14
Introduction,
continued
•
Thoroughly rinse and blot the electrode dry between
sample measurements. Remove the bulb guard before
measuring low ionic strength samples to prevent
transferring contaminants to the next sample, or rinse with
small volumes of sample.
•
Analyze samples shortly after collecting them. Weakly
buffered alkaline solutions can absorb carbon dioxide
causing downward drift of pH readings. Cover samples if
necessary. When measuring LIS samples requiring high
levels of accuracy, use the LIS accessory sample chamber.
•
A multi-point calibration will ensure more accurate
measurements than a single point calibration.
1.5 Checking the Slope
After calibrating the electrode with fresh buffer, check the slope
using the sens
ion
meter’s calibration review option. A slope of
-58 ±3 mV indicates a properly functioning electrode.
1.6 Accessories
1.6.1 Hach Low Ionic Strength Sample Chamber Kits
The Hach Low Ionic Strength Sample Chamber Kit
(Cat. No. 51899-00) prevents sample contamination by carbon
dioxide. When a sample absorbs carbon dioxide from the
atmosphere, carbonic acid forms and the pH of the sample
decreases.
The kit includes a sample chamber with a cap suitable for:
•
Measuring the pH of a grab sample while reducing the
sample’s exposure to the atmosphere.
•
Measuring the pH of a flow or plug-flow sample with no
exposure to the atmosphere.
