Hanna Instruments HI 84442 - Manual (Page 5)

5
Potentiometric end point detection using a pH electrode is more objective than using visual end
point determinations with color changing indicators. The HI 84442 minititrator is a potentiometric
titrator. The instrument also can be used as a pH meter. The volume of titrant dispensed necessary
to reach the end point is then used to calculate the water alkalinity expressed in mg/L as CaCO
3
meq/L as CaCO
3
.
Interferences:
•
dissolved gases, lost or gained during samples storage or transport can modify the
alkalinity of the samples;
•
presence in the samples of the: precipitates, solid suspensions, oils, soaps can coat a pH
electrode;
To eliminate or diminish the interference effects, it is recommended:
•
to protect the samples against the atmospheric action (store in an airtight vessel);
•
to avoid vigorous shaking or mixing: stir gently;
•
maintenance of the pH electrode (see section Electrode Conditioning and Maintenance)