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1. Select Calibrate Electrodes from the main Alkalinity interface.
2. Enter your range of buffers (4, 7, 10).
3. Select your Drift Span. The default drift span is 30.
4. Place 3 mL of the first buffer solution in the vessel. Add stir bar and immerse electrode in vessel. Remove the electrode from the storage solution, rinse with DI water, and blot dry with a Kimwipe. Do not rub the electrode, as this can cause a static charge. Insert the electrode tip into the titration vessel (not touching the bottom of the cup or stir bar). Confirm that the frit is in the solution.
5. Select Cal 1 and then Start.
6. When finished, clean vessel and the electrode.
7. Repeat steps 4–6 with each calibration buffer, selecting Cal2 and Cal3 when appropriate.
8. When all three buffers have been run, select OK-Save to save the calibration.
   

   Dispensing rate

   The rate at which the titrator dispenses the acid into the sample can be adjusted according to the expected alkalinity value. Higher alkalinities may require faster dispensing rates. The dispensing rate can be selected from a list of predetermined programs, or a new dispensing rate program can be created.

   Select Edit Rates from the main alkalinity interface.

   
   

   
   
   

   Standard ratio

   Calculating the standard ratio (estimated vs. actual alkalinity, “fudge factor”) for the anticipated range of alkalinity values accounts for measurement error in acid strength. Standard ratio can be calculated using borax solution, sodium bicarbonate solution, or IAPSO standard seawater, as necessary, to most closely match alkalinity values (within 5 mM, to preserve the first-order transfer function) of the unknown samples. Generally, IAPSO standard seawater is used to establish this ratio, and additional calibration standards are used if samples deviate >5 mM from the alkalinity of IAPSO (~2.325 mM). The measurement is repeated until at least 3 consistent measurements are obtained within 5% of actual value for each standard:

   -         IAPSO = 2.21–2.44 mM

   -         20 mM standard = 19–21 mM

   -         40 mM standard = 38–42 mM

   To start creating a standard ratio, select STANDARDS from the main alkalinity interface.

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Select the sample (IWS) from the LIMS database. Use the tree or type in the Text_ID in the appropriate field.

1. Place 3 mL of standard the sample in the vessel. Add stir bar and immerse electrode in vessel. Remove the electrode from the storage solution, rinse with DI water, and blot dry with a Kimwipe. Do not rub the electrode, as this can cause a static charge. Insert the electrode tip into the titration vessel (not touching the bottom of the cup or stir bar). Confirm that the frit is in the solution.
   
   

Select Continue.
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Click START. The software will guide you through.

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1. The first measurement that the system measuresmakes, is sample pH. Record the value in the blue book.
2. Insert the acid dispensing probe when prompted.

3. When the titration is complete, a window appears to let you know that the analysis is complete. Click Ok.

   
   

   

A Gran-Method window appears with the results of the titration. Write the Alkalinity Cor value in the blue book. This is the result with the standard ratio applied to it. Click Ok/Save. This will upload the result to LIMS assuming the MUT uploader is active.

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When finished, clean vessel and the electrode.

Click Ok/Save to save the results to the LIMS database. The value saved to LIMS and the value you need to note in the blue book is the “Alkalinity Cor” value. This is the value with the standard ratio applied to it.