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1.
A 2-step chromatographic separation, using both thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC), in conjunction with the high sensitivity of laser fluorometry permits extension of the detection limits of aflatoxin contamination in corn to 0.1 ppb (microgram/kg) with a 26% root mean square variation. Aflatoxin B1 is extracted from corn with water-methanol and cleaned up by TLC. The recovery of aflatoxin from the TLC plates was linear from 10 to 1000 pg. Aflatoxin B1 is converted to the more highly fluorescent B2A derivative by treatment with 1N HCl. Experiments with aflatoxin B1 standard establish a constant conversion to B2A over approximately 3 orders of magnitude in B1 concentration. An extract of the B2A aflatoxin derivative is injected onto a reverse phase HPLC column. A flowing droplet of eluant is irradiated by an amplitude-modulated 325 nm He-Cd ion laser beam, and fluorescence from the droplet is detected by a lock-in amplifier in phase with the laser modulation. Several chromatograms are presented that demonstrate the capability of this procedure for removing interfering components in the corn extract.  相似文献   

2.
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   

3.
Several methods have been developed to analyze peanuts for aflatoxin by using thin layer chromatography (TLC). These methods depend on solvent extraction of aflatoxin from a sample of the product. Unfortunately, solvent solutions used to extract aflatoxin from peanuts also extract measurable quantities of other compounds such as oils, fats, sugars, and protein. The volume of these extracted compounds causes error in measuring the proportion of the solvent solution analyzed for aflatoxin. Also, because the cleanup procedures for some methods are inadequate, the volume of some of these extracted compounds also causes error in measuring the proportion of the extracted aflatoxin placed on TLC plates. These 2 errors cause underestimation of aflatoxin concentrations by approximately 11, 14, and 5% for the CB method, the modified version of the BF method generally used for raw peanuts, and a water slurry method, respectively. The correction specified by the CB method for fats in the extraction solvent reduces the approximate error for the CB method from 11 to 1%.  相似文献   

4.
A method for the accurate one-dimensional thin layer chromatographic (TLC) determination of aflatoxins B1, B2, G1, and G2 in mixed feeds is presented. The aflatoxins are extracted from the sample with chloroform and purified by solvent partitioning. Each aflatoxin is separated from pulp interference by thin layer chromatography on aluminum-backed silica plates. The separated aflatoxins are detected by fluorescence densitometry. Average recoveries for samples spiked from 10 to 100 ppb B1 and G1 and from 3 to 30 ppb B2 and G2 are 82, 84, 95, and 94% for B1, B2, G1, and G2, respectively. The above recovery data, when analyzed for overall method repeatability, produced relative standard deviations of 6.8, 4.3, 6.9, and 7.6% for B1, B2, G1, and G2, respectively. Minimum detection level is less than 1 ppb for each aflatoxin. B1 is confirmed by trifluoroacetic acid derivative formation on a silica TLC plate.  相似文献   

5.
A simple and sensitive method is proposed for the determination of aflatoxin M1 in cheese. The ground cheese sample is extracted with acetone-water (3 + 1). Acetone is evaporated under vacuum, and the aqueous phase is passed through a C18 disposable cartridge. After the cartridge is washed with acetonitrile-water (1 + 9), the toxin is eluted with acetonitrile. The extract is then cleaned up on a silica cartridge. Final analysis is performed by 2-dimensional thin layer chromatography (TLC) combined with fluorodensitometry or by liquid chromatography on a reverse phase C18 column with fluorescence detection. Recovery is greater than 90%, and the coefficient of variation is 6% or less. The detection limit is in the range of 10 ng/kg. The identity of aflatoxin M1 is confirmed by formation of the M2a or acetyl-M1 derivative and rechromatography.  相似文献   

6.
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   

7.
A fast, efficient, and cost-effective method was developed for the analysis of aflatoxins in farm commodities with high-pigment content, such as chili powder, green bean, and black sesame. The proposed method involved matrix solid-phase dispersion (MSPD) and high-performance liquid chromatography (HPLC)-fluorescence detection (FLD) with postcolumn electrochemical derivatization in a Kobra cell. The MSPD procedure combined the extraction with neutral alumina and pigment cleanup with graphitic carbon black (GCB) in a single step. The recoveries of aflatoxins ranged from 88% to 95% with the relative standard deviations (RSD) less than 6% (n = 6). The limits of detection (LODs) were 0.25 ng/g aflatoxin B1, G1, and 0.10 ng/g aflatoxin B2, G2, respectively. The analytical results obtained by MSPD were compared to those of the immunoaffinity column (IAC) cleanup method. No significant differences were found between the two methods by t-test at the 95% confidence level.  相似文献   

8.
A systematic method is proposed for determination and confirmation of aflatoxin M1 in cheese by liquid chromatography (LC). A sample of cheese is extracted with chloroform, cleaned up on 2 silica gel columns followed by a Sep-Pak C18 cartridge, and chromatographed on a 5 microns octadecyl silica column with fluorometric detection. The sample extract or standard is treated with n-hexane-trifluoroacetic acid (TFA) (4 + 1) for 30 min at 40 degrees C. Analysis by LC with TFA-treatment of the extract provides quantitative data. Multiple assays of 5 samples of Gouda cheese spiked with aflatoxin M1 at levels of 0.5, 0.1, and 0.05 ng/g showed average recoveries of 93.2, 91.6, and 92.4%, with coefficients of variation of 2.63, 3.97, and 4.52%, respectively. Assay of 5 naturally contaminated cheeses resulted in 0.051-0.448 ng/g of aflatoxin M1. Limit of quantitation is about 0.01 ng/g. The identity of aflatoxin M1 is confirmed by treating aflatoxin M1 or the M2a derivative with TFA-methanol (or ethanol) (3 + 1). The TFA-methanol reaction products of M2a could be detected quantitatively.  相似文献   

9.
Comparative evaluation of commercially available aflatoxin test methods   总被引：1，自引：0，他引：1  
Five qualitative methods and 1 quantitative aflatoxin analytical method were compared with the Holaday-Velasco (HV) minicolumn and thin-layer chromatography (TLC) methods for corn in an evaluation involving 4 U.S. Department of Agriculture Federal Grain Inspection Service (USDA-FGIS) laboratories, 1 laboratory at the University of Georgia, and 1 laboratory at the University of Arizona. Samples analyzed included 1 set of artificially contaminated corn containing both aflatoxin B1 and B2 (ratio of B1:B2 of 92:8), 1 set of artificially contaminated corn containing only aflatoxin B1, and 1 set of naturally contaminated corn. Levels of total aflatoxin tested were 0, 10, 15, 20, 25, 30, and 40 ppb. Results of analysis of these samples with each method evaluated are reported. Chi-square analyses indicated that performance of the Afla-20-Cup, Aflatest, EZ-Screen, OXOID, and SAM-A methods was not statistically different from that of the HV minicolumn. Agri-Screen results were not statistically different from those obtained with TLC.  相似文献   

10.
An interlaboratory study of a negative ion chemical ionization mass spectrometric (MS) confirmation procedure for aflatoxin B1 was conducted in laboratories in the United States, England, and West Germany. Twelve partially purified, dry film extracts from naturally and artificially contaminated roasted peanuts, cottonseed, and ginger root containing varying quantities of aflatoxin B1 were distributed to the participating laboratories. The extracts required additional cleanup before MS analysis, using either an acidic alumina column and preparative thin layer chromatography (TLC) or a 2-dimensional TLC procedure. Recovery of purified aflatoxin B1 was influenced by the degree of recovery of sample from acid alumina and/or the TLC plate and incomplete elution of aflatoxin B1 from silica gel. Factors affecting MS confirmation included the purity and recovery of aflatoxin and MS instrument sensitivity. Aflatoxin B1 identity was confirmed in 19.5, 90.9, and 100% of samples containing less than 5, 5-10, and greater than 10 ng aflatoxin B1/g product, respectively, by solid probe introduction using full mass scans. The MS method has been adopted official first action.  相似文献   

11.
A method is described for determination of 4 macrolide antibiotics in livestock products. Erythromycin, tylosin, oleandomycin, and spiramycin were extracted from animal tissues, milk, and egg with acetonitrile at pH 8.5. Cleanup was done by adding sodium chloride and dichloromethane, evaporating the organic layer, and subsequent acid/base partitioning. After the antibiotics were separated by thin-layer chromatography (TLC), they were reacted with xanthydrol and could be detected as purple spots down to 0.02 mg/kg without interference by other commonly used therapeutic drugs (23 were tested). Anisaldehyde-sulfuric acid, cerium sulfate-molybdic acid, phosphomolybdic acid, and Dragendorff's reagent proved to be less sensitive as visualizing agents. For quantitation, TLC plates were scanned at 525 nm. Recoveries were between 71 and 96% for erythromycin and tylosin in liver, muscle, and egg at the 0.1-0.5 mg/kg level and 51% for erythromycin in milk at the 0.02 mg/kg level (coefficient of variation = 10-18%). Bioautography with Bacillus subtilis was used to confirm results, in addition to TLC analysis of derivatized antibiotics and liquid chromatography with electrochemical detection. Various derivatization procedures for erythromycin were investigated for improved ultra-violet or fluorescence detection in liquid chromatography.  相似文献   

12.
A study was conducted to determine the accuracy and precision of 3 AOAC methods, secs 26.026-26.031 (CB), secs 26.032-26.036 (BF), and secs 26.052-26.060 (cottonseed), and the Romer quantitative method for the thin-layer chromatographic (TLC) determination of aflatoxins B1, B2, G1, and G2 in raisins. The samples were spiked at a level of 10 micrograms total aflatoxins/kg. The TLC development systems were: ether-methanol-water (94 + 4.5 + 1.5) and chloroform-acetone (9 + 1). The interaction between the 4 methods and the 2 development systems was also studied. The average recoveries were 88, 80, 75, and 93% with coefficients of variation of 14.0, 10.4, 14.0, and 9.6% for aflatoxin B1 using the CB, BF, cottonseed, and Romer methods, respectively. Statistical analysis showed no difference in the results obtained using the 2 TLC development systems.  相似文献   

13.
A method was developed for the determination of aflatoxin B1 in commercially prepared feeds. The method incorporates methylene chloride and citric acid solution extraction, cleanup on a small silica gel column, and thin layer chromatography for quantitation. Commercial turkey starter, catfish chow, medicated pig starter, broiler finisher, rabbit chow, horse feed, rat chow, and dog chow were investigated. The feeds were spiked with naturally contaminated corn at 4 different levels of aflatoxin B1 (16-130 microgram/kg). Three assays were run on each of the 32 combinations of feed and levels of aflatoxin. Mean recoveries were 85.9-92.8% at levels of 16.5, 32.9, 65.8, and 131.6 micrograms/kg. The relative standard deviation per assay was 18.6%. This method is more rapid and less involved than most previously published methods for mixed feeds.  相似文献   

14.
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   

15.
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.  相似文献   

16.
A joint project was undertaken by the Food Safety and Inspection Service (FSIS) and the Agriculture Research Service branches of the U.S. Department of Agriculture to determine the presence of aflatoxins in the U.S. meat supply during a drought year. In 1988, high incidences of aflatoxins occurred in corn grown in regions of the Midwest, Southeast, and South. Six states were identified as having serious aflatoxin contamination in their corn crop: Virginia, North and South Carolina, Texas, Iowa, and Illinois. Swine liver and pillars of diaphragm (muscle) tissues were sampled by federal FSIS Inspectors in plants located in these states. A worstcase sampling plan was conducted. Samples were taken in January 1989 from hogs fed corn soon after harvest and in April 1989 from hogs fed corn originally stored and then fed in the spring. A modification of the official AOAC method for the thin-layer chromatography (TLC) determination of aflatoxins in animal tissue was used to permit quantitation by LC with fluorescence detection. The official AOAC TLC confirmation of identity method was used to confirm all positive samples with B1 concentrations greater than 0.04 ppb and M1 concentrations greater than 0.1 ppb. Sixty samples in the January group and 100 samples in the April group were assayed. Concentrations of aflatoxins B1 and M1 in the first group of pig livers ranged from 0.04 to 0.06 ppb. The identity of aflatoxin B1 was confirmed in all positive samples. Aflatoxin M1 could not be confirmed in any of the positive liver samples because the method was insufficiently sensitive for this aflatoxin.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
The minicolumn screening method for aflatoxins was collaboratively tested on naturally contaminated almonds. The nuts were extracted, and the extract was cleaned up and applied to a Velasco-type minicolumn. This permits the detection of total aflatoxins (B1, B2, G1, G2) as a fluorescent band on the Florisil layer of the column. The results of 20 collaborators are presented. Samples containing 0, 2, 5, 10, and 25 ng aflatoxin/g were analyzed. Ninety-six per cent of the samples containing 5--25 ng total aflatoxins/g and 83% of the negative samples were correctly identified. The method has been adopted as official first action for detection of total aflatoxin levels of greater than or equal to 5 ng/g.  相似文献   

18.
Liquid chromatographic determination of aflatoxin M1 in milk   总被引：1，自引：0，他引：1  
The official AOAC method for aflatoxin M1 in milk was modified by replacing cellulose column chromatography with cartridge chromatographic cleanup and replacing thin layer chromatographic (TLC) determination with liquid chromatographic (LC) quantitation to yield a new method for bovine and porcine milk. An acetone extract of milk is treated with lead acetate and defatted with hexane, and M1 is partitioned into chloroform as in the AOAC method. Chloroform is removed by evaporation under a stream of nitrogen at 50 degrees C. The residue is dissolved in chloroform, the vessel is rinsed with hexane, and the 2 solutions are applied in sequence to a hexane-activated silica Sep-Pak cartridge. Less polar impurities are removed with hexane-ethyl ether, and M1 is eluted with chloroform-methanol, and determined by C18 reverse phase LC using fluorescence detection. Recoveries of M1 added to bovine milk at 0.25, 0.50, and 1.0 ng/mL were 90.8, 93.4, and 94.1%, respectively. The limit of detection was less than 0.1 ng M1/mL for both bovine and porcine milk.  相似文献   

19.
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   

20.
A method is presented for the detection of polysorbates (PSs) in 8 kinds of processed foods by colorimetric and thin-layer chromatographic (TLC) techniques. The PSs are extracted from processed foods with a mixture of methylene chloride and ethanol by using an Extrelut column. The extract is further purified by using a silica gel column. The PS extract is complexed with cobalt-thiocyanate (Cothiocyanate) reagent and is determined spectrophotometrically at 620 nm. The recoveries and coefficients of variation for 8 kinds of processed foods fortified with 0.1% PS 80 were 67.9-94.6% and 4.0-11.3%, respectively. The detection limit of TLC corresponded to 50 mg PS 80/kg. PS identity was confirmed by infrared spectrophotometry of PS extract, and gas chromatography of fatty acids and thin layer chromatography of POE-sorbitan residues after saponification.  相似文献   

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