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排序方式: 共有382条查询结果,搜索用时 31 毫秒
101.
同位素内标-多反应监测同步在线质谱全扫描确证火锅料中罂粟壳成分 总被引:1,自引:0,他引:1
建立了高效液相色谱-三重四极杆线性离子阱质谱测定火锅料中吗啡、可待因、蒂巴因、罂粟碱、那可丁等5种生物碱残留的确证方法。样品采用稀盐酸加热提取,正己烷除脂,阳离子混合机理固相萃取柱净化,5%氨化乙酸乙酯-甲醇洗脱,PAK ST色谱柱分离,5 mmol/L乙酸铵甲醇溶液-10 mmol/L乙酸铵水溶液(pH 3.6)作为流动相洗脱,电喷雾正离子模式下多反应监测同步增强子离子在线全扫描(EPI)。在该实验条件下,5种生物碱的LOD在0.05~0.5 μg/kg之间,增强型子离子全扫描水平限和LOQ在0.2~2 μg/kg之间,方法回收率为64.2%~110.6%, RSD为4.2%~12.5%。阳性样品的定性确证需采用其子离子全扫描质谱图与标准图库中子离子质谱图检索匹配。经测定多种火锅料,表明本方法操作简单、测定结果准确,可用于火锅料中5种生物碱残留的阳性结果确证分析。 相似文献
102.
Electrocatalytic Oxidation of Calcium Folinate on Carboxyl Graphene Modified CuxO/Cu Electrode
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Carboxyl graphene modified CuxO/Cu electrode was fabricated. The bare copper electrode was firstly anodic polarized in 1.0 mol/L NaOH solution in order to get CuxO nanoparticles, then the carboxyl graphene (CG) was electrodeposited on the CuxO/Cu electrode by cyclic potential sweeping. The electrocatalytic oxidation behaviors of calcium folinate (CF) at the graphene modified CuxO/Cu electrode were investigated by cyclic voltammetry. A positive scan polarization reverse catalytic voltammetry was used to obtain the pure catalytic oxidation current. The graphene modified CuxO/Cu electrode was served as the electrochemical sensor of CF, a highly sensitivity of 22.0 μA·(μmol/μL)-1cm-2 was achieved, and the current response was linear with increasing CF concentration in the range of 2.0×10-7 mol/L to 2.0×10-5 mol/L, which crossed three orders of magnitude, and the detection limit was found 7.6×10-8 mol/L (S/N=3). In addition, the proposed sensor was successfully applied in determination of CF in drug sample. 相似文献
103.
《Electroanalysis》2006,18(10):941-946
The application of linear scan voltammetry for sensitive determination of nitrite by using a disposable screen‐printed edge band carbon ultramicroelectrode (designated as SPUME) was reported in this study. The measurement with the SPUME can be performed in solutions of low ionic strength, e.g., natural waters, because the ohmic loses are negligible. The limiting oxidation current of nitrite showed a wide linear range up to 3 mM at the SPUME. A relative standard deviation of 2.46% (n=5) for analyzing 5 μM nitrite indicated a detection limit (S/N=3) of 0.38 μM. Real sample analysis of mineral and ground water samples as well as bratwurst food product showed satisfactory results. Since the SPUME is low cost and easy for mass production, the disposable nature further offers to application in diverse field of electroanalytical chemistry. 相似文献
104.
Takashi Sasaki Nobutaka Yamauchi Satoshi Irie Kensuke Sakurai 《Journal of Polymer Science.Polymer Physics》2005,43(2):115-124
Glass transition, cold crystallization, and melting of freeze‐dried poly(L‐lactide) (PLLA) prepared from dilute 1,4‐dioxane solutions were investigated by differential scanning calorimetry (DSC). Conventional DSC measurements of heating scans revealed that freeze‐dried PLLA prepared from a 0.07 wt % solution undergoes a two‐step cold crystallization (or reorganization) with a lower exotherm appearing at about 78 °C and with a higher broad exotherm between 110–155 °C. The peak temperature of the former exotherm is about 50 K lower than that observed for a reference bulk sample. Step‐scan mode DSC, which provides information essentially equivalent to that obtained from the temperature‐modulated DSC, revealed that the glass‐transition temperature is about 6 K lower than that of the reference bulk. These findings suggest enhanced chain mobility for freeze‐dried PLLA. Freeze‐dried PLLA that crystallized at 80 °C for 40 min was revealed to contain a rather large amount of rigid amorphous material (42%). © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 115–124, 2005 相似文献
105.
106.
Stathis Chadjiconstantinidis Markos V. Koutras 《Annals of the Institute of Statistical Mathematics》2001,53(3):576-598
Abstract. In this article we consider infinite sequences of Bernoulli trials and study the exact and asymptotic distribution of the number of failures and the number of successes observed before the r-th appearance of a pair of successes separated by a pre-specified number of failures. Several formulae are provided for the probability mass function, probability generating function and moments of the distribution along with some asymptotic results and a Poisson limit theorem. A number of interesting applications in various areas of applied science are also discussed. 相似文献
107.
108.
在工业辐照电子直线加速器中,电流发生器是电子束扫描设备中的重要部分,可控式电流反馈-电流镜产生扫描电流是一种新方法,其电流波形可被扫描均匀度指标修正,不仅可以得到良好的电子束扫描均匀度,而且还可以提高均匀扫描的速度。 相似文献
109.
110.
宣德官窑青花瓷的面扫描分析 总被引:4,自引:1,他引:3
用SRXRF对宣德时期官窑青花瓷片上的瓷彩进行面扫描分析,结果表明各元素分析线的峰面积有着不同的分布模式。根据与颜色浓淡、瓷彩上黄斑的耦合关系可以将K,Cr,Mn,Fe,Co,Ni,Cu,Zn,Hg,Rb,Sr,Y和Zr等13个元素分为3组。它可作为各个朝代青花瓷“指纹元素”的选择依据,并提出了研究瓷彩中黄斑的形成机制的新思路。 相似文献