离子选择电极二次标准加入法的计算方法及其应用

在离子选择电极分析法中,二次标准加入法得到较广泛的应用。若加入标液体积相同,已有人提出图算法及查表法等。文献〔6〕在严密论证的基础上,设计了简单快速的计算机解法,本文对加入标液体积不同时,如何用计算机求解等问题进行了研究。并把所得结果用于实际测定中。本文的理论部分只写出证明的梗概,因文献〔6〕的一些方法原则上可以处理本文所提的问题,必要时可参考文献〔6〕。     

离子选择电极多次标准加入法的摄动理论

多次标准加入法各测量点的Nernst方程为上式中,E~°=E~((°))+Slgγ_i。在以往的计算如三参数拟合法中,就把E~((°))当作常数来处理。这在E~((°))及γ_i变化很小的情况下是可行的。为此,必须规定严格的实验条件。如加入标液体积必须较小且浓度较大,添加次数不能太多,要加性能很好的离子强度稳定剂等等。否则三参数拟合法的计算结     

袖珍程序计算器在离子选择电极二次标准加入法中的应用

在离子选择电极分析法中,二次标准加入法的应用较广泛。带微处理机的离子计和微处理机在基层尚不能普及,为发挥现有仪器的作用,在前人工作的基础上,我们试用CASlOfx-3600pDS-5,BL-818等袖珍程序计算器与其配合,编制了计算程序,能较快地进行结果计算。其他带储存器的程序计算器也可参考使用。二次标准加入电位法中Nernst方程式为     

离子选择性电极标准加入法研究——Ⅲ、二次标准加入误差规律探讨

二次标准加入法(以下称方法)是离子选择电极分析较为简便、实用的实验技术,但一般精度不甚理想。因此,近年对其误差规律的研究受到关注,并导出一些误差函数式和曲线。然而均未能准确、定量地阐明方法的基本问题。文只是认为方法存在一误差“放大效应”。据笔者研究,方法的电极斜率S系一待测量,具有非常规的变量性质。上述文献作者均未认识这一特殊性质。文用烦琐的Monte Carlo模拟法分别导出误差曲线和式,这种数学处理过程含将S记为恒量的浓度-电势换算步骤。另外将三次电势测量误差用统一的标     

浓度同倍数递减离子选择电极标准加入法

本文报道了试液和标液浓度同倍数递减标准加入法。该法可测定几个体积均为V_x而浓度以C_x/N方式递减的试液(1≤N≤2),每个试液加等体积标液1次,在半对数算图上,各试液加入标液后的电位对原始试液电位差ΔE_N与浓度递减倍数N之间有线性关系,由交点N⁰解C_x=C_sV_s/[(N⁰-1)V_x+N⁰V_s]方程求得分析结果。该法不必测定电极的能斯特斜率。     

离子选择性电极多次标准加入法测量氟离子电极电势

建立了选择性电极中离子传递的模型。活化后的离子选择性电极 ,在电极表面形成活化层 ,阳离子和等量的阴离子分布在电极活化层的两侧 ,离子由溶液与活化层的界面经活化层传递到固定组成膜与活化层界面。在一定的条件下 ,电极膜电势随时间的变化与溶液和活化层的界面离子浓度随时间的变化成正比。在控制电势随时间的变化率基本恒定的情况下 ,方法被用于手工测量氟离子选择性电极电势 ,电极斜率。溶液离子浓度直接由 Gran方程求解。     

关于“离子选择电极标准加入法 研究Ⅲ.二次标准加入误差规律探讨”一文的商榷

编辑同志: 本刊在1986年2期81页上刊登了题示谭新民同志的文章,该文导出的误差公式实际上与所引文的误差公式完全一致的,且文中表1所列文公式算值是错误的,应与该文公式算值相同,其原因可能是作者未把文的△E_2(E_2-E_1)搞清楚。为更客观的说明问题,下面把谭文和文的误差公式作一比较。     

离子选择电极电位的标准加入法的直接计算机解

在电位分析中,Brand等作者采用了常规的多元非线性最小二乘法拟合其实验数据,获得了良好的结果,但是该法比较复杂。为此,本文根据Nernst方程可以方便地转化为仅含有一个未知量C_的特点,进而成功地对该问题直接进行一维优化计算。这个方法与前者具有同等的计算精度,但是它比前者简单,计算机程序也短三分之二。一、理论部分式(1)为Nernst方程,E为电极电位(E°是标准电位),V是溶液体积,C是溶液浓     

离子选择性电极标准加入法的测量误差研究

研究了离子选择性电极标准加入法的测量误差与标准溶液加入量的关系。从理论上导出了离子选择性电极一次标准加入法测量结果的相对误差计算公式。当加入标准溶液使试液增加的浓度等于试液原来的浓度，测量结果的相对误差最小。     

离子选择性电极多次标准加入法测定氟离子电极电势

建立了选择性电极中离子传递的模型,活化后的离子选择性电极,在电极表面形成活化层,阳离子和等量的阴离子分布在电极活化层的两侧,离子由溶液与活化的界面经活化层传递到固定组成膜与活化界面,在一定的条件下,电极膜电势随时间的变化与溶液和活化层的界面离子浓度随时间的变化成正比,在控制电势随时间的变化率基本恒定的情况下,方法被用于手工测量氟离子选择性电极电势,电极斜率,溶液离子浓度直接由Gran方程求解。     

Dopamine Ion-Selective Electrode for Potentiometry in Pharmaceutical Preparations

 This paper reports the construction and evaluation of a dopamine sensitive electrode and its usefulness for the determination of this compound by direct potentiometry in pharmaceutical preparations. The electrode comprised a carboxylated poly(vinyl chloride) membrane based on β-cyclodextrine dissolved in 2-fluoro-2-nitrodiphenyl ether and using tetrakis(p-chlorophenyl) borate as a fixed anionic site. For comparison purposes membranes with similar composition but including normal high molecular weight PVC were also prepared. The electrodes including carboxylated poly(vinyl chloride) presented linear response within the concentration range of 5×10⁻⁵ and 10⁻¹ mol dm⁻³ of dopamine with a slope of about 59 mV decade⁻¹ of activity, in the pH range of 2 to 7.5 units. The response time was less than 15 seconds. Selectivity coefficients for different interferents including sodium, potassium, ammonium, lithium, epinephrine and norepinephrine were evaluated using the separated solution method and no significant interferences were observed. The electrode displays useful analytical characteristics for the direct determination of dopamine in pharmaceutical preparations. Results with an average recovery of 98.6±0.3% were obtained. Received May 28, 1998. Revision March 2, 1999.     

不受电极斜率限制的离子电极标准加入法算图

格兰图在离子选择电极法中应用广泛,但该图要求电极响应的能斯特斜率为一定值。对电极斜率偏离理论值的情况进行修正已有报道。 本文提出一种不需任何电极斜率校正步骤的算图,即以加入标准溶液后电位的变化值△E与实际斜率S的比值△pe对加入标准溶液体积Vs作图的计算图(简称为△pe格兰图)。在实际操作中,根据测得的△E值和S值,经换算为△pe后,即可在标准算图上作图进行结果计算。克服了作空白溶液线或共线图线时可能引进的误差,简化了结果处理过程。此外,对不同价态离子的测定,该算图纵坐标标度△pe不变,不必扩大或缩小,作图十分方便。     

An Analysis of Operational Conditions for the Double Addition Method of Determining Ions From Electromotive Forces of Ion-Selective Electrode Cells

Abstract

The working conditions for the double addition method of potentiometric determination of unknown concentrations C_K of ions from the electromotive forces of appropriate ion-selective electrode cells have been analyzed in terms of operational equations, standard concentrations for additions, volume ratios of second to first additions, etc. The best operational conditions for minimizing errors on C_X are discussed.     

In Situ Measurement of Electrode Slope and Gravimetric Multiple Standard Addition Analysis by Ion Selective Potentiometry Without Prior Calibration of Electrode

Abstract

Two methods of calculation for the determination of an unknown concentration by gravimetric multiple standard addition analysis using ion selective potentiometry without prior calibration of the electrode have been described. These are based on simple calculation procedures involving linear least square fitting to Gran's equation to evaluate first the actual electrode slope ‘in situ’, then the unknown concentration and the cell constant. One method is iterative and the other is noniterative. The applicability of the methods has been demonstrated by processing the experimental data obtained by using fluoride and uranyl ion selective electrodes.     

"两次加标"-标准加入法在电极法测定中的应用

按GB/T5 75 0 - 1985中的氟化物标准加入法测定回收率时 ,由于水样中的氟化物含量是未知的 ,很难保证加入标准液的量既要使测定中加标前后两次电位值的变化在 30 4 0mV之间 ,又要使加标体积小于 0 .5ml。所以本法采用不预先加标 ,按常规测出E1、E2 两个电位值后 ,再多加一次标准液 ,读取第三个电位值E3,将E3相对于E2 进行计算 ,这时计算出的氟化物含量是水样中氟化物的含量与第一次加入标准液中所含氟化物量的总和 ,只要减去水样中氟化物的量就可以得到第一次加入标准溶液中氟化物的测定含量 ,并以此来评价测定回收率。在计算公式中将两…     

电位分析多次标准加入法的新算法

195 2年Ｇｒａｎ提出用图解法确定电位滴定终点 ,并成功地应用于电位滴定和电位分析多次标准加入法中 ,但该法必须事先知道电极斜率 ,或采用空白实验校正斜率。随后许多学者纷纷提出各种算法以弥补其不足 ,如Ｔａｙｌｏｒ级数法[1] 、单纯形调优法[2 ] 等等 ,但由于算法复杂而难以推广。我们发现如将两种较简单的数学方法即迭代法和一元线性回归法结合一体 ,可简便、快速、准确地计算出待测试液浓度 ,并同时得到电极斜率及截距。1　基本原理　　设待测试液浓度为ｃｘ,测得电位为Ｅｘ,由Ｎｅｒｎｓｔ方程知 :　　　　Ｅｘ=Ｅ +ｓｌｇｃｘ (…     

Determination of β-Lactam Antibiotics by Potentiometry with Ion-Selective Electrodes

Ion-selective electrodes for antibiotics from the penicillin series, with membranes based on three different classes of ionophores (anion exchangers, aza compounds, and metal phthalocyanines), were proposed. The electrochemical and performance characteristics of the sensors were studied and compared.     

Response Amplification of an Ion-Selective Electrode

Abstract

The response of an ion-selective electrode can be amplified by connecting the cell, which is composed of an ion-selective electrode and a reference electrode, in series. For a cell using 1, 2 or 3 valinomycin electrodes connected in series, the response slopes to 1 × 10^?5 ?1 × 10^?1 M K⁺ were 58, 116 and 174 mV/activity decade (a.d.) at 25°C, respectively. This amplification method would especially be useful for accurate determinations with electrodes in the range of low concentrations outside the Nernstian response or for determinations of polyvalent ions, in which both cases exhibit small emf response changes in changing the ion concentration.     

Preparation and Application Ion-Selective Electrode of Lomefloxacin

Lomefloxacin is an antibacterial agent of the 4-quinolone group with a broad spectrum of activity against Gram-positive and Gram-negative bacteria and has been widely used in clinical therapy⑴.Many methods have been used to determine Lomefloxacin, including UV-V1S, HPLC,fluorimetry. The aim of this paper is to report the preparation and the performance characteristics of lomefloxacin PVC coated carbon rod electrode.     

Some Characteristics of Ion-Selective Electrode Membrane Surfaces

Abstract

Some studies of the features of surfaces of PVC based liquid ion-exchanger and neutral carrier membranes, and of solid-state membranes of ion-selective electrodes are reviewed with respect to the application of X-ray fluorescence (XRF), Auger spectroscopy and scanning electron microscopy (SEM), Among the membranes discussed are those responding to (i) calcium for organophosphate type membranes, (ii) barium and polyalkoxylate non-ionic surfactants for PVC membranes based on complexes of barium with polyalkoxylate s, (iii) copper(II) for solid-state membranes of mixed copper(II) sulphide and silver sulphide, and (iv) sulphide and thiols for membranes of silver sulphide.