4. CALCULATION OF CATALYTIC ACTIVITY CONCENTRATION
For routine determination of the catalytic activity concent–
ration of CK in serum corrections for reagent blank and samp–
le residual aäenylate kinase blank rates may be omitted.
4.1 Molar Absorption Coefficient of the Monitored Product
The
m~lar ab~~rption
coefficien2s of
N~2PH
are:
628 m x_pol
at 334 nm, 630 m x mol
at 340 nm,
and 350
m x mol
at 365 nm.
4.2 Calculation at eonstant Pathlength
Using measurement at 340
nm
as an example, the catalytic con–
centration of CK is calculated as follows:
Symbol
b
i
E
Type of Quantity
Catalytic activity concentration
the increase in 340 nm absorbance
per seeond
Units
pkat/L
-l
s
l
v
Molar 340 nm absorption coeffi–
cient of
NADPH
=
630
Light pathlength 0.01
m2 x mol-l
m
Sample volume fraction: 0.04348
vol(L)/vol(Lj
l
4.2.1 Calculations for a Pathlength of 0.01 m
i
i
-l
s
b
=
=
x
630 x 0.01 x 0.04348
m 2 x mol-l x m
.E:
x
l
x v
i
b
=
=
i
x 3.651
x
0.27392
3
b
=
i x 3.651 x kat/m
b
=
i x 3651 jlkat/L
Calculated for a Measuring Time of 60 s:
b= i x 3651 x
~mol
x (60s)-l x L-l
b =
i
x 3651 U/L
b
=
i x 60.85 Fkat/L
mol
To convert
from~kat/L
to U/L multiply by 60.
To convert from U/ L to ykat / L divide by 60.
Klinisk kemi i Norden 2: supp/, 1990
*4 -905050
-l
x s
3 m
29
