Glass electrodes are commonly used to measure the pH of natural waters over various, sometimes wide, ranges of salinity (S). For such applications, the electrodes must be calibrated against solutions of known pH and salinity identical to those of the sample solutions. Well-characterized buffer solutions may be used for these calibrations, but if a wide range of salinity is to be encountered in the samples (e.g., as in estuarine transects), this approach is quite laborious. Previous work has demonstrated that for 28.5 < S < 36.1, pH electrodes can be efficiently calibrated spectrophotometrically in seawater because electrode intercept potential E₀ (a key calibration parameter) varies linearly with salinity over that range. The present work (a) characterizes pH electrode calibration parameters in seawater over a wider range of salinity (0.5 < S < 36) and (b) provides a simple and efficient method for creating and maintaining “river-to-sea” electrode calibrations over periods of months. Electrode calibration slope (g') was found to be insensitive to salinity, as expected. The value of this parameter, measured at S > 5, was reliably consistent with theoretical expectations, such that repeat verification needs to be conducted only occasionally. Electrode intercept potential (E₀), in contrast, was found to depend substantially on salinity: approximately linearly for 5 ≤ S ≤ 36 and substantially nonlinearly for 0.5 ≤ S < 5. Ignoring this dependence of E₀ on S can lead to pH misestimates as large as 0.24, with the problem being most severe at lower salinities. Based on these observations, a method was developed by which the dependence of E₀ on S can be rapidly ascertained by simultaneously measuring pH (spectrophotometrically) and electromotive force (potentiometrically) in seawater that is serially diluted to produce the full range of salinities to be encountered in sampling. Because no acid titrations are required, a full river-to-sea calibration can be acquired in <3 h. With occasional (daily to weekly) one-point checks/corrections for electrode drift, this calibration is stable for weeks to months.

玻璃电极通常用于在各种盐度（S）范围内（有时甚至很宽）测量天然水的pH值。对于此类应用，必须针对已知pH和盐度与样品溶液相同的溶液对电极进行校准。表征良好的缓冲溶液可用于这些校准，但是如果要在样品中遇到多种盐度（例如，在河口样带中），则此方法非常费力。先前的工作表明，对于28.5 <  S  <36.1，pH电极可以在海水中用分光光度法进行有效校准，因为电极截获电位E ₀（关键校准参数）在该范围内随盐度线性变化。目前的工作（a）表征了盐度范围较大（0.5 < S  <36）时海水中的pH电极校准参数， 并且（b）提供了一种简单有效的方法来创建和维持“河流到海洋”电极校准几个月的时间。如预期的，发现电极校准斜率（g '）对盐度不敏感。该参数的值（在S  > 5时测得）与理论预期值可靠地一致，因此仅需要偶尔进行重复验证。电极拦截电位（E ₀），与此相反，发现在盐度基本上取决于：大致线性5≤ 小号 ≤36和基本上非线性0.5≤ 小号 <5.忽略的这种依赖性ë ₀上小号可导致至pH misestimates一样大0.24，与在较低的盐度下问题最严重。基于这些观察，开发了一种方法，通过该方法，E ₀对S的依赖性通过同时测量海水中的pH（分光光度法）和电动势（电位法）（通过连续稀释以产生在采样中遇到的所有盐度），可以快速确定pH值。由于不需要酸滴定，因此可以在不到3小时的时间内完成完整的河海标定。偶尔（每天至每周）对电极漂移进行单点检查/校正，此校准可在数周至数月内保持稳定。