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1.
The Onley-Yip procedure for determining ethylenethiourea (ETU) in milk and crops was modified to reduce interferences by the ethylenebisdithiocarbamates (EBDCs). A 20 g crop-methanol extract is cleaned up by adsorbing the sample onto Gas-Chrom S. desorbing ETU, and eluting ETU from aluminum oxide with chloroform containing ethanol. ETU is converted to the S-butyl derivative for gas-liquid chromatography (GLC) and flame photometric detection (sulfur mode). For liquid chromatography (LC), ETU is cleaned up on another aluminum oxide column and injected directly. LC and GLC results are confirmed by thin layer chromatography. A cooking procedure based on conversion of EBDCs to ETU is included for surveying crops for possible EBDC content. Recoveries from 8 crops and milk fortified at 0.05 ppm ETU ranged from 73 to 100%.  相似文献   

2.
Milk is typically screened for beta-lactam antibiotics by nonspecific methods. Although these methods are rapid and sensitive, they are not quantitative and can yield false positive findings. A sensitive and specific method for the quantitation and mass spectral confirmation of five beta-lactam and two cephalosporin antibiotics commonly or potentially used in the dairy industry is described using high-performance liquid chromatography with tandem mass spectrometry. The antibiotics studied were ampicillin, amoxicillin, penicillin G, penicillin V, cloxacillin, cephapirin, and ceftiofur. The antibiotics were extracted from milk with acetonitrile, followed by reversed-phase column cleanup. The extract was analyzed by liquid chromatography coupled with a mass spectrometer, using a water/methanol gradient containing 1% acetic acid on a C-18 reversed-phase column. Determination was by positive ion electrospray ionization and ion trap tandem mass spectrometry. Quantitation was based on the most abundant product ions from fragmentation of the protonated ion for amoxicillin, cephapirin, ampicillin, and ceftiofur and on the fragmentation of the sodium adduct for penicillin G, penicillin V, and cloxacillin. The method was validated at the U.S. FDA tolerance or safe level and at 5 or 2.5 ng/mL for these compounds in bovine milk. Theoretical method detection limits in milk based on a 10:1 signal to noise ratio were 0.2 ng/mL (ampicillin), 0.4 ng/mL (ceftiofur), 0.8 ng/mL (cephapirin), 1 ng/mL (amoxicillin and penicillin G), and 2 ng/mL (cloxacillin and penicillin V) using a nominal sample size of 5 mL.  相似文献   

3.
Oxyfluorfen and oxyfluorfen amine were determined by liquid chromatography (LC) with ultraviolet (UV) and photoconductivity detection (PCD). A simple extraction procedure acceptably recovered both analytes from garbanzo beans over a wide range of fortifications (0.05 to 20 ppm) (83 +/- 4 for oxyfluorfen; 85 +/- 4 for oxyfluorfen amine). Percent recoveries decreased slightly as the fortification level decreased. Both analytes could be determined simultaneously at a concentration greater than 0.2 ppm in garbanzo beans. Detection limits were 3 ng for oxyfluorfen and 100 ng for oxyfluorfen amine using LC/UV, and 12 ng for both oxyfluorfen and oxyfluorfen amine with LC/PCD. Different knitted reaction coils and photoreactors were evaluated. Photoproduct yields and identification were determined by ion chromatography. The LC/PCD method measures oxyfluorfen and oxyfluorfen amine separately and has a shorter analysis time, while the standard method using gas chromatography measures total residues and is more sensitive.  相似文献   

4.
A simple and rapid method for determining 1-deoxynojirimycin (DNJ), a potent glucosidase inihibitor present in mulberry leaves (Morus alba and Morus bombysis), by high-performance liquid chromatography coupled to an evaporative light scattering detector (ELSD) has been developed. DNJ was separated from an extract of mulberry leaves on a TSKgel Amide-80 column, which is a representative column for hydrophilic interaction chromatography. During postcolumn detection, DNJ was detected by ELSD and concurrently identified by mass spectrometry. The detection limit was 100 ng. This method is sufficiently sensitive for determining DNJ in mulberry leaves and other related products.  相似文献   

5.
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   

6.
A solid-phase microextraction (SPME) method, coupled to liquid chromatography with diode array UV detection (LC-UV/DAD), for the simultaneous determination of cyclopiazonic acid, mycophenolic acid, tenuazonic acid, and ochratoxin A is described. Chromatographic separation was achieved on a propylamino-bonded silica gel stationary phase using acetonitrile/methanol/ammonium acetate buffer mixture (78:2:20, v/v/v) as mobile phase. SPME adsorption and desorption conditions were optimized using a silica fiber coated with a 60 microm thick polydimethylsiloxane/divinylbenzene film. Estimated limits of detection and limits of quantitation ranged from 3 to 12 ng/mL and from 7 to 29 ng/mL, respectively. The method has been applied to cornflake samples. Samples were subjected to a preliminary short sonication in MeOH/2% KHCO(3) (70:30, v/v); the mixture was evaporated to near dryness and reconstituted in 1.5 mL of 5 mM phosphate buffer (pH 3) for SPME followed by LC-UV/DAD. The overall procedure had recoveries (evaluated on samples spiked at 200 ng/g level) ranging from 74 +/- 4 to 103 +/- 9%. Samples naturally contaminated with cyclopiazonic and tenuazonic acids were found; estimated concentrations were 72 +/- 9 and 25 +/- 6 ng/g, respectively.  相似文献   

7.
A simple method for rapid determination of d- chiro-inositol (DCI) (a potent mediator of insulin metabolism) contained in tartary buckwheat ( Fagopyrum tataricum L. Gaench) was developed on the basis of high-performance liquid chromatography coupled to an evaporative light scattering detector (ELSD). DCI was separated from an extract of tartary buckwheat on an Alltech Prevail Carbohydrates ES 5 mum column. During postcolumn detection, DCI was detected by ELSD. The detection limit was 100 ng. This method was sensitive enough for determining DCI in tartary buckwheat and its related products.  相似文献   

8.
A reverse-phase liquid chromatographic (LC) method is described for simultaneously determining 5 coccidiostats--aklomide, dinsed, ethopabate, nitromide, and zoalene in chicken liver. The method entails blender extraction of 10 g liver with ethyl acetate, column chromatography through Sephadex LH-20 and neutral alumina, and LC analysis on a C18 column with UV detection at 260 nm. The drugs were eluted from Sephadex with methanol-benzene (10 + 90), from alumina with methanol-dichloromethane (10 + 90), and from C18 with acetonitrile-water (linear gradient: 25% acetonitrile for 10 min, increasing to 55% over 15 min; flow rate 1 mL/min). Liquid chromatography was completed in 40 min and calculations were based on peak height measurements. Average recoveries of the coccidiostats from fortified liver ranged from 72 to 97%, except for dinsed, which showed a relatively constant average recovery of 57%. The detection limit for the standards was 2.5 ng on column. Levels as low as 50 ng/g were detected in fortified liver samples.  相似文献   

9.
A liquid chromatographic (LC) method for determination of aflatoxicol in porcine liver was developed. Liver sample is homogenized with water, diluted with saturated Na2SO4 solution, and extracted with acetone. After filtration, less polar interferences are removed by partition with isooctane. Aflatoxicol in the aqueous fraction is partitioned into CHCl3. The extract is dried over anhydrous Na2SO4 and evaporated nearly to dryness at 35 degrees C under a gentle flow of dry filtered air or nitrogen. Residue is dissolved in CHCl3-hexane and applied to a hexane-activated silica cartridge. The cartridge is washed with hexane-CHCl3, then aflatoxicol is eluted with CHCl3-acetone. Purified extract is evaporated to dryness, dissolved in methanol, and analyzed by C18 reverse phase liquid chromatography using a water-CH3CN-acetic acid mobile phase and fluorescence detection. Recovery of aflatoxicol from spiked liver samples at levels ranging from 0.25 to 4.0 ng aflatoxicol/g wet tissue averaged 92% with a limit of detection of about 0.1 ng aflatoxicol/g liver.  相似文献   

10.
A high-performance liquid chromatography (HPLC) method with ultraviolet (UV) detection was developed for the detection of cefquinome (CEQ) residues in swine tissues. The limit of detection (LOD) of the method was 5 ng g(-1) for muscle and 10 ng g(-1) for fat, liver, and kidney. Mean recoveries of CEQ in all fortified samples at a concentration range of 20-500 ng g(-1) were 80.5-86.0% with coefficient of variation (CV) below 10.3%. Residue depletion study of CEQ in swine was conducted after five intramuscular injections at a dose of 2 mg kg(-1) of body weight with 24 h intervals. CEQ residue concentrations were detected in muscle, fat, liver, and kidney using the HPLC-UV method at 265 nm. The highest CEQ concentration was measured in kidney tissue during the study period, indicating that kidney was the target tissue for CEQ. CEQ concentrations in all examined tissues were below the accepted maximum residue limit (MRL) recommended by the Committee for Veterinary Medical Products of European Medical Evaluation Agency (EMEA) at 3 days post-treatment.  相似文献   

11.
A simple and rapid procedure for the separation and determination of inorganic, methyl, and ethyl mercury compounds was described using liquid chromatography (LC) followed by vapor generation inductively coupled plasma-mass spectrometry (VG-ICP-MS). Well resolved chromatograms were obtained within 5 min by reversed-phase liquid chromatography with a C8 column as the stationary phase and a pH 4.7 solution containing 0.5% v/v 2-mercaptoethanol and 5% v/v methanol as the mobile phase. The separated mercury compounds were converted to mercury vapors by an in situ nebulizer/vapor generation system for their introduction into ICP. The concentrations of NaBH4 and HNO3 required for vapor generation were also optimized. The method was applied for the speciation of mercury in reference materials NIST SRM 1568a Rice Flour and NIST SRM 1567a Wheat Flour and also rice flour and wheat flour samples purchased locally. The accuracy of the procedure was verified by analyzing the certified reference material NRCC DOLT-3 Dogfish Liver for methyl mercury. Precision between sample replicates was better than 13% for all the determinations. The detection limits of the mercury compounds studied were in the range 0.003-0.006 ng Hg mL(-1) in the injected solutions, which correspond to 0.02-0.06 ng g(-1) in original flour samples. A microwave-assisted extraction procedure was adopted for the extraction of mercury compounds from rice flour, wheat flour, and fish samples using a mobile phase solution.  相似文献   

12.
A procedure has been developed for the automated isolation of aflatoxin M1 from decreamed milk. The method uses on-line stopped flow dialysis and subsequent trace enrichment on a reverse-phase column. After a back-flush to the analytical liquid chromatography column, aflatoxin M1 is determined with fluorescence detection. Fully automated analysis is possible with reproducible dialysis recoveries above 50% (CV = 7.5%, n = 25 at the 50 ng/kg level) and determination levels of 20 ng/kg within 20 min.  相似文献   

13.
The analysis of nine macrolides is presented, including tulathromycin A (Draxxin), in beef, poultry, and pork muscle with a simple multiresidue extraction and analysis method using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The sample preparation method involves extraction with acetonitrile and defatting with hexane followed by dilution of the extracts for analysis. Separation of the nine macrolides was performed using an Atlantis dC 18, 3 mum, 3.9 mm x 20 mm minicolumn (guard column). Detection was carried out with two multiple reaction monitoring experiments per macrolide. The method detection limits (MDLs) were based on three times standard deviation of eight repeat spikes at 3.0 ng/g of a mix of the nine macrolides in the various tissues. The MDLs and retention times for the macrolides were as follows: lincomycin, 0.19 ng/g (t R = 5.00 min); tulathromycin, 0.46 ng/g (t R = 5.63 min); spiramycin, 0.21 ng/g (t R = 6.06 min); pirlimycin, 0.10 ng/g (t R = 6.04 min); clindamycin, 0.16 ng/g (t R = 6.20 min); tilmicosin, 0.29 ng/g (t R = 6.38 min); erythromycin, 0.19 ng/g (t R = 6.62 min); tylosin, 0.10 ng/g (t R = 6.72 min); and josamycin, 0.09 ng/g (t R = 6.98 min). Precision at 25 ng/g (n = 4) ranged from 2.3 to 9.4% for the compounds from beef muscle. Of interest is the detection of incurred residues of tulathromycin A in edible calf tissue at 0.10-7 mug/g, which is presented here for the first time.  相似文献   

14.
Quantification of the mycotoxin patulin by a stable isotope dilution assay.   总被引：1，自引：0，他引：1  
Two stable isotope dilution assays for the quantification of patulin [4-hydroxy-4H-furo[3,2-c]pyran-2(6H)-one] in foods were developed using (13)C-labeled patulin as the internal standard. One method was performed by means of LC/MS in negative electrospray ionization mode without derivatization; the other used HRGC/HRMS after trimethylsilylation of the patulin isotopomers. In comparison with previously reported methods based on high-performance liquid chromatography with UV detection, HRGC/HRMS of the derivatized samples showed better repeatability, higher recovery rates (96% at a spike level of 200 ng/L), and a 100 times lower detection limit (12 ng/L). In contrast, LC/MS showed a much lower performance as compared to HPLC/UV or HRGC/HRMS. Using HRGC/HRMS, the mycotoxin was quantified in many different fruit products and in molded wheat bread.  相似文献   

15.
A rapid method is described for the quantitative determination of patulin in apple juice. The mycotoxin is extracted from the sample with ethyl acetate and the extract is cleaned up by extraction with a sodium carbonate solution. Patulin is determined by reverse phase liquid chromatography using a muBondapak C18 column and a 254 nm ultraviolet detector. The lower detection limit in patulin standard solution is 0.32 ng and recovery is greater than 75%.  相似文献   

16.
Two liquid chromatographic methods that involve precolumn derivatization with o-phthaladehyde (OPA) and phenylisothiocyanate (PITC) with fluorescence and diode array UV detection for the determination of theanine have been developed. The chromatographic separations were achieved by reverse-phase high-performance liquid chromatography using octadecyl columns and gradient elution. The methods were applied to evaluate the theanine content of commercial tea leaves. The coefficient of variation of the peak area repeatability for within day (n = 8) and between day (n = 8 over 10 days) was lower than 3% for both of the methods. The estimated limit of detection (LOD) and limit of quantitation (LOQ) for the OPA method was 0.12 and 0.35 microg theanine, respectively. The PITC method was 500-fold more sensitive with LOD and LOQ values of 0.25 and 0.75 ng, respectively. The theanine content of the commercial tea samples varied from 2-5 mg/g leaf. The overall % recoveries for these methods ranged from 93-99.3. The sensitivity and simplicity of the method render them suitable for use in quality control laboratories.  相似文献   

17.
Bisphenol A (BPA) concentrations were determined in canned beverages, fruits, vegetables, and fat-containing foodstuffs bought in Austrian supermarkets. The analysis method consisted of sol-gel immunoaffinity chromatography followed by high-performance liquid chromatography with fluorescence detection. With one exception traces of BPA were detected in all samples. BPA recovery strongly depended on the food matrix, ranging from 27% in goulash to 103% in a lemon soft drink. The results obtained allow a more realistic picture of the BPA exposure caused by cans with an epoxy resin protective coating because--in contrast to several previous studies--only those fractions of the can contents that are actually consumed were analyzed. BPA concentrations ranging from 0.1 ng/mL (lemon soft drink) to 38 ng/g (ready-to eat soup from Thailand) were significantly lower than the European Union migration limit of 0.6 mg of BPA/kg of food.  相似文献   

18.
A sensitive and accurate detection method is of great importance in monitoring fusaproliferin levels in foods and animal feeds and evaluating its potential hazard to human and animal health. Several methods have been developed to detect fusaproliferin in cereals and cereal-related products, including thin-layer chromatography, high-performance liquid chromatography, enzyme-linked immunosorbent assay, liquid chromatography-mass spectrometry (MS), gas chromatography (GC), and GC-MS. However, these detection methods either suffer from low sensitivity, need expensive instruments, or are susceptible to interfering substances in the sample matrix. The GC-flame ionization detector method developed herein is sensitive, reliable, and easy to use for detecting fusaproliferin in corn and corn-based samples. Its detection limits were 0.04 ng for standard trimethylsilyl-fusaproliferin and about 5 ppb for fusaproliferin in corn samples. The limits of quantitation of this method were 0.15 ng fusaproliferin/injection and 20 ppb of fusaproliferin in corn samples. The recovery rates of fusaproliferin from corn samples spiked with 200, 1000, and 5000 ppb standard fusaproliferin were 109, 85.7, and 98.9% on average. The repeatability of the method was acceptable when evaluated by the Horwitz equation. Of the tested corn samples, three out of five sweet corn and the three yellow corn samples were found to have low levels of fusaproliferin (9.4-45.3 ppb). A moldy corn sample had a fusaproliferin content of 297 ppb.  相似文献   

19.
Sulfonamides are widely used as a feed additive in animal production in Japan. The present paper is a determination of 3 sulfonamides: sulfamethazine (SMZ), sulfamonomethoxine [SMX, 4-amino-N-(3-methoxypyrazinyl)-benzenesulfonamide], and sulfadimethoxine (SDX) in animal tissue and egg by liquid chromatography (LC). Tissues were extracted with acetonitrile and fat was removed by liquid/liquid partition. The sulfonamides were purified by an ODS cartridge column; then each compound was separated by an ODS LC column and detected at 268 nm. Quantification levels were 0.02 ppm for SMZ and SMX, and 0.04 ppm for SDX; detection limits were 0.01 ppm for SMZ and SMX, and 0.02 ppm for SDX. Calibration curves were linear between 2 and 40 ng for SMZ and SMX, and between 4 and 80 ng for SDX. Recoveries from muscle and egg samples spiked with 1-2 micrograms/10 g were 81-98%.  相似文献   

20.
A multimycotoxin method is presented to quantitate aflatoxins, ochratoxin A, zearalenone, secalonic acid D, and vomitoxin in grain dust. Dust spiked with these mycotoxins was extracted sequentially with methylene chloride followed by acetonitrile-water (86 + 14). Vomitoxin was recovered in the latter extract and all other mycotoxins were recovered in the methylene chloride. Aflatoxins and ochratoxin were quantitated by fluorescence measurement on silica thin layer chromatographic plates. The other mycotoxins were quantitated after cleanup by reverse phase liquid chromatography and ultraviolet detection. Recoveries from dust spiked in the parts per billion (ng/g) range were approximately 80% (SD = 15-29%) for all mycotoxins. Minimum detectable amounts ranged from less than 0.5 ng/g for aflatoxins to 20 ng/g for zearalenone.  相似文献   

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