Ocean Optics OOISensors - Manual (Page 131)

C: ph Sensor Theory of Operation and Calculations
correct for baseline
aselineAbs LowBufferB A A
bs LowBufferA bs LowBufferA
− = − − ] [ ] [
s BaselineAb HighBuffer A A
Abs HighBuffer Abs HighBuffer
− = − − ] [ ] [
calculate theoretical maximum absorbance at peak
Abs HighBuffer bs LowBufferA
Abs HighBuffer bs LowBufferA Abs HighBuffer bs LowBufferA
HighpHAbs A HighH A LowH
A A HighH A A LowH
A
] [ * ] [ *
] [ * ] [ * ] [ * ] [ *
] [
− −
− − − −
−
−
−
=
calculate pK from the LowBuffer
HighpHAbs
bs LowBufferA
A
A
A
] [
] [
] [
−
−
− = , ] [ 1 ] [ − − = A HA
if 0
] [
] [
>
−
HA
A
then
] HA [
] A [
log pH pKlow
lowBuffer
−
− = else 0 = pKlow
calculate pK from the HighBuffer
HighpHAbs
Abs HighBuffer
A
A
A
] [
] [
] [
−
−
− = , ] [ 1 ] [ − − = A HA
if 0
] [
] [
>
−
HA
A
then
] HA [
] A [
log pH pKhigh
HighBuffer
−
− = else 0 = pKhigh
use the average
if and then 0 > pKhigh 0 > pKlow
2
pKlow pKhigh
pK
+
=
HighpHAbs
abs
A
s BaselineAb A
A
] [
] [
] [
−
−
−
−
= , ] [ 1 ] [ − − = A HA
If 0
] [
] [
≤
−
HA
A
then 0 = pH else
] HA [
] A [
log pK pH
−
+ =
FOXY-AL300-000-02-0207 121