Ocean Optics Transmissive pH Probe - Manual (Page 9)

pH Probe Instructions
PH-BCG-TRANS-01-0210 9
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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


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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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
Sample pH
Sample
Abs Abs
Abs
11
log
…for each of the buffers. The y-axis shows the pH value of the buffers. This generates a plot such as
the one shown below: