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1.
A manual vacuum manifold and an automated solid phase extraction (ASPEC) system were applied for purification of ochratoxin A and zearalenone in wheat, rye, barley, and oat samples with immunoaffinity columns followed by separation with a high-performance liquid chromatograph and fluorescence detection. The immunoaffinity columns for manual sample purification were purchased from a different manufacturer than were those for the automated system. The limit of detection (LOD) for the method for ochratoxin A with a vacuum manifold and ASPEC was 0.1 microg/kg. For the method for zearalenone, the LODs were 1.5 microg/kg with a vacuum manifold and 3 microg/kg with ASPEC. For the methods for ochratoxin A at spiking levels of 0.6 and 2.5 microg/kg, mean recoveries for different cereals varied from 68 to 106%. For the methods for zearalenone, mean recoveries varied from 78 to 117% at spiking levels of 9 and 25 microg/kg. The relative standard deviations of repeatability with various cereals employing both methods were 2-15 and 2-19% for ochratoxin A and zearalenone, respectively.  相似文献   

2.
The potential for the Fusarium mycotoxins 4-deoxynivalenol (DON) and zearalenone (ZON) to enter the human food chain through contaminated eggs was assessed using a controlled feed study. Four groups of laying hens (eight in each group) were fed a diet that included differing amounts of naturally contaminated wheat containing DON ( approximately 20 mg kg(-1)) and ZON (0.5 mg kg(-1)). Eggs were collected and pooled from each group on a daily basis. Pooled samples were analyzed by liquid chromatography with mass spectrometry detection (LC-MS/MS). The method allowed DON, other type B trichothecenes, ZON, and its metabolites to be determined in a single multi-residue analysis. The selectivity of the MS/MS procedure allowed cleanup to be minimized (for DON, cleanup by immunoaffinity column was used) or eliminated (for ZON). The limits of detection of 0.01 microg kg(-1) for DON and 0.1 microg kg(-1) for ZON in eggs were lower than previously published methods. None of the samples analyzed had detectable levels of ZON or its metabolites. Although maximum levels of DON contamination (10 mg kg(-1) feed) were relatively high, no adverse effects were observed on egg production. On the basis of the determined DON levels in the hen's diet and the determined levels of DON in the corresponding eggs, transmission rates of 15 000:1, 18 000:1, and 29 000:1 for treatment levels 5, 7.5, and 10 mg DON kg(-1) feed, respectively, were found. These results show that, although eggs could be a human exposure route for DON, the levels are insignificant compared to the other sources, although the presence of metabolites of DON was not studied.  相似文献   

3.
Resistance to mycotoxin contamination was compared in field samples harvested from 45 commercial corn (maize) hybrids and 5 single-cross aflatoxin-resistant germplasm lines in years with high and moderate heat stress. In high heat stress, mycotoxin levels were (4.34 +/- 0.32) x 10(3) microg/kg [(0.95-10.5 x 10(3) microg/kg] aflatoxins and 11.2 +/- 1.2 mg/kg (0-35 mg/kg) fumonisins in commercial hybrids and 370 +/- 88 microg/kg (140-609 microg/kg) aflatoxins and 4.0 +/- 1.3 mg/kg (1.7-7.8 mg/kg) fumonisins in aflatoxin-resistant germplasm lines. Deoxynivalenol was detected (one-fourth of the samples, 0-1.5 mg/kg), but not zearalenone. In moderate heat stress, mycotoxin levels were 6.2 +/- 1.6 microg/kg (0-30.4 microg/kg) aflatoxins and 2.5 +/- 0.2 mg/kg (0.5-4.8 mg/kg) fumonisins in commercial hybrids and 1.6 +/- 0.7 microg/kg (0-7 microg/kg) aflatoxins and 1.2 +/- 0.2 mg/kg (0.5-3.0 mg/kg) fumonisins in aflatoxin-resistant germplasm lines. The results are consistent with heat stress playing an important role in the susceptibility of corn to both aflatoxin and fumonisin contamination, with significant reductions of both aflatoxins and fumonisins in aflatoxin-resistant germplasm lines.  相似文献   

4.
Corn samples spiked at levels of 100, 300, 1000, and 2000 mug zearalenone/kg were sent to 22 collaborators for analysis by the Eppley method. All samples were yellow corn except one white corn sample spiked at 2000 mug/kg. Results from 16 collaborators were statistically analyzed. Only 4 of 16 collaborators detected zearalenone in the sample containing 100 mu/kg, but 11 detected the toxin in the sample containing 300 mug/kg. Average recoveries from all samples were 129% at 300 mug/kg, 101% at 1000 mug/kg, and 88% at 2000 mug/kg. The between-laboratory coefficients of variation were 53.0% at 300 mug/kg, 38.2% at 1000 mug/kg, and 27.0% at 2000 mug/kg. Five naturally contaminated corn samples, one in triplicate, were also provided. The mean level of zearalenone in the naturally contaminated samples ranged from 431 to 7622 mug/kg. The mean coefficient of variation for all samples was 40.5%. Two collaborators measured quantities of zearalenone on thin layer chromatographic plates densitometrically. Their results were not included in the statistical analysis, but the results indicated that densitometric measurement, given proper dilutions of solutions, could be used. The method has been adopted as official first action.  相似文献   

5.
A group of five heifers were fed for 84 days with 2 kg of zearalenone-contaminated oats (1370 microg/kg) resulting in an average daily intake of 2740 microg of zearalenone per animal. In a parallel experiment five heifers were implanted with two 25 mg zeranol pellets, one at the beginning of the study and one after 42 days, and fed with 2 kg of "blank" control oats (79 microg/kg, daily intake = 158 microg). A third group of five animals were also fed with 2 kg of "blank" oats and served as control. Urine samples of all animals were collected every 5-6 days during the whole period of the study. Animals of all three groups were killed 84 days after the beginning of the feeding study. Tissue samples (back, femoral region, liver, and residues of implanted pellets) were taken during post-mortem investigations. The content of zearalenone and zeranol and their metabolites in urine and tissue samples was established by an analytical method combining solid-phase extraction and high-performance liquid chromatography-tandem mass spectrometry. Urinary excretion rates of zeralenone and zeranol were calculated from these results.  相似文献   

6.
A quantitative and confirmatory method for the analysis of trinexapac (free acid metabolite of trinexapac-ethyl) in wheat is described. Residues were extracted from wheat with acetonitrile in aqueous phosphate buffer (pH 7) overnight. The extract was directly injected into the HPLC system. Chromatographic separation was achieved on an octadecylsilica column, and detection was performed by negative ion electrospray ionization tandem mass spectrometry. The precursor ion of trinexapac [M - H](-) at m/z 223 was subjected to collisional fragmentation with argon to yield two intense diagnostic product ions at m/z 135 and 179, respectively. Accuracy and specificity for routine analysis of trinexapac were demonstrated. The validated concentration range was 10-200 microg/kg based on a 0.10 g/mL wheat sample extract. Recoveries were within the range of 71-94%, with associated relative standard deviations better than 10%. The limit of detection for trinexapac in wheat was estimated at 5 microg/kg. The method has been applied to a survey of 100 samples of wheat. In 46% of the samples analyzed, a quantifiable amount of trinexapac was detected, ranging from 10 to 110 microg/kg. It has been demonstrated that analyses of trinexapac accurately reflect the total amount of residues of the plant growth regulator, trinexapac-ethyl, in the wheat samples following field application. No residues of the parent compound, trinexapac-ethyl, in wheat were detected.  相似文献   

7.
To investigate possible co-occurrences of type B trichothecenes and zearalenone within a Fusarium culmorum-infected wheat harvest lot, kernels were fractionated into six groups by visual criteria. The Fusarium-damaged kernels were subdivided into white, shrunken, and red kernel groups, and the remaining kernels were sorted into healthy, black spotted, and nonspecific groups. The distribution patterns of nivalenol, deoxynivalenol, zearalenone, and ergosterol were determined for possible correlations. Significant correlations between the distribution patterns were found for the mycotoxins and ergosterol for the grouped kernels (r = 0.997-0.999, p < 0.0001). Additionally, remarkably outstanding levels of nivalenol (24-fold more than the mean at 1.16 mg/kg), deoxynivalenol (27-fold more than the mean at 0.16 mg/kg), zearalenone (25-fold more than the mean at 77 microg/kg), and ergosterol (17-fold more than the mean at 13.4 mg/kg) were found in the red kernel group. Further, detailed mycotoxin and ergosterol analyses were carried out on various segments (kernel surface, conidia, bran, and flour) of the red kernels. However, the mycotoxin and ergosterol distribution profiles revealed nonsignificant correlations for these kernel segments, with the exception of deoxynivalenol and nivalenol, which were moderately correlated (r = 0.948, p = 0.035).  相似文献   

8.
In this work, the occurrence of ochratoxin A (OTA) in 170 samples of cocoa products of different geographical origins was studied. An immunoaffinity column with HPLC separation was developed to quantify low levels of OTA in cocoa bean, cocoa cake, cocoa mass, cocoa nib, cocoa powder, cocoa shell, cocoa butter, chocolate, and chocolate cream with >80% recoveries. The method was validated by performing replicate analyses of uncontaminated cocoa material spiked at three different levels of OTA (1, 2, and 5 microg/kg). The data obtained were related on the acceptable safe daily exposure for OTA. The highest levels of OTA were detected in roasted cocoa shell and cocoa cake (0.1-23.1 microg/kg) and only at minor levels in the other cocoa products. Twenty-six cocoa and chocolate samples were free from detectable OTA (<0.10 microg/kg). In roasted cocoa powder 38.7% of the samples analyzed contained OTA at levels ranging from 0.1 to 2 microg/kg, and 54.8% was contaminated at >2 microg/kg (and 12 samples at >3 microg/kg). Ochratoxin A was detected in cocoa bean at levels from 0.1 to 3.5 microg/kg, the mean concentration being 0.45 microg/kg; only one sample exceeded 2 microg/kg (4.7%). In contrast, 51.2% of cocoa cake samples contained OTA at levels > or =2 microg/kg, among which 16 exceeded 5 microg/kg (range of 5-9 microg/kg). These results indicate that roasted cocoa powder is not a major source of OTA in the diet.  相似文献   

9.
Two methods for the determination of dichlorvos in durum wheat by electrochemical assay and gas chromatography, respectively, have been developed. Dichlorvos, an organophosphorus anticholinesterase pesticide, was extracted from wheat with hexane, and the filtered extract was directly analyzed by gas chromatography with nitrogen-phosphorus flame detection (NPD). Recoveries of dichlorvos from milled wheat spiked at 0.25-1.5 microg/g ranged from 96.5 to 100.9%, and the limit of detection was 0.02 microg/g. The electrochemical assay was based on the detection of choline, the acetylcholinesterase product, via a choline oxidase biosensor. An aliquot of the filtered hexane extract was partitioned with phosphate buffer solution, and the organic layer was evaporated prior to electrochemical analysis. A limit of detection of 0.05 microg/g of dichlorvos was obtained with mean recoveries of 97-103% at spiking levels of 0.25-1.5 microg/g. A good correlation (r = 0.9919) was found between the results obtained with the electrochemical and those obtained with the gas chromatographic methods. The electrochemical method was peer-validated in two laboratories that analyzed 10 blind samples (5 duplicates), including a blank and 4 spiked samples with dichlorvos at levels of 0.25, 0.60, 1.00, and 1.50 microg/g. Within-laboratory repeatability (RSDr) and between-laboratory reproducibility (RSDR) ranged from 5.5 to 7.8% and from 9.9 to 17.6%, respectively.  相似文献   

10.
Deoxynivalenol and zearalenone are among the most prevalent toxins produced by Fusarium spp. They have been investigated in food and feed products for decades but rarely in the environment. We therefore established solid-phase extraction and liquid chromatography-mass spectrometry (LC-MS) methods to quantify these mycotoxins at trace concentrations in aqueous natural samples. In a model emission study, we inoculated a winter wheat field with Fusarium graminearum and subsequently monitored deoxynivalenol and zearalenone in its drainage water. Before during and after harvest in June and July 2007, these toxins were emitted in concentrations from 23 ng/L to 4.9 microg/L for deoxynivalenol and from not detected to 35 ng/L for zearalenone. Simultaneously, in July and August 2007, deoxynivalenol was also detected in a number of Swiss rivers in concentrations up to 22 ng/L and zearalenone was present in several river samples below the method quantification limit. Other mycotoxins might be emitted from Fusarium-infected fields as well, because some of them are produced in similar amounts as deoxynivalenol and zearalenone and exhibit similar or even higher water solubility than deoxynivalenol. The ecotoxicological consequences of the presence of mycotoxins in surface waters remain to be elucidated.  相似文献   

11.
Polyclonal antibodies were produced for Ochratoxin A (OA) by injecting OA-bovine serum albumin (BSA) conjugate subcutaneously at multiple sites into a New Zealand White inbred rabbit. Antiserum could be used at a dilution exceeding 1:100 000 in an indirect competitive enzyme-linked immunosorbent assay (ELISA), and detected OA concentrations up to 0.1 ng/mL. The 50% inhibition binding (I(50)) of OA was 5 ng/mL. Antibodies did not react with ochratoxin B, coumarin, 4-hydroxycoumarin, L-phenylalanine, and aflatoxin B1. OA contamination in chilies (Capsicum annum L.) collected from commercial markets and cold storage units was determined. The mean recoveries from OA-free chilies spiked with 1 to100 microg of OA per kg of chili sample were 90-110% with a standard deviation of <10%. Of 100 chili samples tested, 26 were found to contain over 10 microg/kg of OA. In 12 samples the OA concentration varied from 10 to 30 microg/kg, in 10 samples from 30 to 50 microg/kg, in 3 samples from 50 to100 microg/kg, and in one sample it was 120 microg/kg. This is the first record in India of OA in chilies, a major component of cooked foods in this country, and it is noteworthy that OA contamination exceeded the permissible limit for human consumption of less than 20 microg/kg in over 26% of the market samples tested.  相似文献   

12.
Conjugated mycotoxins, in which the toxin is usually bound to a more polar substance like glucose, are referred to as masked mycotoxins, as these substances escape routine detection methods but can release their toxic precursors after hydrolysis. This is the first report on the natural occurrence of a glucoside of deoxynivalenol (DON) in Fusarium-infected wheat and maize. To obtain appropriate standards, we chemically synthesized deoxynivalenol-3-beta-D-glucopyranoside (DON-3-glucoside) and deoxynivalenol-15-beta-D-glucopyranoside (DON-15-glucoside). The synthesis products were characterized by liquid chromatography-tandem mass spectrometry. The DON-glucosides showed different collision-induced dissociation (CID) fragmentation behaviors and could therefore be distinguished. Wheat plants were either treated with DON (n = 52) or with Fusarium spp. (n = 4) at anthesis, and after harvest, wheat ears were analyzed for DON and DON-glucosides. All 56 treated wheat samples contained DON and a DON-glucoside with the same retention time, molecular mass, and CID fragmentation behavior as the synthetic DON-3-glucoside. Moreover, the DON-glucoside was also found in two out of three analyzed naturally DON-contaminated maize and in five out of five naturally contaminated wheat samples, in a range from 4 to 12% of the DON concentration. To further confirm the identity of the DON-glucoside, the compound was isolated from wheat extracts and characterized as DON-3-glucoside with NMR. The results of this study indicate the importance to consider both DON and DON-3-glucoside with regard to food and feed safety.  相似文献   

13.
In this study an LC-MS/MS multitoxin method covering a total of 247 fungal and bacterial metabolites was applied to the analysis of different foods and feedstuffs from Burkina Faso and Mozambique. Overall, 63 metabolites were determined in 122 samples of mainly maize and groundnuts and a few samples of sorghum, millet, rice, wheat, soy, dried fruits, other processed foods and animal feeds. Aflatoxin B(1) was observed more frequently in maize (Burkina Faso, 50% incidence, median = 23.6 μg/kg; Mozambique, 46% incidence, median = 69.9 μg/kg) than in groundnuts (Burkina Faso, 22% incidence, median = 10.5 μg/kg; Mozambique, 14% incidence, median = 3.4 μg/kg). Fumonisin B(1) concentrations in maize were higher in Mozambique (92% incidence, median = 869 μg/kg) than in Burkina Faso (81% incidence, median = 269 μg/kg). In addition, ochratoxin A, zearalenone, deoxynivalenol, nivalenol, and other less reported mycotoxins such as citrinin, alternariol, cyclopiazonic acid, sterigmatocystin, moniliformin, beauvericin, and enniatins were detected. Up to 28 toxic fungal metabolites were quantitated in a single sample, emphasizing the great variety of mycotoxin coexposure. Most mycotoxins have not been reported before in either country.  相似文献   

14.
When wheat was grown under conditions of severe sulfate depletion, dramatic increases in the concentration of free asparagine were found in the grain of up to 30 times as compared to samples receiving the normal levels of sulfate fertilizer. The effect was observed both in plants grown in pots, where the levels of nutrients were carefully controlled, and in plants grown in field trials on soil with poor levels of natural nutrients where sulfate fertilizer was applied at levels from 0 to 40 kg sulfur/Ha. Many of the other free amino acids were present at higher levels in the sulfate-deprived wheat, but the levels of free glutamine showed increases similar to those observed for asparagine. In baked cereal products, asparagine is the precursor of the suspect carcinogen acrylamide, and when flours from the sulfate-deprived wheat were heated at 160 degrees C for 20 min, levels of acrylamide between 2600 and 5200 microg/kg were found as compared to 600-900 microg/kg in wheat grown with normal levels of sulfate fertilization.  相似文献   

15.
A multicolumn solid-phase extraction cleanup for the determination of organophosphorus (OP) and organochlorine (OC) pesticides plus PCB congeners in virgin olive oil is presented. The method involves dissolution of the olive oil in hexane, followed by a cleanup system using a diatomaceous earth column (Extrelut-QE) with reversed (C(18)) and normal (alumina) phase SPE columns. Determination of OPs was by GC-NPD, while the OCs and PCBs were analyzed using GC-ECD. Recovery assays for OPs varied from 81.7% to 105.3%, for OCs ranged between 74.3% and 99.4%, while for PCBs were from 60.1% to 119.2%. Quantitation limits ranged from 10 to 25 microg/kg olive oil for OPs, and from 1 to 6 microg/kg olive oil for OCs and PCBs. In the case of positive samples, the confirmation of pesticide identity was performed by ion-trap GC-MS/MS. The applicability of the method was assayed with 19 virgin olive oil samples collected from different olive mills of Aragón (Spain). Only one OP pesticide (acephate) was detected in one sample at a concentration of 10 microg/kg. Organochlorine pesticides were found in 5-47% of samples at very low levels ranging from 1.5 to 5.2 microg/kg. PCBs were found in 20-90% of samples, showing concentrations between 2.3 and 17.3 microg/kg.  相似文献   

16.
Aflatoxins are a group of very carcinogenic mycotoxins that can be found on a wide range of food commodities including nuts, cereals, and spices. In this study, the first LC-MS/MS stable isotope dilution assay (SIDA) for the determination of aflatoxins in foods was developed. The development of this method was enabled by easily accessible isotope-labeled (deuterated) aflatoxins B2 and G2, which were synthesized by catalytic deuteration of aflatoxin B1 and G1, purified, and well-characterized by NMR and MS. All four aflatoxins of interest (B1, B2, G1, and G2) were quantified in food samples by using these two labeled internal standards. The response factors (RF) of the linear calibrations were revealed to be matrix independent for labeled aflatoxin B2/aflatoxin B2 and labeled aflatoxin G2/aflatoxin G2. For labeled aflatoxin B 2/aflatoxin B 1 and labeled aflatoxin B2/aflatoxin G1 matrix-matched calibration was performed for the model matrices almonds and wheat flour, showing significant differences of the RFs. Limits of detection (LOD) were determined by applying a statistical approach in the presence of the two model matrices, yielding 0.31 microg/kg (aflatoxin B1), 0.09 microg/kg (aflatoxin B2), 0.38 microg/kg (aflatoxin G1), and 0.32 microg/kg (aflatoxin G2) for almonds (similar LODs were obtained for wheat flour). Recovery rates were between 90 and 105% for all analytes. Coefficients of variation (CV) of 12% (aflatoxin B1), 3.6% (aflatoxin B2), 14% (aflatoxin G1), and 4.8% (aflatoxin G2) were obtained from interassay studies. For further validation, a NIST standard reference food sample was analyzed for aflatoxins B1 and B2. The method was successfully applied to determine trace levels of aflatoxins in diverse food matrices such as peanuts, nuts, grains, and spices. Aflatoxin contents in these samples ranged from about 0.5 to 6 microg/kg.  相似文献   

17.
The liquid chromatographic (LC) method described, suitable for use with both blood plasma and urine, is applicable for determination of zearalenone and alpha-zearalenol at levels as low as 0.5 ng/mL plasma and 5 ng/mL urine. The sample is incubated overnight with beta-glucuronidase to analyze for both conjugated and unconjugated forms of zearalenone. The next day, the sample is acidified with H3PO4, extracted with chloroform, and evaporated to dryness. The residue is dissolved in toluene and loaded onto a silica gel cartridge which is washed with toluene and eluted with toluene-acetone (88 + 12). The eluate is evaporated, and the residue is dissolved in chloroform, extracted with 0.18M NaOH, neutralized with H3PO4, and re-extracted with chloroform. The chloroform extract is evaporated, dissolved in mobile phase for LC, and injected onto a normal phase column under the following chromatographic conditions: mobile phase of water-saturated dichloromethane containing 2% 1-propanol, and fluorescence detector, excitation wave-length 236 nm, and 418 nm cut-off emission filter. Recoveries of zearalenone and its metabolites from blood plasma and urine are 80-89% in the range 2.0-10 ng standard/mL plasma, and 81-90% in the range 10-30 ng standard/mL urine. This method was used to analyze blood and urine samples from a pig fed zearalenone-contaminated feed (5 mg/kg), corresponding to 80 micrograms/kg body weight. Zearalenone was rapidly metabolized to alpha-zearalenol, which appeared in the blood only 30 min after feeding. Almost all zearalenone and alpha-zearalenol was found conjugated with glucuronic acid in both blood plasma and urine.  相似文献   

18.
Because of its pronounced estrogenicity, zearalenone may be of concern not only in the aqueous but also in the terrestrial environment. Therefore, we developed several analytical methods to quantify zearalenone in different solid matrices of agroenvironmental relevance (i.e., plant organs, soil, manure, and sewage sludge). The use of D(6)-zearalenone as the internal standard (IS) was essential to render the analytical method largely matrix-independent because it compensated for target analyte losses during extract treatment and ion suppression during ionization. Soil and sewage sludge samples were extracted with Soxhlet, whereas plant material and manure samples were extracted by liquid solvent extraction at room temperature. Absolute recoveries for zearalenone were 70-104% for plant materials, 105% for soil, 76% for manure, and 30% for sewage sludge. Relative recoveries ranged from 86 to 113% for all matrices, indicating that the IS was capable to largely compensate for losses during analysis. Ion suppression, between 8 and 74%, was in all cases compensated by the IS but influenced the method quantification levels. These were 3.2-26.2 ng/g(dryweightdw) for plant materials, 0.7 ng/g(dw) for soil, 12.3 ng/g(dw) for manure, and 6.8 ng/g(dw) for sewage sludge. Plant material concentrations varied from 86 ng/g(dw) to more than 16.7 microg/g(dw), depending on the organ and crop. Soil concentrations were between not detectable and 7.5 ng/g(dw), depending on the sampling depth. Zearalenone could be quantified in all manure samples in concentrations between 8 and 333 ng/g(dw). Except for two of the 85 investigated sewage sludge samples, zearalenone concentrations were below quantification limit.  相似文献   

19.
Wheat samples (102 lots) were collected from Virginia, North Carolina, southeastern Missouri, southern Illinois, and Kentucky. Soybean samples (180 lots) were collected from Virginia, Illinois, Iowa, Minnesota, Nebraska, Alabama, Arkansas, and Texas. Samples of both commodities were analyzed for zearalenone, aflatoxin, and ochratoxin by the Eppley method. None of the 3 mycotoxins was detected in soybeans. Aflatoxins and ochratoxin A were not detected in wheat, but zearalenone was detected in 19 of 42 samples collected in Virginia. Half of the Virginia samples were collected because they were mold-damaged. Zearalenone levels ranged from 0.36 to 11.05 ppm; the identity of the zearalenone was confirmed by gas-liquid chromatography and mass spectroscopy. Gibberella zea infection (6-60%) was detected in all of the zearalenone-positive samples; 6-60% of the kernels in the samples tested contained G. zea.  相似文献   

20.
The aim of this study was to determine the relationship between the oxidative and reductive metabolic pathways of acrylamide (AA) in the nonsmoking general population. For the first time both the blood protein adducts and the urinary metabolites of AA and glycidamide (GA) were quantified in an especially designed study group with even distribution of age and gender. The hemoglobin adducts N-carbamoylethylvaline (AAVal) and N-( R, S)-2-hydroxy-2-carbamoylethylvaline (GAVal) were detected by GC-MS/MS in all blood samples with median levels of 30 and 34 pmol/g of globin, respectively. Concentrations ranged from 15 to 71 pmol/g of globin for AAVal and from 14 to 66 pmol/g of globin for GAVal. The ratio GAVal/AAVal was 0.4-2.7 (median = 1.1). The urinary metabolites were determined by LC-MS/MS. Of all urine samples examined 99% of N-acetyl- S-(2-carbamoylethyl)- l-cysteine (AAMA) levels and 73% of N-( R/ S)-acetyl- S-(2-carbamoyl-2-hydroxyethyl)- l-cysteine (GAMA) levels were above the LOD (1.5 microg/L). Concentrations ranged from 相似文献   

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