Ocean Optics OOISensors - Manual (Page 132)

C: pH Sensor Theory of Operation and Calculations
Model # 4
In addition to previous, it uses both acid and base peaks
LowBuffer
pH LowH
− = 10
HighBuffer
pH HighH
− = 10
correct for baseline
aselineAbs LowBufferB A A
bs LowBufferA bs LowBufferA
− = − − ] [ ] [
s BaselineAb HighBuffer A A
Abs HighBuffer Abs HighBuffer
− = − − ] [ ] [
aselineAbs LowBufferB HA HA
bs LowBufferA bs LowBufferA
− = ] [ ] [
s BaselineAb HighBuffer HA HA
Abs HighBuffer Abs HighBuffer
− = ] [ ] [
(Continued)
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
] [ * ] [ *
] [ * ] [ * ] [ * ] [ *
] [
− −
− − − −
−
−
−
=
Abs HighBuffer bs LowBufferA
Abs HighBuffer bs LowBufferA Abs HighBuffer bs LowBufferA
HighpHAbs HA HighH HA LowH
HA HA HighH HA HA LowH
HA
] [ * ] [ *
] [ * ] [ * ] [ * ] [ *
] [
−
−
=
HighpHAbs
HighpHAbs
A
HA
t DyeCons
] [
] [
tan
−
−
=
if s BaselineAb HA HA
Abs HighpHAbs
− > ] [ ] [ then 5000 = Ratio else
HighpHAbs Abs
HA s BaselineAb HA
t DyeCons
Ratio
] [ ] [
tan
− −
=
If or
( )
0005 . 0 ≤ Ratio
( )
5000 ≥ Ratio then 0 = pH
else
) Ratio log( Ratio =
Ratio pK pH + =
122 FOXY-AL300-000-02-0207