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991.
The 4-mercapto-4-methylpentan-2-one (4MMP) is a key aroma compound in wines, especially in Sauvignon Blanc ones. Its accurate quantification is quite difficult due to its traces levels and its reactivity in wine conferred by the thiol function. In this paper, we proposed a new method for its quantification in wine without any sample preparation, based on automated derivatization procedure by methoximation and SIDA–SPME–GC–MS/MS analysis. The derivatization procedure was adapted from a previously published method in order to decrease the amount of reagents and the volume of wine (only 3 mL are required). The use of SPME and the detection conditions have also been optimized to reach the best sensitivity as possible. The method was then validated according to the International Organization of Vine and Wine recommendations and exhibited excellent performances. Indeed, this method allowed us to quantify the 4MMP in wine at traces levels (LOD = 0.19 ng L−1) with reproducible results (RSD < 15%) and a very good accuracy (recovery = 102%). 相似文献
992.
Kazuo Furihata Jing Zhang Masanori Koda Takuya Miyakawa Masaru Tanokura 《Magnetic resonance in chemistry : MRC》2014,52(7):333-338
NMR analysis of foods frequently suffers from a problem of dynamic range, which limits the detection of minor components due to the huge signals of water and major components such as sugars. In the present study, we propose a new method named as ‘broadband WET’. This pulse scheme was applied to persimmon fruit juice for saturating the resonances of water and sugars, which covered a broad bandwidth. In comparison with the conventional solvent suppression methods such as WET and DPFGSE‐WATERGATE, it was shown that broadband WET provided highly selective suppression of resonances covering an extensive bandwidth and quantitative signals of minor components without distortion. The proposed method is suitable to detect quantitative signals of the minor components with a high sensitivity. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
993.
A sensitive and selective method for the quantitative analysis of miglitol in rat plasma using unique solid‐phase extraction coupled with liquid chromatography–tandem mass spectrometry 下载免费PDF全文
Akiko Mizuno‐Yasuhira Kohnosuke Kinoshita Shigeji Jingu Jun‐ichi Yamaguchi 《Biomedical chromatography : BMC》2014,28(10):1423-1429
A sensitive, selective and robust liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed for the quantification of miglitol in rat plasma. The sample preparation procedures involved protein precipitation and unique solid‐phase extraction, which efficiently removed sources of ion suppression and column degradation interference present in the plasma. Chromatographic separation was achieved on an amide column using 10 mmol/L CH3COONH4 and CH3CN:CH3OH (90:10, v/v) as the mobile phase under gradient conditions. Detection was performed using tandem mass spectrometry equipped with an electrospray ionization interface in positive ion mode.The selected reaction monitoring transitions for miglitol and a stable isotope‐labeled internal standard were m/z 208 → m/z 146 and m/z 212 → m/z 176, respectively. The correlation coefficients of the calibration curves ranged from 0.9984 to 0.9993 over a concentration range of 0.5–100 ng/mL plasma. The quantification limit of the proposed method was more than 10 times lower than those of previously reported LC‐MS/MS methods. The novel method was successfully validated and applied to a pharmacokinetic study in rats. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
994.
介绍了等精度和不等精度两种测量透镜焦距的方法及相应实验数据的处理,并对两种方法进行了比较。 相似文献
995.
996.
997.
Traceability to the System International (SI) is an important prerequisite for international comparability and uniformity
of chemical measurements to ensure mutual recognition of the results. In theory, all measurements can be traced back to the
seven base units of the SI. Although the traceability system works well for most physical measurements, in many analytical
and in some spectrophotometric measurements this system is not satisfactory. This paper describes the particular and practical
problems and the contribution of the Romanian National Institute of Metrology in this field. The paper discusses the following
concepts: clearly defined targets in the form of requirement specification, knowledge of trueness and/or measurement uncertainty,
and traceability through an unbroken chain of calibration to primary standards. Traceability and uncertainty being two concepts
inherently coupled, two examples of assessment of the uncertainty of measurement results are given for two spectrophotometric
methods currently used in chemical laboratories.
Received: 17 July 1996 Accepted: 2 September 1996 相似文献
998.
通过分析按有效数字定义近似处理标准误差前后引起包含测量结果真值概率的变化,指出现行有效数字概念有一定的局限性,明确了为克服这个局限性,不确定度有时应采取两位数表示。 相似文献
999.
Donald Ludwig 《Natural Resource Modeling》1994,8(2):111-117
After 20 years of effort, technical approaches to natural resource management have not been effective in preventing overuse and destruction of resources. The resource modeling community can help to change our present course toward destruction by (1) recognizing and publicizing the ineffectiveness of scientific, technical and magical approaches to resource management, (2) pointing out that the resolution of environmental problems is impossible unless the social problems of excessive human population sizes and excessive consumption are effectively addressed, (3) making clear the irrationality and imprudence of current environmental decisionmaking under uncertainty, and (4) pointing out the impossibility of achieving conservation goals by management that attempts to achieve economic optima. 相似文献
1000.
应用Harr-Gaussian小波变换对图形图像的边缘进行频域分析,建立边缘测量的物理模型, 并用带宽匹配方法和远心测量光学系统,在大景深物体测量中获得准确的结果.
关键词:
小波变换
边缘测量
测不准原理
远心系统
图像识别
自动检测 相似文献