Instruction Manual
Ammonium Electrode
3
indicated by a slope of 90-100%. See the
TROUBLESHOOTING
section if the slope is not within this
range.
MEASUREMENT
Measuring Hints
The sensing membrane is normally subject to water uptake and might appear milky. This has no
effect on performance. All samples and standards should be at the same temperature for precise
measurement, preferably ambient temperature.
Constant, but not violent, stirring is necessary for accurate measurement. Magnetic stirrers can
generate sufficient heat to change the solution temperature. To counteract this effect, place a piece
of insulating material, such as styrofoam sheet or asbestos sheet, between the stirrer and beaker.
Always rinse the electrode tip(s) with distilled water and blot dry with a fresh tissue between
readings to prevent solution carryover.
Check the electrode for air bubbles adhering to the membrane surface after immersion in solution.
Agitate the electrode gently to remove the air bubbles.
A slow or sluggish electrode response may indicate surface contamination of the ammonium
electrode membrane. Soak the electrode tip in distilled water for about 5 minutes to clean the
membrane. Rinse the membrane and soak in diluted standard solution for about 5 minutes to restore
performance.
When measuring samples with high ionic strength, prepare standards with compositions similar to
that of the sample.
Dilute concentrated samples (over 0.1M) before measurement. Recalibrate every few hours for
routine measurement.
Sample Requirements
Make sure that the samples and standards are at the same temperature. About a 2% error will be
introduced for a 1oC difference in temperature. Temperature should normally be less than 40oC
with intermittent measurements allowed to 50oC.
All samples and standards must be aqueous. They must not contain organic solvents.
Interference found in Table 3 should be absent.
Units of Measurement
Ammonium concentrations are measured in units of parts per million as ammonium, parts per
million as N, moles per liter, or any other convenient concentration unit. Table 1 indicates some of
the concentration units.
