Measurement of Physiological pH in Biological Specimens

描述(由申请人提供)：拟议研究的目标是(1)消除用于诸如血浆等生理样本的pH标准化的各种经验惯例的离子强度限制，并证明Pitzer离子相互作用理论方法的合理性，该方法使用标准缓冲液中所需的氯离子在离子强度i=0.16m时的单个离子活度系数来分配pH值，与在血清中发现的类似；(2)采用Pitzer公式将在建立自洽的pH标度方面发挥重要作用；以及(3)在有限离子强度(而不是I=0.0m)的“真实”条件下，用有液结和无液结的电化学池测量电动势的实验研究。长期目标是大大改善不确定度小于或等于0.002的主要参考标准的酸碱度测量状况。利用等渗盐水作为简单基质，选择了8个新的生物系统进行初步研究：(T)MOBS(0.04m)，NaMOBSate(0.04m)；(2)TAB(0.04m)，NaTABSate(0.04m)；(3)HEPBS(0.04m)，NaHEPBSate(0.04m)；(4)CABS(0.04m)，NaCABSate(0.04m)；以及类似的0.05m缓冲液成分。使这些数据在临床化学中得到广泛使用是基本的。该项目的具体目标涉及(I)测定MOBS、TAB、HEPBS和CAB在5-55摄氏度，包括37摄氏度(体温)下的热力学离解常数，因为文献中没有这些重要生物缓冲液的数据；(Ii)计算8种有用的标准参考溶液(每个缓冲液中两种)的pH值，其离子强度与生理液体中的在5-55xC温度下的离子强度相似。例如，溶液的组成为：(A)0.04M MOBS+0.04M NaMOBSate+0.12M NaCI；和(B)0.05M MOBS+0.05M NaMOBSate+0.1Tm NaCI；(Iii)通过使用高度可重复性的流动连接池，最大限度地减少液体连接电势的误差，以便确定可操作的pH值；(Iv)研究盐水介质中NaCI对调节体液中氢离子的基本离子过程的定量影响；以及(V)根据Pitzer约定，估计可靠的pH值所需的单离子活度系数。

DESCRIPTION (provided by applicant): The goal of the proposed research is (1) the removal of the ionic strength restriction of the various empirical conventions for pH standardization of physiological samples such as plasma, and the justification of the Pitzer ion interaction theory approach to assignment of pH values using the required single ion activity coefficients of the chloride ion in the standard buffers, at an ionic strength I = 0.16 m, similar to that found in serum; (2) adoption of the Pitzer formulation will play an important role for the establishment of a self consistent pH scale; and (3) experimental studies of dissociation equilibria under the "real" conditions at finite ionic strength (as opposed to I = 0.0 m) using electro-chemical cells with and without liquid junction for electromotive-force measurements. The long-term goal is to greatly improve the state of pH measurements for primary reference standards with uncertainties less than or equal too .002. Utilizing isotonic saline as a simple matrix, eight new biological systems are chosen for study in the initial stages: (t) MOBS (0.04 m), NaMOBSate (0.04 m); (2) TABS (0.04 m), NaTABSate (0.04 m), (3) HEPBS (0.04 m), NaHEPBSate (0.04 m); and (4) CABS (0.04 m), NaCABSate (0.04 m); and similarly with 0.05 m buffer compositions. It is fundamental to have these data available for wide use in clinical chemistry. The specific aim of the project involves (i) to determine the thermodynamic dissociation constants of MOBS, TABS, HEPBS, and CABS at 5 to 55 degreesC, including 37 degrees C (body temperature), since no data are available in the literature for these important biological buffers; (ii) to calculate pH values for eight useful standard reference solutions (two from each buffer) at ionic strengths similar to those in physiological fluids at temperatures from 5 to 55xC. For example, the solutions have the compositions: (a) 0.04 m MOBS + 0.04 m NaMOBSate + 0.12 m NaCI; and (b) 0.05 m MOBS + 0.05 m NaMOBSate + 0.1t m NaCI; (iii) to minimize the errors from liquid junction potentials by using a highly reproducible flowing junction cell, so that the operational pH values can be ascertained, (iv) to study the quantitative effect of NaCI in saline media on the essential ionic processes which regulate hydrogen ion in body fluids, and (v) to estimate the single ion activity coefficients, based on the Pitzer convention, required for reliable pH values.