Metrohm 726 Titroprocessor - Manual (Page 146)

8.2 DET
726 Titroprocessor, Instructions for use 140 140
pK/HNP Evaluation
pK value and half neutralization potential
on | off
When the pK/HNP evaluation function is switched on,
the potential and the associated volume are filed in the
HNP1…9 resp. HNV1…9 system variables. These vari-
ables can be used for calculations.
Careful pH calibration is essential for pK and HNP
evaluations.
If initial dosing takes place, it must be smaller than ½
the dosed volume at the corresponding equivalence
point, otherwise the pK or HNP value cannot be evalu-
ated.
Note! pK values <3.5 or >10.5 must on principle be
regarded as unreliable, i.e. inaccurate.
Windows
Individual equivalence point windows
Individual EP windows can only be entered if 'window'
was indicated under ‘Equivalence points’.
EP# from … to[ ]
Limits of the individual EP windows
with DET_PH* pH -20…20 |min | max
with DET_U*, DET_IPOL* -2000…2000 mV |min | max
with DET_UPOL* -200 …200 µA |min | max
Different EP windows can be assigned for the various
equivalence points expected. This allows equivalence
points to be assigned with greater reliability to the given
calculation formulae, and suppresses undesirable EPs.
EP windows must not overlap. They must all lie within
the limits of the general EP window. The [Check
limits]
softkey is used to check the correctness of
the limits.
In any one EP window it is always the first equivalence
point found that is recognized. Other EPs are sup-
pressed. On the results page, the corresponding
equivalence point is marked with a '+' if there is more
than one EP in the corresponding EP window.
EPC [ ]
Equivalence point criterion for EP recognition
0…5…200
An individual EP criterion can be selected for each EP
window. It must, however, always be greater than the EP
criterion for the general EP window.