Pimpoint Calibration Fluids

[Andy]

Hello

I just recalibrated my Pinpoint pH Monitor "again" and got a reading of 8.07. This was shortly after adding a buffer to my system that claims to raise pH to 8.3. Then I measured my pH with 2 titration type test kits (add 2 drops and compare colour)and got a reading of 8.3-8.4 with each. Makes me wonder whether my calibration fluids are off. Can anyone provide their insight to this? The reason I'm concerned is that my Pinpoint monitor registed a pH of 7.6 for my system this morning. As you can imagine, I was pretty freaked out. Was my pH really at 7.6 or was it 0.3-0.4 pH units higher? All my corals seemed fine.

Thanks,

Andy

[Ironreef]

If you calibrated it with #4 and #7 fluid I would use that before the color on a test kit.Your eyes can fool you.its normal for ph to dropare you using a cal reactor. I belive they tend to keep ph a little lower.But if your using a buffer your probaly not. Just use more a little at a time.

[stevenc64]

Andy,
I had the same concern with the pinpoint calibration solutions. Check out this link, I think you will find it very helpful. Look for the article on "pH meter calibration." You can use a borax solution to check your calibration. It is dirt cheap and works great. HTH http://fpage1.ba.best.com/~cbingman/index.htm
Steve

[This message has been edited by stevenc64 (edited 08-13-2000).]

[This message has been edited by stevenc64 (edited 08-13-2000).]

[Snailman]

www.omega.com (http://www.omega.com) has 4.0, 7.0 and 10.0 NIST traceable ph calibration solution by the pint bottle for about $4 each. It is better than the hobby stuff and cheaper also. :)

[plankton]

Andy, several comments.

1) ph 10 cal standard solutions tend not to be stable, but I prefer to use them since I get get two points around my target pH: 7/10.

2) You should be able to get to within 0.01 of the std ph solution (taking temp correction to consideration). IF you cannot get your probe to "reach" up to 10 or down to 4 then you may have a bad probe.

A probe can fail for a number of reasons: clogged junction, cracked inner tub, etc.

What calibration solutions are you using. And, did you attempt to reuse them? It is possible to successfully reuse them within a short period of time and if you are care about using DI water to rinse the probe tip, etc. Don't recommend it though.

------------------
eplankton.homepage.com (http://eplankton.homepage.com)

[Staceon]

Is tip of probe clean?

[gas4544]

The calibration solutions mentioned by snailman are found at http://www.omega.com/ppt/pptsc.asp?ref=PHA4_7_10

Pollard water has a good prices at http://www.pollardwater.com/emarket/pages/ph_buffers.asp

[bzipkin]

I tried what you sujest only with R.O. to wash off the probe and i also tap the
probe very gently on a piece of paper towel the remove any water.
However i get 2 different readinds , 1st is if i swirl the probe in the pouch i get a
readind of .25 above the readind were i do not swirl the probe which is correct .
To swirl or not to swirl.