WEF Discussion Forums
Laboratory Management and Technical Issues
Orion 4 Star Ammonia ISE issue
I am trying to calibrate a new Orion probe #9512 using a new Orion 4-Star meter. Every time I try the standards read almost opposite of what they should (1 ppm reads around 15 ppm, 10 ppm reads around 5 ppm, and 100 ppm reads around 0.8 ppm). I've remade the standards, used an older probe of the same model, etc. Any suggestions?
I haven't performed ammonia analysis by ISE in awhile, but I'll try to help
We don't use the Orion 4 star meter, as we have an older Orion model. But, if I recall correctly, we had the same sort of problem when we attempted to calibrate it for the first time. Are you following through the entire calibration procedure or are you stopping as soon as you get wacky readings? If you are stopping, try following through on the entire calibration procedure even though your readings are strange. If you obtain an acceptable slope, then analyse a check standard and see if it is reading correctly. You may be suprised to find that it is.
The ammonia gas sensing electrode has a negative slope so until you get a negative slope in the machine the results will look bad. After calibration the results should be good. Some old machines we had to tell it that the slope was approximately a certain value as it could only make small adjustments.
HELP I AM NEW LAB SUPERVISOR AND AM TRYING TO UP DATE METTERS. I HAVE LOOKED AT ORION,HATCH AND YSI METTERS WHICH BRAND IS BETTER IN A LAB SITUATION
Perhaps you have already addressed the situation with the NH3 probe by now. However, I would like to add that it is a good idea to run the probe function test if it is determnined that neither the standards nor the meter (at the extreme) are the cause of the irratic or erroneous readings.