The
tip of the electrode in contact with the sample was 1 cm in length
(Fig. 1). Saturated calomel with double junction (R-683; Analion,
Ribeirão Preto, Brazil) was used as the reference electrode. The
two electrodes were connected to the potentiometer/pH meter
HI-9321 (Hanna Instruments, Woonsocket, RI, USA). Both elec