Transient responses of glass electrodes in dilute solutions and freshwaters

The responses of a glass electrode to injection of different solutions into a flow injection analyser was examined. Solutions examined were acid stream water, nearly neutral natural and artificial lake water, distilled water, phosphate buffer and hydrochloric acid. Solutions of natural and artificial nearly neutral lake water responded more slowly than the rest. Buffer capacity and ionic strength influenced the response but were not the critical factors. The poor response was associated with the glass electrode and particularly with low cation concentrations. The effect increased in the order potassium and calcium, sodium and magnesium, ammonia. The appropriateness of glass electrodes in flow injection analysis of dilute neutral solutions was questioned.