TL;DR: This procedure can be used to detect the total nitrofuran content of as little as 10 ppb muscle tissues and milk, 100 ppb liver, and 50 ppb fat with no interference from related veterinary nitrodrugs.
Abstract: A method was developed for measuring low levels of total nitrofurans in animal tissues and milk. The antimicrobial nitrofurans (5 or more products) used in agriculture are extracted from tissue with aqueous acid in the presence of ethyl acetate. After centrifugation and evaporation, the organic residue is washed with hexane and the nitrofurans are hydrolyzed to 5-nitrofuraldehyde in aqueous acid at 70 degrees C. The hydrolysis product is extracted with benzene and measured by gas-liquid chromatography with electron capture detection. Recoveries of nitrofurazone and furazolidone from fortified poultry and swine tissues at the levels of 0.5 and 0.1 ppm are 75 and 65%, respectively. This procedure can be used to detect the total nitrofuran content of as little as 10 ppb muscle tissues and milk, 100 ppb liver, and 50 ppb fat with no interference from related veterinary nitrodrugs.
TL;DR: In this paper, a simple and fast procedure was proposed to determine monosodium glutamate in food products using a short ion exchange column and subsequently determined fluorometrically with fluorescamine.
Abstract: In a simple and fast procedure, monosodium glutamate in food products is first separated by a short ion exchange column and subsequently determined fluorometrically with fluorescamine. An average recovery of 90.8% with a standard deviation of plus or minus 6.67% was obtained for added monosodium glutamate in a series of 8 products. As little as 0.05% monosodium glutamate can be determined. The method is faster than the official method and saves 5 hr/determination.
TL;DR: This method has potential as a preparative separation technique for rotenoids and quantitatively measure rotenone in pesticide formulations and is rapid (rotenone is eluted in 12 min) and reproducible.
Abstract: The rotenoids deguelin, B-dihydrorotenone, dehydrorotenone, rotenone, 6alpha beta, 12alpha beta-rotenolone, and tephrosin were chromatographed on 8-12 mum silica. A mobile phase of chloroform-isooctane (35+65) pumped at a flow rate of 1 ml/min through a 30 cm column was used and the absorbance of the eluate was monitored at 294 nm. Rotenone, B-dihydrorotenone, deguelin, and dehydrorotenone are completely resolved while 6alpha beta, 12alpha beta-rotenolone and tephrosin chromatograph as one peak. This method has potential as a preparative separation technique for rotenoids. Also described is a procedure to quantitatively measure rotenone in pesticide formulations. Samples were extracted with chloroform and chromatographed at a flow of 2.5 ml/min. The method is rapid (rotenone is eluted in 12 min) and reproducible.
TL;DR: A gas-liquid chromatographic (GLC) method was developed for the determination of residues of resmethrin in corn, cornmeal, flour, and wheat and compared with known standards that had undergone the same cleanup procedures.
Abstract: A gas-liquid chromatographic (GLC) method was developed for the determination of residues of resmethrin ((5-benzyl-3-furyl)methyl cis-trans-(+/-)-2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylate) in corn, cornmeal, flour, and wheat. The commodity, fortified with resmethrin, was extracted by tumbling with pentane and transferred to acetonitrile, the fat was partitioned off, and the sample was chromatographed with 3% ethyl acetate in pentane on Florisil containing 0.5% water. The resmethrin residue was determined by GLC with a flame ionization detector. The results were compared with known standards that had undergone the same cleanup procedures. The method was sensitive to concentrations of resmethrin to 0.2 ppm, recoveries averaged 83%, and reproducibility was good.
TL;DR: To remove a number of possible interferences the hydrolyzed phenols are steam-distilled and treated with 1-fluoro-2,4-dinitrobenzene and/or 4-chloro-alpha, alpha,alpha-trifluoro-3,5-d Initrotoluene to form the ether derivatives, which enable the carbamate pesticides to be detected in vegetables and fruits at the 0.05 ppm level.
Abstract: Carbamate pesticide residues are extracted from vegetables and fruits with methylene chloride. The extracts are spotted on silica gel plates and the pesticides are detected by an enzymatic inhibition technique. For quantitative determination, aliquots of the methylene chloride extracts are evaporated to dryness in a rotary evaporator. After the residues are dissolved in ethanol, 0.5N NaOH is added in the hydrolysis step. To remove a number of possible interferences the hydrolyzed phenols are steam-distilled and treated with 1-fluoro-2,4-dinitrobenzene and/or 4-chloro-alpha,alpha,alpha-trifluoro-3,5-dinitrotoluene to form the ether derivatives. Efficiency in the conversion of the phenolic moieties to the phenyl ethers is about 100%. The resulting electron-capturing derivatives enable the carbamate pesticides to be detected in vegetables and fruits at the 0.05 ppm level. Recoveries of 90-94% were obtained from vegetables and fruits fortified with 0.5-2.0 ppm carbaryl, Mesurol, and propoxur.