horiba 5002S-10C, Instruction Manual

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60

Impact of coexistent substances
Because ammonia electrode determines ammonia concentration by
measuring pH change in inner solution caused by ammonia gas
permeating through the membrane, presence of acidic or basic gas other
than ammonia causes error. Such acidic gas as H
2
S or CO
2
, however, is
ionized in alkali region and does not exist as acidic gas, so that no problem
is created as long as the sample is measured in alkaline state.
On the other hand, the presence of volatile amine, gives error on indication
because it generates basic gas under alkaline state.
In any sample in which organic solvent such as acetone and alcohol is
included, the membrane is damaged or permeated by the organic solvent
so that indication becomes unstable to inhibit measurement.

Response time
The response times of ammonia electrodes differ depending on factors
such as ammonium ion concentration, temperature, and the stirring speed.
In general, the response time tends to be shorter when the ion
concentration is high and longer when the ion concentration is low.
Furthermore, the response time may become shorter when a high
concentration solution is measured after measuring a low concentration
solution, while the opposite case may cause the response time to become
longer.
The time required to reach a reading value that is 95% stabilized is within
one minute in the case of a standard solution with a concentration ranging
from 10 mg/L to 100 mg/L.