Ocean Optics OOISensors - Manual (Page 130)

C: pH Sensor Theory of Operation and Calculations
Model # 1
Looks at base peak only. No baseline correction. Uses nominal pK and slope.
HighpHAbs
Abs
A
A
A
] [
] [
] [
−
−
− =
] [ 1 ] [ − − = A HA
If
0
] [
] [
≤
−
HA
A
then 0 = pH
else
] HA [
] A [
log pK pH
−
+ =
Model # 2
Looks at base peak only. Corrects for baseline.
lineAbs HighpHBase A
s BaselineAb A
A
HighpHAbs
Abs
−
−
=
−
−
−
] [
] [
] [
] [ 1 ] [ − − = A HA
If
0
] [
] [
≤
−
HA
A
then 0 = pH
else
] HA [
] A [
log pK pH
−
+ =
Model # 3
Looks at base peak only. Uses the values of two buffers to predict absorbance of [A] High pH and [HA]
High pH.
LowBuffer
pH LowH
− = 10
HighBuffer
pH HighH
− = 10
120 FOXY-AL300-000-02-0207