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氟离子选择电极法在测试中应注意的问题 总被引:10,自引:0,他引:10
氟元素的测定方法主要有茜素酮比色法和氟离子选择电极法。前者使用试剂较多,但结果准确;后者具有结构简单牢固、灵敏度高、晌应速度快等优点而被广泛地应用。本文就氟离子选择电极法测试中应注意的问题进行归纳和总结。1 电极的响应极限氟离子选择电极在初次使用时,应首先测试其响应极限,由此可准确估计样品的最低检出限。氟离子选择电极的响应极限为0.05mg/L左右。若待测液中氟离子活度小于电极的响应极限,可使用标准加入法,克服因测试电位值与氟离子活度的对数不成线性关系造成的误差,满足分析测试的精密度和准确度。2 氟离子选择电极… 相似文献
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对离子选择电极法与新氟试剂光度法的特性指标进行了比对研究。结果表明,离子选择电极法检出限为0.01 mg/L,线性范围为0.04~1 900 mg/L,相对标准偏差为0.16%~0.30%,加标回收率为101%;新氟试剂光度法检出限为0.05 mg/L,线性范围为0.06~1.5 mg/L,相对标准偏差为1.05%~2.10%,加标回收率为105%。两种方法结果无显著性差异,但离子选择电极法与新氟试剂光度法相比,测定下限低,测定范围宽,精密度、准确度较高,因此选定离子选择电极法作为制定大气中氟化氢测定法国家标准的基础。 相似文献
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N.T.Crosby等曾详细地比较了饮用水和其它水质中氟化物的各种比色法和离子选择电极法,指出电极法的有效性。本文以自制流通氟电极为检测器,用于流动注射分析,测定了80样次/时的样品,减少了试剂和样品消耗,用峰高(峰顶电位和基线电位差)表示分析结果,消除了基线电位随时间漂移影响。同时,在其分析体系中,恒定的流速、高度重复的 相似文献
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HEPT类化合物的QSAR研究 总被引:3,自引:0,他引:3
为定量结构/活性相关性研究提取了量子化学参数,拓扑指数Am,分子连接性指数^mxt及疏水性常数,同时应用正交变换和最佳变量子集算法(Leaps-and-Bonds)进行了变量压缩和选择,进而实施了多元回归分析,并由此结果进行了HEPT类化合物(1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-thymine derivatives)的结构/活性关系的理论解释,进行了人工神经网络法对于该类化合物的活性预测,其结构明显好于多元回归法。 相似文献
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V. P. Lezina N. A. Andronova L. D. Smirnov K. M. Dyumaev 《Chemistry of Heterocyclic Compounds》1971,7(11):1438-1440
The dependence of the chemical shifts of the ring protons on the pH of the medium for a number of 4-hydroxyquinoline derivatives was studied by means of PMR spectroscopy. The dipolar and uncharged hydroxy forms exist in equilibrium in aqueous solutions. The effect of intramolecular hydrogen bonding on the character of the dependence of the chemical shift on the pH of the medium in the case of 3-piperidinomethyl-4-hydroxyisoquinoline was investigated. The possibility of the separate protonation of the ring nitrogen and the side-chain nitrogen in 3-piperidinomethyl-4-hydroxyisoquinoline was established. The distribution of the -electron density in 4-hydroxyisoquinoline is in good agreement with its chemical behavior.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1546–1549, November, 1971 相似文献
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V. P. Lezina N. A. Andronova L. D. Smirnov K. M. Dyumaev 《Chemistry of Heterocyclic Compounds》1971,7(11):1433-1437
The dependence of the chemical shift of the ring protons on the pH of the medium for a number of 3-hydroxyquinoline derivatives was studied by PMR spectroscopy. The regions of ionization of the molecules, which correspond to the ranges of acidic, neutral, and alkaline media, were found. In D2O, 3-hydroxyquinoline is present only in the uncharged hydroxy form. The presence of intramolecular hydrogen bonding in 4-dimethylaminomethyl-3-hydroxyquinoline has a substantial effect on the character of the dependence of the chemical shift on the pH of the medium; the existence of separate protonation of the nitrogen atoms of the ring and the side chain of 4-dimethylaminomethyl-3-hydroxyquinoline was established. The distribution of the -electron density in the 3-hydroxyquinoline molecule is in good agreement with its chemical behavior during electrophilic substitution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1540–1545, November, 1971. 相似文献
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通过在LS55型荧光-磷光-发光分光光度计上加装液滴产生及调节附件,采用计算机采集与分析处理数据,成功地研制了双通道液滴光化学传感装置.利用葡聚糖凝胶对复合维生素B中不同组分的选择性吸附来达到分离与同时检测的目的,并将其用于复合维生素B药片的分析,取得了满意的结果. 相似文献
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Tangney P 《The Journal of chemical physics》2006,124(4):044111
The theory underlying the Car-Parrinello extended-Lagrangian approach to ab initio molecular dynamics (CPMD) is reviewed and reexamined using "heavy" ice as a test system. It is emphasized that the adiabatic decoupling in CPMD is not a decoupling of electronic orbitals from the ions but only a decoupling of a subset of the orbital vibrational modes from the rest of the necessarily coupled system of orbitals and ions. Recent work [J. Chem. Phys. 116, 14 (2002)] has pointed out that, due to the orbital-ion coupling that remains once adiabatic decoupling has been achieved, a large value of the fictitious mass mu can lead to systematic errors in the computed forces in CPMD. These errors are further investigated in the present work with a focus on those parts of these errors that are not corrected simply by rescaling the masses of the ions. It is suggested that any comparison of the efficiencies of Born-Oppenheimer molecular dynamics (BOMD) and CPMD should be performed at a similar level of accuracy. If accuracy is judged according to the average magnitude of the systematic errors in the computed forces, the efficiency of BOMD compares more favorably to that of CPMD than previous comparisons have suggested. 相似文献
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