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1.
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2.
A micellar electrokinetic capillary chromatography (MECC) mode was applied to a capillary electrophoresis (CE) method, which was developed for detection and quantitation of patulin in apple ciders. This method used a small sample amount (2 mL) and consumed minimal organic solvent compared to the most commonly used HPLC methods. The sample preparation procedure of the CE method was also simpler than other chromatographic techniques developed for patulin analysis. Patulin was detected with a photodiode array detector at 273 nm. The standard curve was linear (r(2) = 0.9984) from 75 microgram/L to 121 microgram/mL with patulin working solutions corresponding to 3.8 microgram/L to 6.1 microgram/mL patulin in the sample. The linearity was better in a narrower range of concentrations (r(2) = 0.9999) from 75 microgram/L to 24.1 microgram/mL. The limit of detection of the method was 3.8 microgram/L. Patulin recoveries at 4 levels in spiked samples (10-121 microgram/L) ranged from 95.2 to 105.4%. The recoveries were 96. 9% and 99.2% for 2 levels (22.3 and 223 microgram/L, respectively) of patulin in infected apple samples. This method represents a unique alternative method for rapid and sensitive analysis of patulin in apple ciders.  相似文献   

3.
Net protein ratio data: AACC-ASTM collaborative study   总被引：1，自引：0，他引：1  
Seven- and 14-day net protein ratio (NPR) data were obtained from 7 laboratories for 6 protein sources: ANRC casein, lean beef, lactalbumin, textured vegetable protein, and peanut flour were fed as 10% protein (N X 6.25) in the test diet. Wheat flour, casein, and textured vegetable protein were fed as 6% protein (N X 6.25) in the test diet. Weighed dry ingredients for each diet were sent to each collaborator , who mixed the dry ingredients, then added specified amounts of corn oil and water and mixed each complete diet thoroughly. Rats were adapted for 0, 2, or 4 days, and then were fed the test diets for 28 days for protein efficiency ratio (PER) diets. The animal weight gain and feed consumption data obtained after 7 or 14 days of feeding were used to calculate NPR values. Analyses of data were done before [net protein ratio (NPR)] and after (R-NPR [relative-NPR]) adjustment of the data from each laboratory by its results for the reference protein casein. From the analysis of variance for NPR, significant (P less than 0.05) interactions were observed among laboratories, protein sources, and adaptation times of the animals (0, 2, or 4 days). Inter- and intralaboratory variability were decreased by use of 14-day values compared with 7-day values. Adjustment of the NPR data to R-NPR did not lower the intralaboratory variability but did lower the interlaboratory variability of the data. Increasing adaptation time did not consistently decrease interlaboratory or intralaboratory variability or decrease coefficients of variation (CV) of R-NPR values.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
The validity of 2 electrothermal atomic absorption spectrometric methods for determination of selenium in foods and diets was tested. By using 0.5% Ni(II) as a matrix modifier to prevent selenium losses during the ashing step, it was shown that selenium can be determined in samples containing greater than or equal to 1 microgram Se/g dry wt without organic extraction. The mean recovery tested, using NBS Bovine Liver, was 98%; recovery of added inorganic selenium in Bovine Liver matrix was 100%. In addition, this method gave values closest to the median value of all participating laboratories using hydride generation AAS or the spectrofluorometric method in a collaborative study on high selenium wheat, flour, and toast samples. For samples with concentrations less than 1 microgram Se/g dry wt, separation of selenium from interfering Fe and P ions by organic extraction was necessary. Using inorganic 75Se in meat and human milk matrixes, an ammonium pyrrolidine dithiocarbamate-methyl isobutyl ketone-extraction system with added Cu(II) as a matrix modifier yielded the best extraction recoveries, 97 and 98%, respectively. Accuracy and precision of the method were tested using several official and unofficial biological standard materials. The mean accuracy was within 4% of the certified or best values of the standard materials and the day-to-day variation was 9%. The Se/Fe or Se/P interference limits proved to be low enough not to affect selenium determinations in practically all foods or diets. The practical detection limit of the method was 3 ng Se/g dry wt for 1.0 g dry wt samples.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
A tungsten carbide coating on the integrated platform of a transversely heated graphite atomizer was used as a modifier for the direct determination of Se in soil extracts by graphite furnace atomic absorption spectrometry. Diethylenetriaminepentaacetic acid (0.0050 mol L(-1)) plus ammonium hydrogencarbonate (1.0 mol L(-1)) extracted predominantly available inorganic selenate from soil. The formation of a large amount of carbonaceous residue inside the atomizer was avoided with a first pyrolysis step at 600 degrees C assisted by air during 30 s. For 20 microL of soil extracts delivered to the atomizer and calibration by matrix matching, an analytical curve (10.0-100 microgram of L(-1)) with good linear correlation (r = 0.999) between integrated absorbance and analyte concentration was established. The characteristic mass was approximately 63 pg of Se, and the lifetime of the tube was approximately 750 firings. The limit of detection was 1.6 microgram L(-1), and the relative standard deviations (n = 12) were typically <4% for a soil extract containing 50 microgram of L(-1). The accuracy of the determination of Se was checked for soil samples by means of addition/recovery tests. Recovery data of Se added to four enriched soil samples varied from 80 to 90% and indicated an accurate method.  相似文献   

6.
通过配合喷施不同浓度亚硒酸钠（Na2SeO3）和醋酸锌[(CH3COO)2Zn·2H2O],研究硒（Se）、锌（Zn）及硒锌交互（Se-Zn）作用对夏茶叶片多酚氧化酶（PPO）活性的影响。结果表明,单施Se（100~200 μg/mL）和单施 Zn（0.4%~0.8%）处理,茶叶叶片PPO活性相对较高;高浓度Se（400 μg/mL）和 Zn（1.2%）处理对PPO活性的提高效应不明显,甚至有一定的抑制作用。同一Se、Zn处理喷施16 d后,茶叶叶片PPO活性相对较高。中浓度Zn（0.4%~0.8%）与中浓度Se（100~200 μg/mL）配合喷施,夏茶叶片多酚氧化酶活性较高;而高浓度的硒锌配施对PPO活性无明显促进效应。同一配施处理,喷施16 d后PPO活性变化趋于稳定,且比喷施8d活性增幅较大。高浓度的Zn与不同浓度的Se配施,PPO活性的时间效应不甚明显,而低中浓度Zn与不同浓度Se配合喷施后,PPO活性的时间效应明显。  相似文献   

7.
Methods of analysis prescribed by USSR standards for Hg, Pb, Zn, As, Cd, Cu, Fe, and Sn in foods are described: for Hg--colorimetry of tetraiodide mercurate and atomic absorption spectroscopy (AAS); for Pb, Cd, Zn, and Cu--polarography; for Cu--colorimetry with sodium diethyldithiocarbamate and zinc dibenzyldithiocarbamate; for As--colorimetry with silver diethyldithiocarbamate; for Sn--colorimetry with quercetin; and for Fe--colorimetry with o-phenanthroline. All of the methods have the necessary metrological characteristics, including intralaboratory repeatability value (r), interlaboratory reproducibility value (R), minimum quantity of the element to be determined in the analytical test portion (MQSM), and the coefficients that account for mercury and arsenic losses during analysis. Establishing constant r- and R-values for the methods under consideration is expedient because (a) the methods suggested are used for safety purposes; and (b) the optimum amount of the element studied in the test sample is determined, to a certain degree, by the mass of the test portion.  相似文献   

8.
The microtiter plate system for turbidimetric assay of chlortetracycline (CTC) and oxytetracycline (OTC) levels in feeds uses a 96 well microtiter plate, a multichannel pipette, and an ELISA reader to measure turbidity. Feeds are extracted for both tetracyclines using AOAC extraction systems. For CTC, the range of the standard curve is 0.001-0.005 microgram CTC/mL; for OTC, the range is 0.004-0.016 microgram OTC/mL. Repeatability of CTC assays, as shown by the coefficient of variation (CV), ranged from 0.54 to 5.65% for same-day assays and from 2.01 to 9.39% for assays on different days. For OTC, CVs ranged from 2.69 to 10.01% for same-day assays and 3.24 to 9.08% for different-day assays. Average recoveries for CTC were 108.7% for same-day assays and 106.8% for different-day assays; for OTC, average recoveries were 112.4% and 106.5% for same-day and different-day assays, respectively.  相似文献   

9.
The present study was conducted in a 2 x 4 factorial arrangement in a randomized complete block (RCB) design to compare the effects of a commercial inorganic Se source (sodium selenite, SS) with a commercial organic Se source (Se-enriched yeast, SY) on tissue Se distribution and blood and whole-egg Se concentrations in laying hens. Both Se sources were added into the basal diet at 0, 0.2, 0.5, and 1.0 mg/kg of Se. Seven hundred 68 week old Rohman laying hens were fed with a basal diet containing 0.15 mg/kg DM (dry matter) of Se for 2 weeks, and then, they were allocated randomly into seven groups and were investigated for 28 days. Each group was replicated five times with five cages of four hens per cage in each replicate. During the experiment, two eggs per replicate from each treatment were collected every 7 days and blood was sampled on days 0, 14, and 28 for whole-egg and whole-blood Se analyses. At the end of the experiment, two hens per replicate from each treatment were slaughtered, and muscle (cardiac and breast muscles), liver, spleen, and kidney were sampled for the determination of Se concentrations. The results showed that the addition of Se from either source caused a significant increase in whole-egg and whole-blood Se concentrations (p < 0.01) and Se concentrations in liver, kidney, spleen, and cardiac and breast muscles (p < 0.05) of hens in comparison to the control. Both Se sources and Se levels significantly influenced (p < 0.01) Se concentrations in egg, blood, and the above-mentioned tissues. There was a more significant increase in the Se concentrations in egg (p < 0.01), spleen (p < 0.05), and breast muscle (p < 0.01) and a decrease (p < 0.01) in whole-blood and kidney from hens fed SY than those from hens fed SS. The order of Se distribution was liver > kidney > spleen > cardiac muscle > egg > blood > breast muscle, irrespective of the addition level or source. It was concluded that meat and eggs from hens fed commercial SY are a potential source of Se for humans.  相似文献   

10.
Eleven collaborating laboratories conducted replicate analyses on 4 blind duplicate pairs of bovine liver samples that either had naturally acquired copper levels or were spiked with one of 3 copper levels. A National Bureau of Standards Bovine Liver sample (SRM 1577, 193 +/- 10 mg copper/kg) and a 1000 mg copper/L standard were also submitted to the collaborators. The method requires the tissue to be digested with concentrated HNO3 at 60 degrees C, diluted to volume with water, and analyzed by atomic absorption spectrophotometry. The intralaboratory coefficients of variation (CVo) ranged from 5.6 to 19%; the interlaboratory CVx values ranged from 7.1 to 21%. The lower limit of detection was estimated to be 1 mg copper/kg tissue. The method has been adopted official first action.  相似文献   

11.
Total selenium is determined by inductively coupled plasma (ICP) atomic emission using hydride vapor generation. A 1 g sample is wet ashed in a 16 x 150 mm 10 mL volumetric test tube on a programmed heating block with nitric, sulfuric, and perchloric acids at up to 310 degrees C. After treatment with hydrochloric acid, the selenium is reduced by sodium borohydride to hydrogen selenide is a simplified continuous flow manifold. A standard pneumatic nebulizer effects the gas-liquid separation of H2Se, which is quantified by ICP atomic emission at 196.090 nm. The instrument detection limit for the method has been determined to be 0.4 microgram/L. For a 10:1 dilution of a nominal 1 g sample, the detection limit is 4 micrograms/kg and the linear range is up to 4 mg/kg. The method has demonstrated statistical control for samples of biological and environmental interest and is especially well suited to analysis of small samples.  相似文献   

12.
A new liquid chromatographic method for determination of ampicillin in canine and equine serum has been developed. The serum sample (500 microL) is vortex-mixed with 20% ethanol (500 microL) and filtered using a 30,000 molecular weight cutoff microseparation tube to separate high molecular weight solutes following low-speed centrifugation. Ampicillin is then separated from other serum components by reverse phase ion-pair liquid chromatography (LC). The ultraviolet (UV) absorbance of the column effluent is monitored at 230 nm. Recoveries of ampicillin from canine serum spiked at concentrations of 10, 40, and 60 micrograms/mL were 93.1, 100.9, and 87.8%, respectively, with coefficients of variation (CVs) of 2.91, 3.08, and 4.08%, respectively. Recoveries of ampicillin from equine serum spiked at the same concentrations were 91.6, 90.1, and 88.7%, respectively, with CVs of 3.03, 2.61, and 3.35%, respectively. The limit of detection for ampicillin by this method is less than 0.5 micrograms/mL serum.  相似文献   

13.
Typical volatile heterocyclic compounds found in brewed coffee extracts-pyrroles, furans, thiophenes, and thiazoles-were examined for antioxidative activity, which was determined by measuring the oxidative conversion of hexanal to hexanoic acid using gas chromatography. 2-Acetylpyrrole, 1-methylpyrrole, and pyrrole inhibited hexanal oxidation by 98, 87, and 78%, respectively, at a concentration of 500 microgram/mL over a period of 30 days. 2-Methylfuran, which inhibited hexanal oxidation by 90% at all concentrations tested (500, 200, and 100 microgram/mL) for a 30-day period, exhibited the greatest activity among furans tested. Similarly, 2-methylthiophene, which inhibited hexanal oxidation by almost 100% at a concentration of 500 microgram/mL over 30 days, exhibited the greatest activity among the thiophenes tested. In general, thiazoles were ineffective antioxidants at all concentrations tested. However, 4,5-dimethylthiazole was able to inhibit hexanal oxidation by 50% at the highest level tested (500 microgram/mL). 2-Acetylpyrrole, 2-methylfuran, and 2-methylthiophene at concentrations of 500, 200, and 100 microgram/mL and furan at a concentration of 500 microgram/mL exhibited antioxidative activities comparable to that of the synthetic antioxidant butylated hydroxytoluene at a concentration of 50 microgram/mL.  相似文献   

14.
Growing selenium (Se)-biofortified alternative crops in saline and Se-contaminated agricultural land in arid/semi-arid regions, such as the western United States, depends upon the plant’s ability to tolerate high salinity and accumulate Se. In this field study, we evaluated the ability of five prickly pear cactus clones [Opuntia ficus-indica (L.) Mill., no. 243, 248, 250, 252, and 255] to grow, accumulate and volatilize Se from drainage sediment high in sulphate salinity (∼5 dS/m), soluble B (∼5 mg/L) and Se concentrations (∼0.8 mg/L). After 3 years of growth, all clones exhibited significant decreases up to 20% in height and fruit production compared with control clones. Mean Se concentrations (mg/kg DM) ranged from 4.9 to 9.8 in cladodes, 1.5–2.5 in fruit flesh, and 4.5–10.1 in seeds. Rates of Se volatilization varied from 20 to 80 μg Se/m2 per day among the tested clones. The successful growth of prickly pear cactus and its accumulation and volatilization of Se under adverse soil conditions may provide growers with an alternative Se-biofortified crop in the westside of the San Joaquin Valley in central California.  相似文献   

15.
In some regions of the world, where the bioavailability of selenium (Se) in soil is low and/or declining (e.g., due to use of high-sulfur fertilizers), there is increased risk of adverse affects on animals and human health. In recent years, increased research attention has focused on understanding the relationships between Se contents in foods and supplements and their nutritional benefits for animal and humans. The objective of this study was to use a species-unspecific isotope dilution and reverse phase ion pairing-inductively coupled plasma-mass spectrometry techniques for the identification and quantification of Se species in biofortified grains (i.e., wheat and triticale), flour, and wheat biscuits. The information on Se species was used to gain an understanding of the bioavailability of Se in biofortified and process-fortified wheat biscuits used in a clinical trail. The major Se species identified in biofortified and process-fortified samples were selenomethionine (76-85%) and selenomethionine selenoxide (51-60%), respectively. Total plasma Se concentrations in the biofortified Se exposure group were found to increase throughout the 6 month trial period (mean=122 microg L(-1) at 0 months to 194 microg L(-1) at 6 months). In contrast, the trial group exposed to process-fortified Se biscuits showed little increase in mean total Se plasma concentrations until 4 months of exposure (mean=122 microg L(-1) at 0 months to 140 microg L(-1) at 4 months) that remained constant until the end of the trial period (mean=140 microg L(-1) at 4 months to 138 microg L(-1) at 6 months). The difference in total Se plasma concentrations may be due to the presence and bioavailability of different Se species in biofortified and process-fortified biscuits. An understanding of Se speciation in foods enables better understanding of pathways and their potential benefits for animals and humans.  相似文献   

16.
A simple procedure based on solid-phase extraction and high performance liquid chromatography coupled to diode array detector has been developed and validated for the qualitative and quantitative analysis of cis- and trans-resveratrol in wines. The method was linear from 0.025 (lower limit of quantitation, LLOQ) to 15 μg/mL for trans-resveratrol and from 0.023 (LLOQ) to 0.92 μg/mL for cis-resveratrol, with correlation coefficients higher than 0.99 for both isomers. Intra- and interday precision and accuracy were in conformity with the criteria normally accepted in method validation, that is, CVs inferior to 15% and mean relative errors within a ±14% interval. The extraction presented mean efficiencies close to 100% for both analytes. The validated methodology was applied to 186 Portuguese red wines from different regions, grape varieties and vintage. The results obtained showed that the content of trans-resveratrol in red wines ranged from 0.05 to 10.9 μg/mL, while the concentrations of cis-resveratrol ranged from 0.04 to 8.71 μg/mL.  相似文献   

17.
A method is presented for determining molybdenum in plant tissue and blood plasma by flame and flameless atomic absorption spectroscopy (AAS). The samples are digested with HNO3-HCIO4, and the metal is separated by chelation, extracted into methyl isobutyl ketone, and analyzed by AAS. Recoveries of molybdenum from fortified samples ranged from 92.0 to 98.9%. The limits of detection on the flame and graphite furnace were 10 and 2 ng/mL, respectively.  相似文献   

18.
Microbial reduction of selenate [Se(VI)] to elemental selenium [Se(0)] is a useful technique for removing Se from agricultural drainage water. A series of batch experiments were conducted in the laboratory to determine the effects of yeast extract (50-1000 mg/L), salinity (EC, 5-75 dS/m), and NO(3)(-) (5-100 mg/L) on the removal of Se(VI) (2000 microg/L) from drainage water by Enterobacter taylorae. Results showed that relatively high amounts of yeast extract (500 mg/L) were needed for E. taylorae to effectively reduce Se(VI) to Se(0). During a 7-day experiment, approximately 95% of added Se(VI) was reduced to Se(0) in the low-salinity drainage water (5 dS/m) with NO(3)(-) values of 5-50 mg/L. In the high-salinity drainage water (50-75 dS/m), reduction of Se(VI) to Se(0) was limited. E. taylorae was also capable of reducing Se(VI) to Se(0) in the San Joaquin Valley drainage water, with a reduction of the added Se(VI) to Se(0) (73.8%) and Se(-II) (20%). This study suggests that E. taylorae may be used to treat Se(VI)-contaminated drainage water in the field.  相似文献   

19.
Beef provides a significant portion of human dietary selenium (Se), and it is possible that modest portions of beef produced in areas with high-Se soil and forage could provide the entire Recommended Dietary Allowance (RDA) for Se. The present study has addressed the environmental conditions that resulted in the production of high-Se beef. One hundred and thirty-eight cull cows were obtained from 21 ranches in five distinct geographic regions that, on the basis of soil parent material, reports of Se deficiency, and previous soil and forage Se surveys, were likely to have high or low Se concentrations in the soil. Grass and soil samples were taken from ranch sites, and hair, whole blood, skeletal muscle, diaphragm muscle, and liver samples were obtained from the animals. Hair and whole blood samples were taken 1 day prior to shipping. Selenium concentrations of all samples were determined by hydride generation atomic absorption spectroscopy. Geographic origin affected Se content of all samples (p < 0.05). Selenium concentrations in soil (r = 0.53; p < 0.01) and grass (r = 0.63; p < 0.01) were correlated to Se content of skeletal muscle. Selenium concentrations in whole blood, diaphragm, hair, and liver also were significantly correlated to Se content of skeletal muscle (p < 0.01). Cows that received Se in mineral supplements did not have significantly higher concentrations of Se in sampled tissues (p > 0.05). Results of this study suggest that the greatest source of variation in Se content of bovine skeletal muscle was the geographic region from which the beef originated and not production or management practices. Results also demonstrated that a 100 g serving of high-Se beef could provide 100% of the RDA for Se.  相似文献   

20.
杜倩  王昌全  李冰  李焕秀  刘杨 《核农学报》2010,24(1):118-124
通过喷施不同浓度的亚硒酸钠和醋酸锌,研究了硒、锌及硒锌交互作用对不同季节茶叶叶片硒、锌含量以及多酚氧化酶活性的影响。结果表明:(1)茶叶硒、锌含量均在春季最高,夏季次之,秋季最低。3季茶叶硒含量都在中高浓度(200~400μg/ml)的硒和低中浓度(0.2%~0.4%)的锌处理下相对较高;而锌含量在中高浓度(0.8%~1.2%)的锌和低中浓度(50~100μg/ml)的硒处理下较高;各季节茶叶硒、锌含量都在中浓度的硒(100~200μg/ml)和锌(0.4%~0.8%)配比下较高。(2)茶叶多酚氧化酶活性在夏季最高,春季次之,秋季最低。3季茶叶该酶活性均在中浓度的硒(100~200μg/ml)和锌(0.4%~0.8%)处理及其配比下相对较高;而高浓度的硒(400μg/ml)和锌(1.2%),以及低浓度(0.2%)的锌处理对春茶和夏茶多酚氧化酶活性的提高效应不甚明显,秋茶多酚氧化酶活性则在低浓度的硒(50μg/ml)和低浓度的锌(0.2%)以及高浓度的硒(400μg/ml)、锌(1.2%)处理下均无明显提高效应,同时低硒与低锌配比、高硒与中高浓度(0.2%~0.8%)的锌配比对春、夏、秋3季茶叶PPO活性的促进效应均不明显。  相似文献   

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