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直接电位法是目前离子选择性电极法中应用较多的一类方法,其中,根据被测溶液的具体情况,又有多种具体方法。对于较复杂的溶液体系,含同一种被测离子而具体每一试液组成差别较大时,多采用标准加入法、Gran作图法等。一次标准加入法误差较大,Gran作图法则须进行多点增量电位测定并作图,而且,这两种方法都须同时另测实际Nernst斜率,步骤繁复。二次标准加入法保持了多点增量法的基本优点,又避免了Gran作图法的麻烦,是较适用于日常测定的方法。
Direct potential method is currently used in ion selective electrode more a class of methods, which, depending on the specific circumstances of the solution under test, there are a variety of specific methods. For more complex solution system, containing the same kind of test ion and the specific composition of each test solution, the greater use of standard addition method, Gran mapping and so on. The error of a standard addition method is large. The Granogram method needs to measure and plot the incremental potentials. Moreover, both methods must measure the actual Nernst slope at the same time and the steps are complicated. The quadratic standard addition method retains the basic advantages of the multi-point incremental method and avoids the hassle of Gran mapping, making it a more suitable method for routine determination.