Roche Cedex Bio - Page 333

Roche Diagnostics
Operator’s Manual · Version 3.4 C-7
Cedex Bio analyzer 8 Data analysis methods
Photometric measurements
Monochromatic measurement
calculation
The blank measurement is calculated using the following formula:
The absorbance is normalized using the following formula:
Bichromatic measurement
calculation
Volume correction
Volume correction is carried out for every absorbance calculation.
All absorbencies are corrected using the volume ratio ( ).
This is necessary since, with each addition of liquid, the reaction mixture becomes
more diluted, while the path length of the light and the measuring window remain
constant. Volume correction is carried out for all points.
The following equation is used for volume correction:
Raw absorbance of point 1 of an empty cuvette at the requested
wavelength λ.
Blank raw absorbance at wavelength λ. (Corresponds to a water-filled
cuvette.)
Raw absorbance of each point (n) at the requested wavelength λ.
Absorbance of water at the requested wavelength. This value is
calculated from the difference of a cuvette filled with water and an
empty cuvette (air/water calibration system check).
Normalized absorbance of each point (n) at the requested
wavelength λ.
A
blank
λ() A
raw cuv
λ 1(,) A
H
λ()
O
2
+=
AN
cuv
λ n,()A
raw cuv
λ n,()A
blank
λ()–=
A
raw cuv
λ 1(,)
A
blank
λ()
A
raw cuv
λ n(, )
A
H
λ()
O
2
AN
cuv
λ n(,)
Raw absorbance value of all points of an empty cuvette at the
requested wavelength.
Absorbance value of a cuvette filled with water at the requested
wavelength.
Normalized absorbance values of a cuvette.
Main wavelength.
Reference wavelength.
AN
cuv
λ n,() A(
raw cuv
λ
1
n,()A
blank
λ
1
()) A
raw cuv
λ
2
n,()( A
blank
λ
2
()––()–=
A
raw cuv
λ n,()
A
blank
λ()
AN
cuv
λ n,()
λ
1
λ
2
Volume-corrected absorbance of each point (n).
Normalized absorbance of each point (n) at the wavelength λ.
Starting volume of point n of a cuvette before the last addition is
made.
Final volume of cuvette after the last addition.
initial volume final volume⁄
A λ n,()
AN
cuv
λ n,()V
cuv
n()⋅
VF
cuv
-----------------------------------------------------=
A λ n,()
AN
cuv
λ n,()
V
cuv
n()
VF
cuv