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Entering Sample Information
Click on SAMPLE in the Main Instrument Panel. Select the sample (IWS) from LIMS tree or type in Text_ID. Click Continue. If you type in a Filter Code IWS, the software will only bring up the IWS sample, which can be handy if your IW has a lot of children.
Figure 11. Entering sample information.
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Figure 14. Acid dispenser reminder prior to starting the alkalinity measurement.
Once the pH measurement is complete, you will see a guide box again.
Measuring Alkalinity
1. | On the Alkalinity/Standard tab, ensure dispensing rate, drift span, and standard ratio are set correctly (Figure 7). |
2. | Ensure the water bath temperature is set to 25°C and pipette sample in titration vessel. |
3. | After rinsing the electrode with DI water and gently blotting dry with a Kimwipe, insert the electrode tip into sample (not touching the bottom of the cup or stir bar). |
4. | Click SAMPLE. |
5. | Select measurement type from the list, enter operator name (this must be the same as LIMS user ID), text_ID, and sample volume (Figure 8). Click OK. |
6. | After taking the initial mV and pH readings, the software prompts the user to insert the acid dispensing tip and click GO (Figure 9). If you make a mistake, click ABORT and no acid will be added to the sample. After clicking GO, the sample will be titrated to completion. |
7. | Click Done/Save to upload data (see LIMS Integration). |
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Figure 15. Measuring Alkalinity. The plot on the left side is the signal coming directly from the electrode in real time. The y-axis is the mV reading, and the x-axis is time in seconds. The readings will continue until the drift tolerance stability criteria is satisfied, which provides a final mV reading.
The green trend on the plot right side of the figure is the trend of mV readings vs. acid additions in ml. The mV readings come from the final value reached upon satisfying the stability criteria.
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1. | When the titration is complete, the Alkalinity Calculation screen opens. Unlock the Gran factor axis. |
2. | Zoom in on the Gran factor points. |
3. | Select the cursor and move to the point to be deleted. |
4. | Click Delete Data and then click Ok - Save when finished. |
Figure 17. Gran Factor Points (blue = Gran factor F, red = optimum mV range for linearity: 220–240 mV).
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