Spectrophotometric determination of the glass electrode sensitivity

Calibration of a glass electrode is usually performed by means of pH standard solutions prepared according to well-validated methods. Although such standards are available for water solutions and some usual solvents, some situations may appear when not suitable pH standards are available. Here we present a method for determining the sensitivity (slope) of the glass electrode by combined potentiometric and spectrophotometric measurements on a series of pH indicator solutions. The intercept of the calibration line is not available by this method, but the slope alone is useful for performing acid or base determinations by mean of the Gran titration methods.