Hanna Instruments HI 4101 - Manual (Page 7)

7
VII VII VII VII VII. General Guidelines General Guidelines General Guidelines General Guidelines General Guidelines
•
Calibration standards and sample solutions should
have the same ionic strength. ISA should be added to
both samples and standards immediately before tak-
ing measurements.
•
Calibration standards and sample solutions should be
at the same temperature. Thermally insulate solution
vessel from magnetic stirrer with cork or other insulat-
ing medium.
•
Calibration standards and sample solutions should
be stirred at the same rate using identical sized stir
bars.
•
Surface coating or “wetting“ the PTFE membrane will
effect the response. Inspect sensor before using. Re-
place PTFE membrane if damage is evident.
•
Rinse electrode with distilled or deionized water be-
tween samples and dab dry with lab wipe or other soft
disposable absorbent toweling.
•
Check calibration every 1-2 hours.
•
Position sensors at an angle of approximately 20° to
lessen bubble adherence from solution out-gassing
due to temperature change.
•
Close container with plastic wrap or use
2 or 3 necked flask to prevent gas from leaving.
•
Gently pulling cable will permit an exchange of fill
solution at membrane surface. Re-Calibration is re-
quired.
ions are capable of reducing the ammonia concentration.
If other volumes of sample/standard are used, add ISA at 2
parts per 100 parts standard/sample.