pH probe cleaning/recalibration time?

VaderWS6 · 07/29/2008, 11:47 AM

The last time I calibrated my Pinpoint pH probe was about a year ago. Should I clean in vinegar/recalibrate it once a year?

sps1-2-b · 07/29/2008, 12:40 PM

I've read that you're suppose to, but I haven't recalibrated mine for a year either. I'm tagging along to see if it's absolutely necessary. Thanks.

mille239 · 07/29/2008, 01:29 PM

I do mine every year, but the Mfg. recommends every 6 months. I think that is a little much, but if you track your readings, you'll know when it starts to slide in one direction ort the other.

(I'd replace your probes every 2.5 to 3 years as well)

The Saltman · 07/29/2008, 02:26 PM

The standard I heard on ph probes is after 1 year to replace. Lab grade ph probes could probably go 1.5 to 2 years.

MattAndKim · 07/29/2008, 03:34 PM

Will the pH meters you are using display probe nernst slope?
If they won't you can't really have any idea of the drift the probe has experienced. If they do, compare the slope to the allowable specification given by the probe manufacturer.

Probes with bad slopes can sometimes be cleaned with enzymatic cleaners, isopropyl alcohol, and other solvents without damage. Probes with low slopes can sometimes be regenerated with dilute acid solutions. Probes with high slopes are pretty much KIA, i've never heard of a fix for polarization (this results from leaving the probe energized in air).

If your slope checks out, but your pH has drifted considerably AND the asymmetry potential is significantly different from when the probe was new, your readings are suspect in my experience. Attempt to regenerate with acid if changing reference fill solution does not fix the problem.
The durability of lab grade pH probes depends on the make, the environment, and the fickle nature of pH probes. I personally would not expect a lab-grade pH probe to last this long in a biologic environment but YMMV.
This is all based on combination probes, i don't know about split probes.

If anyone has questions about care and feeding of pH probes, I have a bit of experience with combo probes in pure and treated water applications.

My practice for any important measurement is to immediately calibrate the probe prior to the measurement with buffers brought to the same temperature as the sample. I think for routine monitoring a weekly calibration is sufficient to maintain high accuracy. I would not trust a measurement taken in water flow as fluctuations in flow velocity and temperature will affect the reading.

07/29/2008, 11:47 AM	#1
VaderWS6 Registered Member Join Date: Nov 2003 Location: Kentucky Posts: 1,644	pH probe cleaning/recalibration time? The last time I calibrated my Pinpoint pH probe was about a year ago. Should I clean in vinegar/recalibrate it once a year? __________________ 2001 black T/A WS6~M6 ASC#6979 331rwhp/348rwtq Mods: !CAGS, Pro 5.0, TSP lid, BGRA, Raptor shift light, Strange 4.10 gears, Strano springs, SLP Bilstein shocks, GMMG exhaust Current Tank Info: Main reef:75 gallon w/ 2 250watt Radium 20k run on a PFO dual 250watt HQI ballast w/Lumenbright mini reflectors. 4 110watt VHO actinics for dawn/dusk,Geo kalkreactor,Litermeter 3,Xtreme 160 skimmer,2 Vortech mp40w's

07/29/2008, 01:29 PM	#3
mille239 Premium Member Join Date: Nov 2003 Location: Harrison Twp., MI Posts: 1,644	I do mine every year, but the Mfg. recommends every 6 months. I think that is a little much, but if you track your readings, you'll know when it starts to slide in one direction ort the other. (I'd replace your probes every 2.5 to 3 years as well) __________________ -Blair Disclaimer: No trees were harmed in the creation of this post, though a significant number of electrons may have been inconvenienced. Current Tank Info: 120 SPS reef in progress, 120 mixed reef, currently being completely rebuilt)

07/29/2008, 12:40 PM	#2
sps1-2-b Registered Member Join Date: Nov 2007 Location: Anaheim, CA Posts: 1,248	I've read that you're suppose to, but I haven't recalibrated mine for a year either. I'm tagging along to see if it's absolutely necessary. Thanks.

07/29/2008, 02:26 PM	#4
The Saltman Moved On Join Date: Mar 2005 Location: Northwest Ohio Posts: 1,642	The standard I heard on ph probes is after 1 year to replace. Lab grade ph probes could probably go 1.5 to 2 years.

07/29/2008, 03:34 PM	#5
MattAndKim Registered Member Join Date: Jun 2008 Location: Ann Arbor, MI Posts: 161	Will the pH meters you are using display probe nernst slope? If they won't you can't really have any idea of the drift the probe has experienced. If they do, compare the slope to the allowable specification given by the probe manufacturer. Probes with bad slopes can sometimes be cleaned with enzymatic cleaners, isopropyl alcohol, and other solvents without damage. Probes with low slopes can sometimes be regenerated with dilute acid solutions. Probes with high slopes are pretty much KIA, i've never heard of a fix for polarization (this results from leaving the probe energized in air). If your slope checks out, but your pH has drifted considerably AND the asymmetry potential is significantly different from when the probe was new, your readings are suspect in my experience. Attempt to regenerate with acid if changing reference fill solution does not fix the problem. The durability of lab grade pH probes depends on the make, the environment, and the fickle nature of pH probes. I personally would not expect a lab-grade pH probe to last this long in a biologic environment but YMMV. This is all based on combination probes, i don't know about split probes. If anyone has questions about care and feeding of pH probes, I have a bit of experience with combo probes in pure and treated water applications. My practice for any important measurement is to immediately calibrate the probe prior to the measurement with buffers brought to the same temperature as the sample. I think for routine monitoring a weekly calibration is sufficient to maintain high accuracy. I would not trust a measurement taken in water flow as fluctuations in flow velocity and temperature will affect the reading.