4. CALCULATION OF CATALYTIC ACTIVITY CONCENTRATION
For routine determination of the catalytic activity concent–
ration of ASAT in serum corrections for reagent and sample
blank rates may be omitted.
4.1 Molar Absorption Coefficient of the Monitored Product
The
m~lar ab~~rption
coefficienzs of
N~2H
are:
618 m x 2ol
a! 1 334 nrn, 630 m x mol
at 340 nrn,
and 340 m x mol
at 365 nrn.
4.2 Calculation at eonstant Pathlength
Using measurement at 340
nm
as an example, the catalytic ac–
tivity concentration is calculated as follows
Symbol
Type of quantity
b
Catalytic activity concentration
d
Decrease of (decadic) 340 nm absorbance
per seeond
E
Molar 340 nrn absorption coefficient of
NADH
=
630
l
Light pathlength (0.01)
v
Sample volume fraction: 0.0833
vol(L)/vol(L)
4.2.1 Calculation for a Pathlength of 0.01 m
d
d
b=
x
ex l x v
630 x ·O.Ol x 0.08333
d
b=
=
d x 1.905
x
0.525
b=
d x
l.
905 x kat/m 3
b=
d x 1905 x pkat/L
Calculated for a Measuring Time of 60 s:
b
d x 1905 x J.lmol
(60s)-l
-l
=
x
x
L
b
=
d x 1905 U/L
b
=
d x 31.75 Jlkat/L
To convert
from~kat / L
to U/ L multip1y by 60.
To convert from U/L to ykat / L divide by 60.
Uni
t
y k at / L
-l
s
m2 x mol-l
m
l
-l s
2
-l
m x mol
mol
-l
x s
3 m
x m
4.2.2 Calculation for Other Pathlengths and for Other Volume
Fractions
Insert the pathlength ( unit: meter) and the volume fraction
(unit L) in the equation
ins~ead
of the figures given above.
Klinisk kemi
i
Norden 2: supp/, 1990
51
