Metrohm 726 Titroprocessor - Manual (Page 144)

8.2 DET
726 Titroprocessor, Instructions for use 138 138
8.2.3 EP recognition
If there is a possibility of several equivalence points occurring in one titra-
tion, correct evaluation will depend on the criteria for recognizing the EPs
being correctly set.
ЪДДД EP Recognition ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД¿
³ ³
³ Equivalence points window min. EPC 5.0 ³
³ Gen. lower limit pH min upp. pH max ³
³ pK/HNP Evaluation off ³
³ ³
³ Windows Fixendpoints ³
³ EP# from ... to [pH] EPC [] F# M.value [pH] ³
³ ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД ДДДДДДДДДДДДДДДДД ³
³ 1 min max 5.0 1 off ³
³ 2 off off 5.0 2 off ³
³ 3 off off 5.0 3 off ³
³ 4 off off 5.0 4 off ³
³ 5 off off 5.0 5 off ³
³ 6 off off 5.0 6 off ³
³ 7 off off 5.0 7 off ³
³ 8 off off 5.0 8 off ³
³ 9 off off 5.0 9 off ³
АДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД QUIT ÄÙ
Equivalence points are evaluated according to the so-called equivalence
point criterion (ERC), which is calculated with a special algorithm using the
1st derivative (dMV/dV) of the titration curve. It is a measure of the severity
of the jump in equivalence and takes greater account of gentler jumps than
of steep jumps. The primary criterion for recognizing an equivalence point is
the value of the ERC, which must exceed a pre-set threshold value (EP crit.).
dMW/dV
[ERC]
V[mL]
20
min. EPC 5
70
EP1
EP2
U[mV]
gen. lower limit
gen. upper limit
gen. EP window
EP2
EP1
V[mL]
The second criterion for recognizing an equivalence point is the measured
value area in which it occurs, the so-called EP window.
One can define a general EP window in which EP recognition will proceed in
line with specific criteria (such as greatest, last or all EPs).
On the other hand, EP recognition can also take place in several EP win-
dows (measured value areas), to each of which a certain equivalence point
is allocated. The EP windows must not overlap.