Ocean Optics pH Sensor Patches, Probes and Cuvettes - Manual (Page 31)

PHSENSOR-TRANS-REFLECT-201111 25
Appendix A
Algorithms Used
pH Calculation
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
 
Sample pH
Sample
Abs Abs
Abs
Slope pK pH
11
log *
…where Abs
Sample
is the sample absorbance at 620nm with baseline correction, and Abs
pH11
is
the absorbance at pH 11 at 620nm with baseline correction.
Temperature Compensation
When you select Use Factory Calibration in SpectraSuite, the value for pK is adjusted via the
van’t Hoff equation based on the current temperature you entered:
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
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

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 
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






 






 






 
1 2
1 2
1 1
* 480
1 2
1 1
* 480
1 2
log
log
T T
T T
e pH pH
e pK pK
Resetting pK and Slope
An x-y plot is made using data obtained from intermediate buffers 5 through 8. The x-axis is of
the term:
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
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


Sample pH
Sample
Abs Abs
Abs
11
log