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1.
A collaborative study of a liquid chromatographic method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, Canada, South Africa, and Switzerland. Twenty-one artificially contaminated raw peanuts, peanut butter, and corn samples containing varying amounts of aflatoxins B1, B2, G1, and G2 were distributed to participating laboratories. The test portion was extracted with methanol-0.1N HCl (4 + 1), filtered, defatted with hexane, and then partitioned with methylene chloride. The concentrated extract was passed through a silica gel column. Aflatoxins B1 and G1 were derivatized with trifluoroacetic acid, and the individual aflatoxins were determined by reverse-phase liquid chromatography with fluorescence detection. Statistical analysis of the data was performed to determine or confirm outliers, and to compute repeatability and reproducibility of the method. For corn, relative standard deviations for repeatability (RSDr) for aflatoxin B1 ranged from 27.2 to 8.3% for contamination levels from 5 through 50 ng/g. For raw peanuts and peanut butter, RSDr values for aflatoxin B1 were 35.0 to 41.2% and 11.2 to 19.1%, respectively, for contamination levels from 5 through 25 ng/g. RSDr values for aflatoxins B2, G1, and G2 were similar. Relative standard deviations for reproducibility (RSDr) for aflatoxin B1 ranged from 15.8 to 38.4%, 24.4 to 33.4%, and 43.9 to 54.0% for corn, peanut butter, and raw peanuts, respectively. The method has been adopted official first action for the determination of aflatoxins B1, B2, G1, and G2 in peanut butter and corn at concentrations greater than or equal to 13 ng total aflatoxins/g.  相似文献   

2.
Three different methods were compared for the determination of total flatoxins in corn and peanuts naturally contaminated with aflatoxins and in corn, peanuts, cottonseed, peanut butter, and poultry feed spiked with aflatoxins B1, B2, and G1. The 3 methods were an enzyme-linked immunosorbent assay (ELISA) screening test; a monoclonal antibody-affinity column-solid-phase separation method; and the AOAC official thin-layer chromatography (TLC) methods for all except poultry feed, for which Shannon's TLC method for mixed feed was used. The ELISA test is designed to provide only positive results for total aflatoxins at greater than or equal to 20 ng/g or negative results at less than 20 ng/g. The affinity column separation is coupled with either bromination solution fluorometry to estimate total aflatoxins or liquid chromatography (LC) to quantitate individual aflatoxins. Fluorodensitometry was used to determine aflatoxins in commodities analyzed by the TLC methods. The LC and TLC results were in good agreement for all the analyses. The results for the affinity column using bromination solution fluorometry were similar except those for cottonseed, which were about 60% higher. The ELISA screening method correctly identified naturally contaminated corn and peanut positive samples. No false positives were found for controls. The correct response for spiked corn, raw peanuts, peanut butter, and cottonseed at greater than or equal to 20 ng aflatoxins/g was about 90%. The correct response for spiked poultry feed at greater than or equal to 20 ng aflatoxins/g was about 50%.  相似文献   

3.
A screening method for aflatoxins was collaboratively tested on 11 different agricultural and food products: white and yellow corn, peanuts, peanut butter, pistachio nuts, peanut meal, cottonseed meal, chicken, pig, and turkey starter rations, and dairy cattle feed. The method involves a rapid extraction and cleanup procedure followed by the detection of total aflatoxins (B1 + B2 + G1 + G2) as a fluorescent band on the Florisil layer of a Velasco-type minicolumn. The results of 32 collaborators from 10 different countries are presented. Samples containing 0, 5, 10, 15, 20, and 25 mug aflatoxins/kg were analyzed. Eighty-four per cent of the negative samples and 89% of the samples containing 10-25 mug total aflatoxins/kg were correctly identified. This method has been adopted as official first action for the detection of aflatoxins in corn, peanuts, peanut butter, peanut meal, cottonseed meal, mixed feeds, and pistachio nuts.  相似文献   

4.
An improved enzyme-linked immunosorbent assay (ELISA) for aflatoxin B1 in cornmeal and peanut butter was developed. Aflatoxin B1 in cornmeal and peanut butter samples was extracted with 70% methanol in water containing 1% dimethylformamide diluted with assay buffer to a final concentration of 7.0% methanol, and directly subjected to an ELISA procedure that took less than 1 h for quantitative analysis and less than 30 min for screening tests. Analytical recoveries for 5-100 ppb B1 added to the cornmeal and peanut butter were 91 and 95.4%, respectively. The interwell and interassay coefficient of variation was 10% or less at the 20 ppb level and above. Agreement for B1 levels in more than 30 naturally contaminated corn, mixed feed, and peanut butter samples was excellent between the ELISA data and the data obtained from different independent laboratories using TLC or other analytical methods.  相似文献   

5.
A method is described for rapid cleanup followed by reverse-phase liquid chromatographic (LC) quantitation of aflatoxins in raw peanuts. A modified minicolumn cleanup is used for sample preparation, and a preliminary estimation of aflatoxin content by minicolumn can be made so that highly contaminated samples can be diluted before LC analysis. The use of the simple, quick minicolumn cleanup eliminates the need for further column or cartridge cleanup, thus greatly reducing sample preparation time. Sensitive quantitation is achieved using a phenyl column, a mobile phase of water-tetrahydrofuran (80 + 20, v/v), and postcolumn derivatization with water-saturated iodine followed by fluorescence detection. The recoveries of aflatoxins B1, B2, G1, and G2 from peanut meal spiked at 3 levels ranged from 71.7 to 88.3% (average 80%) with coefficients of variation from 2.7 to 10.4%.  相似文献   

6.
A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, South Africa, Switzerland, The Netherlands, Tunisia, and the United States. Twenty-eight samples of raw and roasted peanuts, corn, whole cottonseed, cottonseed meal, ammoniated cottonseed meal, and poultry feed containing various quantities of natural aflatoxins and supplemented when appropriate with aflatoxin B1 were distributed to participating laboratories for testing. The assay is based on conjugation of pure aflatoxin B1 to an enzyme and the competition between this conjugate and (free) aflatoxins in the product for aflatoxin-specific antibodies coated onto microtiter well walls. After a wash step to remove all unbound aflatoxins, a substrate, added to each well, is catalyzed from a colorless to a green solution by any bound enzyme-conjugated aflatoxin B1 present. The intensity of the color decreases as the amount of free aflatoxin B1 in the product increases. Overall correlation was good between ELISA and thin-layer chromatographic (TLC) results for cottonseed products and mixed feed. Variable results were reported for corn and peanut product samples. Although some positive samples (greater than 15 ng/g) of cottonseed products and mixed feed were reported to contain less than 15 ng/g by visual determination, a review of data for absorbance measurements showed that the contamination level was close to the greater than or equal to 15 ng/g standard and would not have been reported as negative under routine screening.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

7.
A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, The Netherlands, Switzerland, Tunisia, and the United States. Twelve raw and roasted peanut and corn portions containing various concentrations of natural aflatoxins and supplemented when appropriate with aflatoxin B1 were distributed to participating laboratories for testing. The assay is based on competition between an enzyme-conjugated aflatoxin B1 and (free) aflatoxins in the test sample for aflatoxin-specific antibodies coated onto interior surfaces of microtiter wells. After a wash step to remove all unbound aflatoxins, a substrate added to each well is catalyzed from a colorless to a blue solution by any bound enzyme-conjugated aflatoxin B1 present. The intensity of the color decreases as the amount of free aflatoxin B1 in the test portion increases. Final determination of aflatoxin concentrations can be made by either visual comparison with standard solutions or spectrophotometric comparisons (at 650 nm) to knowns. Overall correlation was good between ELISA and thin-layer chromatographic results for corn and roasted peanut products, with 93 and 98% correct responses for visual and instrumental determinations, respectively. For instrumental determinations of aflatoxin in corn and roasted peanuts in the less than or equal to 20 ng/g range, the relative standard deviations for repeatability (RSDr) were 14.9 and 41.4%, respectively, and the relative standard deviations for reproducibility (RSDR) were 45.7 and 43.5%, respectively. For instrumental determination of greater than 20 ng/g, the respective RSDr and RSDR values were 19.4 and 52.7% for corn and 23.3 and 23.3% for roasted peanuts.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

8.
A chemical cleanup procedure for low-level quantitative determination of aflatoxins in major economically important agricultural commodities using HPLC has been developed. Aflatoxins were extracted from a ground sample with MeOH/H2O (80:20, v/v), and after a cleanup step on a minicolumn packed with Florisil, aflatoxins were quantified by HPLC equipped with a C18 column, a photochemical reactor, and a fluorescence detector. Water/MeOH (63:37, v/v) served as the mobile phase. Recoveries of aflatoxins B1, B2, G1, and G2 from peanuts spiked at 5, 1.7, 5, and 1.7 ng/g were 89.5+/-2.2, 94.7+/-2.5, 90.4+/-1.0, and 98.2+/-1.1, respectively (mean+/-SD, %, n=3). Similar recoveries, precision, and accuracy were achieved for corn, brown and white rice, cottonseed, almonds, Brazil nuts, pistachios, walnuts, and hazelnuts. The quantitation limits for aflatoxins in peanuts were 50 pg/g for aflatoxin B1 and 17 pg/g for aflatoxin B2. The minimal cost of the minicolumn allows for substantial savings compared with available commercial aflatoxin cleanup devices.  相似文献   

9.
A method is described for simple and rapid determination of aflatoxins in corn, buckwheat, peanuts, and cheese. Aflatoxins were extracted with chloroform-water and were purified by a Florisil column chromatographic procedure. Column eluates were concentrated and spotted on a high performance thin layer chromatographic (HPTLC) plate, which was then developed in chloroform-acetone (9 + 1) and/or ether-methanol-water (94 + 4.5 + 1.5) or chloroform-isopropanol-acetone (85 + 5 + 10). Each aflatoxin was quantitated by densitometry. The minimum detectable aflatoxin concentrations (micrograms/kg) in various test materials were 0.2, B1; 0.1, B2; 0.2, G1; 0.1, G2; and 0.1, M1. Recoveries of the aflatoxins added to corn, peanut, and cheese samples at 10-30 micrograms/kg were greater than 69% (aflatoxin G2) and averaged 91%, B1; 89%, B2; 91%, G1; 78%, G2; and 92%, M1. The simple method described was compared with the AOAC CB method, AOAC BF method, and AOAC milk and cheese method. These methods were applied to corn, peanut, and cheese composites spiked with known amounts of aflatoxins, and to naturally contaminated buckwheat and cheese. Recoveries were much lower for the BF method compared with our simple method and the CB method.  相似文献   

10.
A direct competitive enzyme-linked immunosorbent assay (ELISA) screening method for aflatoxins at 20 ng/g was studied by 12 collaborators. Test samples of peanut butter were extracted by blending with methanol-water-hexane (55 + 45 + 100) and heating the test extracts on a steam bath; test samples of the other commodities were extracted by blending with methanol-water (80 + 20). All test extracts were filtered and the filtrates were diluted with buffer to a final methanol concentration of less than 30%. Each diluted filtrate was applied to a cup containing a filter with immobilized polyclonal antibodies specific to aflatoxins B1, B2, and G1. Aflatoxin B1-peroxidase conjugate was added, the cup was washed with water, and a mixture of hydrogen peroxide and tetramethylbenzidine was added. The test sample was judged to contain greater than or equal to 20 ng aflatoxins/g when, after exactly 1 min, no color was observed on the filter; when a blue or gray color developed, the test sample was judged to contain less than 20 ng aflatoxins/g. All collaborators correctly identified naturally contaminated corn and raw peanut positive test samples. No false positives were found for controls containing less than 2 ng aflatoxins/g. The correct responses for positive test samples spiked at levels of 10, 20, and greater than or equal to 30 ng aflatoxins/g (the ratio of B1:B2:G1 was 10:1:3) were 52, 86, and 96%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

11.
An AOAC/IUPAC (International Union of Pure and Applied Chemistry) collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column for the determination of aflatoxin. The test portion is extracted with methanol-water (7 + 3), filtered, diluted to less than 30% methanol with water, and applied to the affinity column. The column is washed with water and the concentrated aflatoxins are eluted with methanol. Total aflatoxins are determined by solution fluorometry with bromine (SFB), and individual toxins are determined by reverse-phase liquid chromatography with postcolumn derivatization with iodine (PCD). Corn naturally contaminated with aflatoxins, and peanuts, peanut butter, and corn containing added aflatoxins (B1:B2:G1:G2 = 7:1:3:1) were sent to 24 collaborators in the United States, France, Canada, and the Republic of South Africa. Twelve collaborators used the SFB method, 9 used the PCD method, and 3 used both SFB and PCD methods. Twenty collaborators completed the study (10 used the SFB method, 7 used the PCD method, and 3 used both SFB and PCD methods). Test portions were spiked at 10, 20, and 30 ng/g. For SFB analyses, recoveries of total aflatoxins were 123, 105, and 107%, respectively; the relative standard deviation for repeatability (RSDr) ranged from 11.75 to 16.57%, and the relative standard deviation for reproducibility (RSDR) ranged from 10.97 to 33.09%. For PCD analyses, recoveries were 81, 81, and 83%, respectively; the RSDr ranged from 5.20 to 17.22%, and the RSDR ranged from 4.68 to 50.77%. The RSDr for aflatoxins B1 and G1 for spiked test portions ranged from 5.45 to 23.55%, and the RSDR ranged from 4.21 to 57.28%.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
Thirteen laboratories in 7 different countries participated in a collaborative trial to evaluate the immunoaffinity column cleanup procedure with quantitation by fluorescence liquid chromatography (post-column derivatization) for the determination of aflatoxins in peanut butters. Participants were sent 10 randomly numbered samples of roasted peanut butter for analysis (5 pairs of undisclosed duplicates). Two of the pairs were "blank" peanut butters to which aflatoxin standards had been added; these "spiked" samples were used for recovery purposes. The other 3 pairs of samples were a nominal "blank" and 2 naturally contaminated peanut butters. A full statistical presentation of the results is given. Coefficients of variation (CVs) for the total aflatoxin determinations for mean levels of 4, 15, and 38 microns/kg were between 32 and 44% for the blank and 2 trial samples. Recovery levels for the 2 spiked samples were 51-67%, with aflatoxin B1 recovery of 60%. Relative standard deviations for method repeatability (RSDr) and reproductibility (RSDR) for the 3 trial samples were 15-26% and 33-45%, respectively.  相似文献   

13.
The amount of aflatoxin extracted from raw peanuts by using the water-slurry modification of AOAC Method II was determined for 49 different combinations of methanol concentrations and solvent/peanut ratio. Results indicate that the amount of aflatoxins B1 and B2 extracted from raw peanuts is a function of both methanol concentration and solvent/peanut ratio, and a cubic equation was developed, using regression techniques, to describe the combined effects. From the functional relationship, the predicted methanol concentration and solvent/peanut ratio that extracts the most aflatoxin B1 was computed to be 60.0% and 10.8 mL solvent/g peanuts, respectively. This combination extracted 12.1% more aflatoxin than did AOAC Method II.  相似文献   

14.
A simple, rapid, and solvent-efficient method for determining aflatoxins in corn and peanut butter is described. Aflatoxins B1, B2, G1, and G2 were extracted from 50 g sample with 200 mL methanol-water (85 + 15). A portion of the extract was diluted with 10% NaCl solution to a final concentration of 50% methanol, and then defatted with hexane. The aflatoxins were partitioned into chloroform. The chloroform solution was evaporated, and the residue was placed on a 0.5 g disposable silica gel column. The column was washed with 3 mL each of hexane, ethyl ether, and methylene chloride. Aflatoxins were eluted with 6 mL chloroform-acetone (9 + 1). The solvent was removed by evaporation on a steam bath, and the aflatoxins were determined using thin layer chromatography (TLC) with silica gel plates and a chloroform-acetone (9 + 1) developing solvent. Overall average recovery of aflatoxin B1 from corn was 82%, and the limit of determination was 2 ng/g. For mass spectrometric (MS) confirmation, aflatoxin B1 in the extract from 3 g sample (20 ng/g) was purified by TLC and applied by direct on-column injection at 40 degrees C into a 6 m fused silica capillary gas chromatographic column. The column was connected directly to the ion source. After injection, the temperature was rapidly raised to 250 degrees C, and the purified extract was analyzed by negative ion chemical ionization MS.  相似文献   

15.
A modification of the official method for ochratoxins and a screening method for zearalenone, aflatoxin, and ochratoxin is described and expanded to include citrinin and penicillic acid. The method uses 0.5N phosphoric acidchloroform (1+10) in the initial extraction; the extract is divided and eluted from 2 columns to provide a quantitative thin layer chromatographic (TLC) method for aflatoxin and ochratoxin in corn and dried beans. Aflatoxin and zearalenone are eluted from one column and ochratoxin, penicillic acid, and citrinin from the other. Ochratoxin A recoveries are low (50%) in peanuts. Zearalenone, penicillic acid, and citrinin were qualitatively recovered from corn and beans; zearalenone and penicillic acid were recovered from peanuts but citrinin was not. Several TLC solvents were used to separate interferences.  相似文献   

16.
A multimycotoxin thin layer chromatographic method is described for the analysis of corn. Aflatoxins are extracted from the samples with acetonitrile-water, and sodium bicarbonate is added to separate the acidic ochratoxin from zearalenone and aflatoxin B1. After chloroform extraction, 1N NaOH is added to separate zearalenone and aflatoxin B1. The separated mycotoxins are spotted on TLC plates, which are then examined under ultraviolet light. The following recoveries (%) were obtained for corn samples: aflatoxin B1 71, ochratoxin A 87, and zearalenone 85. The limits of detection for the respective mycotoxins were 2, 40, and 200 ppb.  相似文献   

17.
A high pressure liquid chromatographic method has been developed for determining aflatoxins B1, B2, G1, and G2 in peanut butter. The method is based on extraction with acidified aqueous methanol, partition of the aflatoxin into methylene chloride, and purification of the extract on a 2 g silica gel column. The extracted aflatoxins are resolved on a microparticulate (10 micrometer) porous silica gel column in ca 10 min with a water-washed chloroform-cyclohexane-acetonitrile solvent that contains 2% isopropanol. The fluorescence detection system determines aflatoxins B1, B2, G1, and G2 at low levels, i.e., 0.25 ppb B1, 0.5 ppb G1, and 0.2 ppb B2 and G2. Multiple assays of 5 samples of naturally contaminated peanut butters containing total aflatoxins (B1 + B2 + G1 + G2) at levels of 1, 2, 3, 9, and 17 ppb gave intralaboratory coefficients of variation of 7, 4, 4, 11, and 3%, respectively. Samples spiked at levels of 5, 9, and 17 ppb total aflatoxins showed recoveries of 79, 81, and 81%, respectively.  相似文献   

18.
A liquid chromatographic (LC) technique has been developed that uses the Mycosep multifunctional cleanup (MFC) column. MFC columns provide a rapid 1-step extract purification. They are designed to retain particular groups of compounds that may create interferences in analytical methods. At the same time, MFC columns allow compounds of interest to pass through. In the method presented, test samples are extracted in a blender with acetonitrile-water (9 + 1). A portion of the extract is forced through an MFC column designed especially for analysis of numerous mycotoxins. Analytical interferences are retained, while aflatoxins pass through the column. Aflatoxins B1 and G1 are converted to their hemiacetals by heating a mixture of purified extract and water-trifluoroacetic acid-acetic acid (7 + 2 + 1) at 65 degrees C for 8.5 min. An aliquot of this mixture is analyzed by isocratic LC with acetonitrile-water mobile phase and fluorescence detection. A detection limit of less than 0.5 ng/g for aflatoxin B1 was obtained. Average recoveries greater than 95% total aflatoxins (B1, B2, G1, and G2) and coefficients of variation of less than 3% were obtained. The method was successfully applied to the following commodities: corn, almonds, pista-chios, walnuts, peanuts, Brazil nuts, milo, rice, cottonseed, corn meal, corn gluten meal, fig paste, and mixed feeds.  相似文献   

19.
Roasting aflatoxin-contaminated corn will reduce toxin levels. A quantitative analysis for aflatoxin in roasted corn has been developed by modifying a cleanup technique for green coffee extracts approved as official first action by the AOAC. A chloroform extract is partially purified on a Florisil column, and thin layer chromatographic (TLC) plates are developed with methylene chloride-chloroform-isoamyl alcohol-formic acid (81+15+3+1). Recoveries average 101% and the sensitivity limit is 5 ppb aflatoxin B1. A 2-dimensional TLC procedure can also be used to separate the aflatoxins from background interferences.  相似文献   

20.
High pressure liquid chromatographic determination of aflatoxins in corn.   总被引：1，自引：0，他引：1  
A high pressure liquid chromatographic (HPLC) method is proposed for determining aflatoxins in corn. The sample is extracted with methanol-10% NaCl (4 + 1), pigments are precipitated with zinc acetate, and the extract is cleaned up on a small (2 g) silica gel column. Aflatoxins in the purified extract are resolved by normal phase HPLC on a microparticulate (10 micrometer) silica gel column with water-saturated chloroform-cyclohexane, acetonitrile solvent, and detected by fluorescence on a silica gel-packed flowcell. The method was compared with chloroform-water extraction of the official CB method on 15 samples of contaminated corn. In 5 of the 6 samples containing aflatoxins B1, B2, G1, and G2, methanol-10% NaCl extracted more aflatoxin than did cloroform-water, as measured both by HPLC and by thin layer chromatography. In samples containing only B1 and B2, the 2 extraction solvents were virtually equivalent. Agreement was good between HPLC and TLC for each extraction solvent. Average recovery of aflatoxins B1, B2, G1, and G2 added to yellow cornmeal at 3 levels was greater than 90%.  相似文献   

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