Showing papers in "Journal of AOAC International in 1978"

Reverse phase high pressure liquid chromatographic determination of aflatoxins in foods.

Abstract: A method for determining aflatoxins by high pressure liquid chromatography (HPLC) with fluorescence detection after CB extraction and cleanup has been applied to various foods. Recoveries at 1--15 ppb levels from green coffee and peanut butter was 72--85 and 74--104%, respectively. Precision of the method has been tested for peanut butter. Other products to which the method has been successfully applied include tree nuts, seeds, grains, chocolate-covered peanut butter candy, and roasted, salted-in-shell peanuts. High levels of aflatoxins found in several samples of nuts by this method have been verified by the official thin layer chromatographic (TLC) method. The advantages of this HPLC method are speed, precision, sensitivity, selectivity, and immediate chemical confirmation of aflatoxins B1 and G1. None of the products analyzed required special cleanup procedures. Preparative-scale HPLC was used to isolate purified B1 for toxicity testing.

Determination of zearalenone in cornflakes and other corn-based foods by thin layer chromatography, high pressure liquid chromatography, and gas-liquid chromatography/high resolution mass spectrometry.

Abstract: A simple cleanup procedure based on pH adjustments was used to obtain extracts of corn foods. The method gave good recoveries of zearalenone determined by thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC). As little as 5 ng zearalenone was detected by TLC, using Fast Violet B Salt as the spray reagent; the lower limit of detection in cornflakes was about 20 microgram/kg. With HPLC on Spherisorb silica (5 micrometer) and detection by fluorescence at an excitation maximum of 310 nm as little as 5 microgram zearalenone/kg cornflakes could be determined. While the TLC method was also applicable to corn chips, cornmeal, popcorn, and frozen corn, an interference was observed in HPLC of the latter 3 products. This interference was separated from zearalenone by adding a second HPLC analytical column (Spherisorb ODS). Gas-liquid chromatography coupled with mass spectrometric single ion monitoring at high resolution, although of limited availability, was shown to be the most sensitive and selective method for determining zearalenone in corn foods. The natural occurrence of zearalenone in a sample of cornflakes (13-20 microgram/kg) was demonstrated by all 3 detection procedures.

Gas-liquid chromatographic determination of T-2 toxin and diacetoxyscirpenol in corn and mixed feeds.

Abstract: A gas-liquid chromatographic method has been developed for the simultaneous determination of the T-2 toxin and diacetoxyscirpenol (DAS) in corn and mixed feeds. The analytes are extracted with aqueous methanol. Ammonium sulfate is used to denature and precipitate proteinaceous compounds and to salt out low polar compounds. The analytes are selectively concentrated into chloroform, which is washed with aqueous potassium hydroxide to remove acidic compounds. Residual interferences are removed by silica gel column chromatography. Heptafluorobutrylimidazole (HFBI) is added to form esters of the analytes. The HFB-esters are separated on an SE-30 glass column and measured witha 63Ni electron capture detector, using methoxychlor as an internal standard. The method has been applied to corn, livestock feeds, and pet food. The limit of detection is 100 ng T-2 toxin and 25 ng DAS/G. Average recoveries of 105 and 97% and coefficients of variation of 17 and 10% were obtained for T-2 toxin and DAS, respectively.

Trenbolone acetate: experiences with bound residues in cattle tissues.

Abstract: Two heifers were implanted with 300 mg of the radiolabeled anabolic steroid, trenbolone acetate (TBA). After a 60 day slaughter and a 60 day removal followed by 76 day slaughter, total 3H-content in various tissues was 0.5--25 ng/g equivalents of TBA. Radioimmunoassay of the tissues showed that only 1--5% of the total residue present was TBA, its main metabolite trenbolone (TBOH), and TBOH glucuronide, plus up to 5% of other organic-soluble material. Of the radioactivity remaining about half was directly water-soluble, and the insoluble residue could be made water-soluble by treatment with the proteolytic enzymes pepsin and trypsin. These 2 portions were purified with Sephadex G-25 to give a low and high molecular weight fraction. Raney nickel reduction of sulfur bonds in either fraction released up to 50% of radioactivity into the organic phase. TLC showed that the latter contained 2 components which had characteristics similar to TBOH and its metabolites, and thus were at least partly drug-related metabolites. In vitro experiments with bovine liver also showed a small but definite protein binding. It is proposed that in dealing with these covalently bound residues, priority be given to the reactive drug intermediate and the type of binding to macromolecules rather than to the presence of the bound residue itself.

Aflatoxin Formation on Sixteen Soybean Varieties

Abstract: 16 commercial var. of soybeans were each inoculated separately with 5 isolates of fungi from the Aspergillus flavus series to determine varietal differences in supporting aflatoxin production. The isolates were 2 strains of A. parasiticus (NRRL 2999 and NRRL 3145), 2 strains of A. flavus (NRRL 3357 and NRRL 3353), and 1 strain from a new variant of A. flavus (NRRL 3251). Levels of aflatoxin formed were dependent both on the isolate and on the var. of soybeans. Amsoy-71, Calland, Harosoy, and Pamona var. were the poorest substrates for aflatoxin production in the laboratory fermentation, so they may be resistant to mould invasion and/or toxin formation.

High pressure liquid chromatographic determination of aflatoxins in peanut products.

Abstract: A precise and sensitive high pressure liquid chromatographic method is proposed for determining aflatoxins B1, B2, G1, and G2 in all types of peanut products. The method is based on acidified aqueous methanol extraction, partition of aflatoxins into dichloromethane, and purification of the extract on a 2 g silica gel column. Aflatoxins in the purified extract are completely resolved on a microparticulate (10 micron) porous silica gel column in approximately 10 min with a water-saturated chloroform-cyclohexane-acetonitrile solvent. The preferred detection system, B1, and B2 by ultraviolet absorbance at 360-365 nm and G1 and G2 by fluorescence, allows accurate and sensitive detection of all 4 aflatoxins at levels as low as 0.3-1.0 microgram/kg. Repetitive assay of 3 samples of naturally contaminated peanut butters containing total aflatoxins (B1 + B2 + G1 + G2) at levels of 5, 10, and 15 microgram/kg gave within-laboratory coefficients of variation of 11, 5, and 5% respectively.

Simplified fat extraction with sulfuric acid as cleanup procedure for residue determination of chlorinated hydrocarbons in butter.

Abstract: A new cleanup procedure is described for chlorinated hydrocarbon residues in butterfat. The method is based on the dropwise addition of H2SO4 to a fat solution column and continuous removal of the lipids and the acid. The cleanup of 0.25-2.0 g fat requires only 10-40 ml sulfuric acid and 12-17 ml petroleum ether. There is no need for any further cleanup step, solvent evaporation, or centrifugation. The method is easy to standardize and is suitable for automation. At least 30 fat samples can be cleaned up manually by one analyst in one day. Recoveries were complete (greater than 90%) for polychlorinated biphenyl compounds and for 13 chlorinated pesticides of 16 examined. The method was tested on chlorinated hydrocarbon residues in commercial butter and the results were compared with those obtained with the acetonitrile method. The versatility and limitations of the method were investigated by varying the sulfuric acid strength, initial fat solution concentration, and column dimensions.

Application of the official AOAC chloresterol Method to a wide variety of food products.

Abstract: This paper presents analytical data on the cholesterol content of selected consumer food products including some fats and oils. The cholesterol data are grouped by food products. To determine the reproducibility of cholesterol values, recovery data were obtained from samples of pure vegetable shortening spiked at 40 and 20 mg cholesterol (as cholesteryl palmitate)/100 g fat. Average recoveries were 97.1% and 95.5% with coefficients of variation of 1.27 and 3.24%, respectively.

High pressure liquid chromatographic determination of xanthomegnin in corn.

Abstract: A method is described for the detection and quantitative analysis of xanthomegnin in corn samples. Initial extraction with CHCl3 in the presence of 0.5M H3PO4 is followed by additional purification using silica gel column chromatography. A high pressure liquid chromatograph equipped with a microparticle silica gel column and a 405 nm absorbance detector is used for detection and quantitation of the xanthomegnin. The identity of xanthomegnin is confirmed by thin layer chromatography on silica gel plates developed with benzene-methanol-acetic acid (90 + 5 + 5). The recovery of xanthomegnin added to corn samples at levels of 0.75--9.6 mg/kg averaged 41% with a coefficient of variation of 25%.

Antibiotic residues: regulations, tolerances, and detection in the European Economic Community.

Abstract: The use of antimicrobial agents for growth promotion and therapy in the European Economic Community and the resulting public health problems are discussed. Methods for detection of residues based on microbiological criteria for acceptance are presented and evaluated.

Trends in Levels of N-Nitrosopyrrolidine in Fried Bacon

Abstract: Commercially purchased bacon has been periodically analyzed since 1971 for N-nitrosopyrrolidine in the fried product. The downward trend in the concentration of N-nitrosopyrrolidine that has been observed is partially explained by the use of reduced levels of nitrite and increased levels of ascorbate in bacon curing mixtures.

Method for maintaining viability of Clostridium perfringens in foods during shipment and storage: collaborative study.

Abstract: A collaborative study was conducted in 12 laboratories to determine the effectiveness of a new method for maintaining vegetative cells of Clostridium perfringens in viable condition during storage and transport of food specimens to the laboratory. The collaborative results showed that treatment of brown gravy and roast beef samples with an equal amount by weight of sterile buffered glycerol-sodium chloride solution to give a final 10% glycerol concentration and storage with Dry Ice for 10 days at -56 degrees C resulted in plate counts of C. perfringens which were 2-4 log cycles higher with 2 different strains than counts with untreated specimens stored by the usual method at -20 degrees C. Plate counts obtained with the treated specimens stored with Dry Ice were less than 1 log cycle lower than counts made with identical specimens before freezing for storage and shipment to the collaborators. The results with treated specimens were also more uniform among the different laboratories. Because the new method for storage and shipment of food samples was so effective for maintaining viability of the organism, the official first action method for C. perfringens (46.B01) was changed to incorporate these procedures as part of the method.