Another important issue regarding the practical application of
any pH sensor is its memory effect of hysteresis [44]. The hysteresis
width was determined as the difference of measured pH sensor
potentials at the beginning and the end of a loop cycle defined as
pHx?pHy?pHx?pHz?pHx. Yet again, the best performance
was evidenced for electrode type B that exhibited hysteresis width
of only 2 mV (Table 1). This is comparable or better than the hysteresis
characteristics of earlier reported single pH sensors and
sensor arrays, as overviewed by Chou and Hsia [45].