Biomedical Engineering Reference
In-Depth Information
from the mobility data measured by capillary electrophoresis [25,26]. However, only
the
X
-reciprocal method that employs the equation
(
μ−μ
=−
)
A,eff
A
K
(
μ
−μ +
)
K
(
μ −μ
)
(2.22)
A
, ff
A
A
C
A
[]
provides the stability constant directly. In this method, the (
μ
A,eff
-
μ
A
)
[
C
] values
are plotted against (
μ
A
) and the stability constant,
K
A
, results as the-slope of
the obtained linear dependence. According to the recently proposed linearization
method that rearranges Equation 2.21 in the form
μ
A,eff
-
1
μ−μ
A
,eff
μ=
+μ
(2.23)
A,eff
AC
K
[]
C
A
the stability constant,
K
A
, and the mobility of the complex,
μ
AC
, are obtained simul-
[
C
],
K
A
results as the (slope)
−1
taneously [27]. If
μ
A,eff
is plotted against
μ
A
-
μ
A,eff
of the obtained linear relationship and
μ
AC
as the intercept. The linearization can be
easily done in Excel. If we substitute the demanding statistical procedure reported
in [27] for the easy Excel calculation, the effect on the calculated
K
A
and
μ
AC
values
is minimal [28]. This i nding is in accordance with a previously reported similar
observation [25].
Mathematically, it is possible to calculate logarithm, and, consequently, p
K
value,
only from dimensionless quantities. The standard method how to eliminate a quan-
tity dimension is to replace the quantity having the dimension, e.g., [
A
], [mol/L],
by a dimensionless relative quantity of the same magnitude, e.g.,
0
A
[
Ac
. This is
reached if the arbitrary reference quantity, e.g.,
0
c
, has the dimension of the quantity
to be normalized. Evidently, the reference quantity needs to be of the unit mag-
nitude, e.g.,
0
c
= 1 mol/L. Applying this approach, we obtain the normalized stoi-
chiometric stability constant,
0
A
K
, that is dimensionless and of the same magnitude
as
K
A
.
0
A
can be recalculated to the thermodynamic stability constant,
th
A
, if
K
K
each of the quantities participating in the dei nition of
0
K
is recalculated to the
standard conditions by means of a respective dimensionless coefi cient,
γ
A
.
Previously, these coefi cients were called activity coefi cients. Applying these steps,
we can write [17]
γ
, e.g.,
γ
cc
00
γ
th
0
AC
A
C
AC
KK
=
=
K
c
(2.24)
A
A
A
0
γγ
γγ
AC
AC
AC
2.4 CHIRAL SELECTORS
The compounds intended for a routine application as chiral selectors must meet
various demands in addition to those discussed above. It is a must that the chi-
ral discrimination capability of the compound working as a chiral selector is not
dependent on time at least for one working day. This feature is conditioned by both
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