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1.
A collaborative study of the determination of mercury in fish has been completed in which wet oxidation of fish tissue in nitric acid, using vanadium as a catalyst, is compared with the AOAC official final action digestion technique, 25.103-25.105, involving a nitric-perchloric acid mixture. The study used tuna fish samples of known mercury content and included spike recovery studies in which methyl mercury solutions of known composition were provided to each laboratory. The study was designed to provide recovery information that bracketed the regulatory level of mercury in fish. The results indicate that the proposed digestion method is at least as precise and accurate as the AOAC method. The proposed method is also more rapid and less hazardous. It has been adopted as official first action.  相似文献   

2.
A modification of the official AOAC method for determining methyl mercury in fish and shellfish was studied in 8 laboratories. Methyl mercury is isolated from homogenized, acetone-washed tissue by adding HCl and extracting into toluene the methyl mercuric chloride produced. The extract is analyzed for methyl mercuric chloride by electron capture gas chromatography. Collaborators determined methyl mercury in blind duplicate homogenates at 2 levels in tuna and at 1 level in swordfish and oysters. Collaborators also analyzed single homogenates of swordfish and oysters containing methyl mercury at a second level. Both fortified and unfortified tissues were analyzed. Methyl-bound mercury in the commodities ranged from 0.50 to 2.30 micrograms Hg/g. Reproducibility coefficients of variation ranged from 4 to 15%. Accuracy, measured by comparison to reference values, ranged from 92 to 101%. Recovery from fortified homogenates ranged from 86 to 98%. Reference values and unfortified levels were determined in the author's laboratory by replicate analysis of fortified and unfortified commodities. The method has been approved interim official first action.  相似文献   

3.
Ground-level concentrations of three atmospheric mercury species were measured using manual sampling and analysis to provide data for estimates of mercury dry deposition. Three monitoring stations were operated simultaneously during winter, spring, and summer 2004, adjacent to three mercury wet-deposition monitoring stations in northern, central, and southern Indiana. The monitoring locations differed in land-use setting and annual mercury-emissions level from nearby sources. A timer-controlled air-sampling system that contained a three-part sampling train was used to isolate reactive gaseous mercury, particulate-bound mercury, and elemental mercury. The sampling trains were exchanged every 6 days, and the mercury species were quantified in a laboratory. A quality-assurance study indicated the sampling trains could be held at least 120 h without a significant change in reactive gaseous or particulate-bound mercury concentrations. The manual sampling method was able to provide valid mercury concentrations in 90 to 95% of samples. Statistical differences in mercury concentrations were observed during the project. Concentrations of reactive gaseous and elemental mercury were higher in the daytime samples than in the nighttime samples. Concentrations of reactive gaseous mercury were higher in winter than in summer and were highest at the urban monitoring location. The results of this case study indicated manual sampling and analysis could be a reliable method for measurement of atmospheric mercury species and has the capability for supplying representative concentrations in an effective manner from a long-term deposition-monitoring network.  相似文献   

4.
The use of purge and trap gas chromatography–mass spectrometry (GC-MS) technique for the determination of methylmercury in biological and sediment samples was described. The GC-MS detection system was combined with the dithizone extraction method for biological samples and the distillation method for sediment samples to alleviate matrix interference problems. The method was validated by analysis of CRMs such as SRM 966 (human blood), BCR 463 (tuna fish), IAEA 407 (fish), ERM CC580 (estuarine sediment), and IAEA 405 (sediment). The performance of the purge and trap GC-MS method was also tested on field samples of freshwater fish and sediment. The results were compared with those of the GC-ECD and the GC-CVAFS, which were used widely for methylmercury analysis. Additionally, total mercury and methylmercury levels in freshwater fish and sediments from various reservoirs and streams in Korea were measured to understand mercury contamination status in Korean peninsula. Methylmercury concentrations in freshwater fish were found to correlate with body weight, diet habit, and food availability. In sediment, total mercury concentrations correlated with methylmercury concentrations and organic matter such as %C and %S. However, no significant relationships between methylmercury and sediment organic matter have been found.  相似文献   

5.
A simple and rapid procedure for measuring total mercury in fishtissues is evaluated and compared with conventional techniques.Using an automated instrument incorporating combustion, preconcentration by amalgamation with gold, and atomic absorptionspectrometry (AAS), milligram quantities of wet fish tissue wereanalyzed directly for mercury (i.e., without acid digestion). Seven tissue types (skeletal muscle, liver, blood, gonad, brain, gill, and heart) from five species (340 fish) were analyzed. Because of the small quantities of tissue needed for analysis, wedocument the homogeneity of mercury within the tissues and determine a preferred sampling technique and location for skeletal muscle. The precision was found to be generally > 10% (rsd), and the accuracy was determined by using certified reference materials (dogfish muscle, dogfish liver, and oystertissue). Comparisons to conventional cold-vapor AAS (CV-AAS) andisotope dilution inductively coupled plasma mass spectrometry found that the methods give statistically equivalent (p > 0.05) results. Because the combustion-AAS method is faster than conventional CV-AAS and produces no waste reagents, it should be particularly useful for laboratories that analyze large numbers of fish for mercury. The method detection limit for fish-muscle homogenate was estimated at 0.9 ng g-1.  相似文献   

6.
The objective of this study was to determine the efficiency of a portable total mercury analyzer (OhioLumex RA-915+) in comparison with traditional analytical methods, such as inductively coupled plasma atomic emission spectrometry and cold vapor atomic absorption. The quick mercury analytical procedure with the direct mercury analyzer without sample pretreatment (such as sample digestion) was optimized for a variety of environmental samples, including contaminated soil and plant samples. The efficiency was evaluated using practical parameters, such as time required for analysis, sample amount, mercury species, accuracy, and precision/reproducibility, as well as using statistical analysis. Our results demonstrate that these three instrumental methods yielded similar mercury concentration values and statistical data, while the mercury direct analyzer had the advantages of not requiring for sample digestion and only requiring a small quantity of samples for distribution of mercury in a single root, a single root hair, and sub-regions of a single leaf of plants. These factors are used to justify use of the portable direct mercury analyzer under field conditions and validation of the results.  相似文献   

7.
自然源汞释放对全球大气汞的贡献和循环具有重要影响,地表过程释汞是大气汞重要的自然源,土壤空气汞浓度与大气汞浓度差决定着土壤/大气汞的交换通量。基于目前测定土壤空气中汞浓度的缺点,建立了一种新的测定土壤空气汞浓度的方法。本研究在南京六合循环农业生态区采集了水稻土壤剖面空气,并对样品总汞浓度进行了分析。利用本实验装置,真空泵在低流量下连续抽取土壤剖面空气并预富集于金管上,并结合冷原子荧光法(CVAFS)测定。实验结果显示方法检出限为0.023 ng m-3,水稻土壤空气汞浓度变化范围在6.0~18.9 ng m-3。平行实验装置在同时测定实验室大气和农田土壤空气汞浓度时,相对标准偏差(RSD)均小于15%,同时对比实验证明没有采集土壤表层大气。实验装置简单,野外操作方便,能准确和精确的测定水分不饱和土壤空气中汞浓度。  相似文献   

8.
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9.
The official first action AOAC gravimetric method for mercury, 6.C01-6.C03, and the official CIPAC titrimetric method, M2.3, were collaboratively studied by 4 CIPAC laboratories, using the same 4 samples analyzed by AOAC collaboration in 1972. Averages at the 3.7 and 3.4% level were the same by both methods whereas the CIPAC method produced, on the average, 4% higher results, all levels included. The AOAC method performs well in the presence of copper and chlorinated pesticides and is less complex to use than the present CIPAC method for mercury in these mixtures. The method has been adopted as official final action.  相似文献   

10.
原位现场γ谱仪具有快速准确监测土壤中环境放射性核素137Cs和210Pbex的潜力,可以解决传统环境放射性核素示踪土壤侵蚀在选择参考点和测定时间过长问题。本研究应用现场γ谱仪(ISOCS,In-situObject Counting System),对内蒙古锡林浩特草原土壤中137Cs和210Pbex的含量进行了田间原位(不采样)测定,并与室内γ谱仪测定结果进行了比对。结果显示:现场γ谱仪的探头离地面1m,采用90度准直器,测量时间保证3600s以上时,测定的土壤中137Cs面积浓度与室内测定结果一致,二者的平均偏差为8%,表明现场γ谱仪测定具有较高精度,是快速评价土壤侵蚀速率的有效技术;210Pbex的原位测定结果显著高于室内测定结果,可能由于测定时间较短所致。初步研究结果表明:原位测定具有时间短、精度高的优点,可以克服传统采样造成的空间变异误差。  相似文献   

11.
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12.
A previously developed method that uses a simplified sample preparation procedure and atomic absorption detection of liquid chromatographic eluates for the determination of methyl mercury in seafood has been collaboratively studied. The unique feature of the method involves the use of a specially designed interface for the generation of mercury vapor. Methyl mercury is isolated from the blended sample by chloroform elution from a diatomaceous earth-hydrochloric acid column. The organomercury compound is then extracted into a small volume of 0.01M sodium thiosulfate solution. An aliquot of this solution is injected onto a Zorbax ODS column and eluted with methanol-ammonium acetate solution (3 + 2), pH 5.7, containing 0.01% mercaptoethanol. Mercury is detected by flameless atomic absorption spectrophotometry using the interface. The samples analyzed in the study were unspiked swordfish, unspiked and spiked lobster, and unspiked and spiked tuna. The spiked samples contained methyl mercury both above and below the U.S. Food and Drug Administration guideline level of 1 microgram Hg/g. Reproducibility relative standard deviations ranged from 10.5% at 1 microgram Hg/g to 18.2% at about 0.1 microgram Hg/g. Accuracy, measured by comparison to reference values obtained by the Associate Referee, ranged from 94.4 to 99.6%. The method has been adopted official first action.  相似文献   

13.
Chemical speciation of mercury (Hg) in a wide variety of combustion flue gas matrices has been determined using the mercury speciation adsorption (MESA) method. The MESA sampling system for gas phase Hg species employs a series of heated, solid phase adsorbent traps. Flue gas oxidized Hg species (Hg(II) and MMHg) are adsorbed by a potassium chloride (KCl) impregnated soda lime sorbent. Elemental Hg (Hg0) is collected by an iodated carbon sorbent after passing through the KCl/soda lime sorbent. Total Hg (Hgt) is determined by summation of species. In the laboratory, cold vapor atomic fluorescence spectroscopy (CVAFS) is used for detection of Hg collected on the solid sorbents, after appropriate sample digestion and preparation. The MESA method has been evaluated for species stability, matrix effects, breakthrough, artifacts and precision. Based on eight duplicate samples a mean precision of 6.8% 11% and 4.5% (relative percent difference) has been calculated for Hg0, Hg(II) and Hgt respectively. Intercomparison of the MESA method with other methods shows very good agreement for Hgt. Mass balance calculations at 5 sites range from 75 to 140%, with a mean of 97±25%. Overall mean speciation results from 19 separate determinations suggest that Hg(II) has a 1 sigma range of 40 to 94% in coal combustion flue gas at, the inlet to pollution control devices.  相似文献   

14.
Togwa is a starch-saccharified nonalcoholic traditional beverage consumed in sub-Saharan Africa. In the southern part of Tanzania, togwa is usually made from maize flour and finger millet malt. In this region, togwa is consumed by working people and also used as a refreshment as well as a weaning food. Togwa was prepared in the laboratory using a specific reactor and analyzed for its general chemical composition in both laboratory and field forms. From the analysis of the trace elements and amino acid contents in togwa and its materials, it has been clarified that togwa contains many kinds and a high quantity of minerals derived from finger millet malt. It was concluded that togwa should be nourishment and a major source of minerals as nutrients for the inhabitants of this region.  相似文献   

15.
This paper is an extensive review of the research that has been undertaken on near-infrared (NIR) and mid-infrared (MIR) spectroscopy applied to soil particularly for determining carbon (C) content. The objective is to determine which acquisition method (NIR, MIR, in the field or in the laboratory) might be recommended for the purpose of C stock measurement with a particular interest in carbon credit trading. For this purpose, an optimal method has to satisfy the dual constraints of low-cost and high throughput analysis. The various methods proposed in the literature are compared. In order to make comparisons as reliable as possible, special attention has been paid to the conditions of data acquisition (sample preparation), and to calibration and validation procedures. In particular, whether the validation has been carried out on fully independent samples or on samples similar to the ones of the calibration set greatly influences the results. Also, for C stock measurement, it is absolutely necessary to measure the bias of the prediction in order to be conclusive about the feasibility of the method. However, only few researchers provide this parameter and we recommend including it as a matter of course in future reports. Finally, although MIR on dried and ground samples is the most accurate method, on-the-go and in-field sensors provide predictions accurate enough to show promise in being a valuable component of technologies that would be used for C-credit purposes. But in order to meet the cost/accuracy trade-off, the main issue using such field sensors is to be able to simultaneously measure the bulk density or, better, to directly measure the volumetric concentration of C in soil. This circumvents the costs of field extraction and laboratory analysis. This is the next great challenge to be met by soil scientists.  相似文献   

16.
Butyryl cholinesterase of different origin along with variations of the time of enzyme immobilization on the potentiometric transducer surface is offered to control the ion sensitive field effect transistor (ISFET)-based biosensor sensitivity. Because butyryl cholinesterase has been already used to develop the sensors for heavy metals, organophosphorus/carbamate pesticides, and steroidal glycoalkaloids analysis, the present study has been focused on the investigation and adjustment of the ISFET-based biosensor specificity exclusively to the glycoalkaloids. Utilization of ethylendiaminetetracetate (a complexon of heavy metal ions) and phosphotriesterase (a highly efficient catalyst for the hydrolysis of organophosphorus compounds) enabled the highly specific determination of glycoalkaloids at the background of lead and mercury (up to 500 microM of ions concentration) and paraoxon (up to 100 microM of pesticide concentration). The developed biosensor has been validated for glycoalkaloids detection in potato varieties cultivated in Ukraine, and the results obtained are compared to those measured by the methods of HPLC and TLC.  相似文献   

17.
A method consisting of digesting animal feeds in a block digestor and determining ammonia by steam distillation followed by titration has been evaluated and compared with the official final action Kjeldahl method, 7.016. Fifteen laboratories analyzed 5 feed samples and lysine monohydrochloride. Statistical analysis showed that results from the 2 methods were comparable. The distillation technique has been adopted as official first action as an alternative technique for ammonia determination from the digest of the official final action block digestor method, 7.B11.  相似文献   

18.
土壤养分状况系统研究法应用美国国际农化中心的ASI联合浸提液(0.25mol/L NaHCO3-0.01mol/L EDTA-0.01mol/L NH4F)测定土壤中11种大、中、微量元素含量,结合土壤对营养元素的吸附研究和盆栽试验,判断土壤中存在的和潜在的养分限制因子,用以指导田间试验和施肥推荐。在全围17个省(市、自治区)范围内选取了140个土壤样品,应用该方法对土壤养分状况进行了研究。盆栽试验结果表明,土壤中氮、磷、钾、锌、硫、铜、硼、锰、钼、镁、钙和铁成为限制因子的土壤分别为137、126、84、68、45、37、36、34、28、25、20和17个。应用Cate和Nelson的方法估计出11种元素(钼除外)测定值在盆栽条件下的临界值。 应用在原取土地块安排的田间试验的资料估计出大田条件下应用ASI联合浸提液测定的土壤磷、钾含量的临界值分别为15mg/L和90mg/L。应用河北省玉田县试验和示范资料建立的计算机测土施肥模型综合考虑了土壤中各种营养元素的综合平衡和土壤对磷、钾的吸附固定能力。  相似文献   

19.
Abstract

A reliable method to rapidly assess the potassium (K) status of alfalfa (Medicago sativa L.) would enhance the ability of producers and crop consultants to make timely decisions regarding K fertilization. Recently introduced to the agricultural market are portable, hand‐held, ion‐specific electrodes, that allow direct measurement of K in plant sap. The objective of this study was to compare the potassium ion‐specific electrode (KSE) meter to flame photometry as a tool to estimate the K status of alfalfa. A total of 75 fields in the low deserts of California and Arizona were sampled in June and again in November‐December of 1995. Seventy‐five mid‐stems from each field were collected and chopped into 1 cm pieces. Sap was extracted from half the sample and analyzed for K concentration with the KSE meter. Sap readings were taken either immediately in the field (method 1) or after transport to the laboratory (method 2). The other half of the sample was oven dried at 60°C and analyzed for K concentration via flame photometry. Sap K concentration by method 1 was well correlated (r2=0.68) with flame photometry; field pressed, but laboratory analyzed samples (method 2) were not as well correlated. In conclusion, the KSE meter could be used as a quick and inexpensive tool to monitor the K concentration of alfalfa mid‐stems if samples are extracted and read immediately in the field.  相似文献   

20.
Species-specific DNA-based tags are valuable tools for the management of both fisheries and commercial fish products. Eleven hake species of the genus Merluccius have been identified employing mtSNPs-based methodology. The method is highly reproducible, fast, and technically easy. It is a reliable tool, allowing for routine analysis of commercial seafood. It can be applied by nonexperts in genetics because both laboratory handling and interpretation of results are easy and direct. The convenience of routine surveys in fish markets has been clearly established with a survey of commercial hake batches imported in south Europe. A total of 40 commercial processed hake were analyzed in this study. More than 20% of mislabeling has been detected.  相似文献   

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