The measurement of pH in saline and hypersaline media at sub-zero temperatures: Characterization of Tris buffers
The measurement of pH in saline and hypersaline media at sub-zero temperatures: Characterization of Tris buffers
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在零度以下温度下测量盐水和高盐介质的 pH 值：Tris 缓冲液的表征
DOI：
10.1016/j.marchem.2016.06.002
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发表时间：
2016
期刊：
影响因子：
3
通讯作者：
Papadimitriou S
中科院分区：
文献类型：
--
作者：
Papadimitriou S
在盐度（S）35的合成海水和S = 45-100的合成海水衍生盐水中，在25 ° C和0 °C以及合成溶液的凝固点（S = 35时为−1.93 °C至S = 100时为−6 °C）下，用电化学Harned电池严格表征Tris-HCl缓冲系统（pHTris）的总质子标度上的pH。常用的等摩尔Tris缓冲液[RTris= mTris/mTris-H += 1.0，其中mTris= mTris-H += 0.04 mol kgH 2 O-1= 2-氨基-2-羟甲基-1，3-丙二醇（Tris）的共轭酸碱对的摩尔浓度]的电化学表征产生的pHTris值随着盐度的增加和温度的降低而增加。非等摩尔Tris缓冲液变体（RTris= 0.5，mTris= 0.02 mol kgH 2 O-1和mTris−H+= 0.04 mol kgH 2 O-1）的电化学表征产生的pH值始终比等摩尔Tris缓冲液的pH值低0.3个pH单位。这与从Tris-H+解离反应的化学计量平衡导出的值一致，该化学计量平衡由亨德森-哈塞尔巴尔赫方程描述，pHTris= pKTris + logRTris，其中pKTris = Tris-H+的化学计量平衡解离常数，相当于等摩尔pHTris。这种一致性允许在本文报道的实验条件下可靠地使用Tris-HCl缓冲系统的其他RTris变体。这项研究的结果将有助于在盐水和高盐系统在零度以下的温度，如海冰盐水pH值的测量。
The pH on the total proton scale of the Tris-HCl buffer system (pHTris) was characterized rigorously with the electrochemical Harned cell in salinity (S) 35 synthetic seawater and S = 45–100 synthetic seawater-derived brines at 25 and 0 °C, as well as at the freezing point of the synthetic solutions (−1.93 °C at S = 35 to −6 °C at S = 100). The electrochemical characterization of the common equimolal Tris buffer [RTris= mTris/mTris‐H+= 1.0, with mTris= mTris‐H+= 0.04 mol kgH2O‐1= molality of the conjugate acid-base pair of 2-amino-2-hydroxymethyl-1,3-propanediol (Tris)] yielded pHTrisvalues which increased with increasing salinity and decreasing temperature. The electrochemical characterization of a non-equimolal Tris buffer variant (RTris= 0.5, with mTris= 0.02 mol kgH2O‐1and mTris−H+= 0.04 mol kgH2O‐1) yielded pHTrisvalues that were consistently less alkaline by 0.3 pH unit than those of the equimolal Tris buffer. This is in agreement with the values derived from the stoichiometric equilibrium of the Tris-H+dissociation reaction, described by the Henderson – Hasselbalch equation, pHTris= pKTris⁎+ logRTris, with pKTris⁎= stoichiometric equilibrium dissociation constant of Tris-H+, equivalent to equimolal pHTris. This consistency allows reliable use of other RTrisvariants of the Tris-HCl buffer system within the experimental conditions reported here. The results of this study will facilitate the pH measurement in saline and hypersaline systems at below-zero temperatures, such as sea ice brines.