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Calibrating the electrode
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Standard ratio correction
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Drift Span
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Cleaning up after Measurement
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Data Handling
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To select a saved standard ratio correction, double-click it.
Drift Span
A drift span of 30 (default) indicates that a minimum of 30 measurements will be taken after each addition of titrant (acid). The difference between the first and last measurements is compared to the drift tolerance specified in the rate program (see Creating a New Dispensing Rate Program). Generally, drift tolerance starts at 0.10 mV/s. Drift tolerance acts as follows:
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The mV readings come from the final value reached upon satisfying the stability criteria.
Cleaning up after Measurement
1. | Remove electrode from cup. |
2. | Rinse electrode with DI water in squeeze bottle. |
3. | Blot the electrode dry with a Kimwipe. Do not rub the electrode, which could cause static charge buildup. |
4. | Place the electrode in a storage container containing 3 M KCl. |
5. | Rinse and dry the acid dispensing tip and stir bar. |
6. | Pipette or pour the titrated alkalinity IW sample into a container to ship to repository or scientist. |
7. | Write on label how much HCl was added during titration. |
8. | Rinse the titration vessel cup with DI water and dry. |
Data Handling
Editing Gran Factor Points
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Data Reports
Data reports are not available at the instrument, but data can be viewed on the View Datalog tab (Figure 11). Also, the software appends the alkalinity results to the DAT file C:\ALKALINITY\LOG\ALKALINITYSAMPLES.DAT. The best way to view the alkalinity values to be used in graphs and reports is via LIMS Reports. It is also highly recommended to record the alkalinity and pH values in the blue laboratory notebook to protect against inadvertent data loss.
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Analysis | Component | Unit | Description |
ALKALINITY | alkalinity | mM | Ability of a solution to neutralize acid to the equivalence point of carbonate |
pH | NA | Acidity or basicity of a solution (–log[H+]) | |
acid_quantity | µL | Amount of 0.1 M HCl added to the sample during titration | |
correction_factor | — | Correction factor for non-ideal behavior of samples to adjust calibration | |
ALK_QAQC | alkalinity | mM | Ability of a solution to neutralize acid to the equivalence point of carbonate |
pH | NA | Acidity or basicity of a solution (–log[H+]) | |
acid_quantity | µL | Amount of 0.1 M HCl added to the sample during titration | |
correction_factor | — | Correction factor for non-ideal behavior of samples to adjust calibration | |
slope | — | Slope of the calibration equation | |
intercept | — | Intercept value of the calibration equation | |
corr | Rho | Correlation coefficient of the calibration |
Uploading Data to LIMS
When the alkalinity titration finishes, the GRAN-METHOD screen shows the slope information, correction factors, and final alkalinity value (Figure 14).
Edit outlier Gran factor points, if necessary (see Editing Gran Factor Points). If satisfied with the results, click Ok/Save to load the values into LIMS.
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Health, Safety, & Environment
Safety
Wear personal protective equipment including close-toed shoes, lab coat, gloves and safety glasses when working with acids of any strength.
Use a fume hood when making solutions from concentrated acids.
Pollution Prevention
Make reagent and standard solutions in quantities no larger than needed to complete sample analysis.
Waste Management
Neutralize acid solutions before disposal.
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Maintenance/Troubleshooting
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– | Make sure the probe storage container is filled with 3 M KCl solution and the reservoir is filled with 0.1 M HCl solution. |
– | Ensure no air bubbles are present in the acid dispensing line. Press DOS on the body of the titrator to push acid through the line and remove air bubbles. |
– | Change out the Drierite trap when ~50% of the color turns from blue to pink. |
| – | In case of a bubbling noise, top up your temperature-controlled water bath. Use tap water. Check titration vessel for air bubble and eliminate if present. |
Consumables
Electrode: Metrohm 6.0234.100 or equivalent. |
0.1 M HCl, Fisher CH5009 |
Microvalve buret tip, Metrohm 020683244, CM5129 |
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