PDA

View Full Version : PH reading


gigiba
12/29/2006, 11:13 AM
I recalibrated the proble last night and it read my tank ph at 7.83.
then, I use my seachem PH test kit and it has color between 8.0 to 8.1.


To make sure the PH probe is working correctly, I reclibrated again with another new PH4 and PH10 fluid bag. It turned out the same reading.

To make sure the seachem test kit is correct, I use the reference test sample that came with the kit and the color read out is right on what it should. So, the test kit is working correctly.

Now the real question....which should I trust?

RobbyG
12/29/2006, 12:42 PM
I assume since it's pH 4 your using that this is Aquatronica brand Calib Fluid? Therefore it should be an accurate calibration, but that all depends on the age of the probe. If in doubt get a pouch of 7.0 pinpoint fluid and dunk the Calibrated probe into that. If it reads 7.0 then you pretty much know that the pH probe is working ok. My gut feeling is that your pH probe has reached the end of it's life. How long have you had it? Have you ever cleaned it with Ro water?

gigiba
12/29/2006, 01:28 PM
I just came back from my LFS and they tested the PH. It is at 8.1.
so my ph probe is not getting a correct value. The owner of the fish store told me if my PH is at 7.8, I would see alge growing like crazy and my fish will start to stress and die. At this time, my tank looks good without algea attack and my fishes are doing great and eat like a pig.

I got my controller package back in September and I setup my tank in Nov. So, I only use the probe for a bit more then a month. When I do calibration, I use tap water to rinse the probe. Because, I read one of the thread that you suggested -- only Tap water no RO water.

what should I do now?

gigiba
12/29/2006, 01:31 PM
<a href=showthread.php?s=&postid=8850029#post8850029 target=_blank>Originally posted</a> by RobbyG
I assume since it's pH 4 your using that this is Aquatronica brand Calib Fluid? Therefore it should be an accurate calibration, but that all depends on the age of the probe. If in doubt get a pouch of 7.0 pinpoint fluid and dunk the Calibrated probe into that. If it reads 7.0 then you pretty much know that the pH probe is working ok. My gut feeling is that your pH probe has reached the end of it's life. How long have you had it? Have you ever cleaned it with Ro water?

PH4 and PH10 fluid are AQ brand.

BTW- Can I use other brand PH fluid for calibration? also, can I use other brand of PH probe for AQ controller?

RobbyG
12/29/2006, 03:02 PM
<a href=showthread.php?s=&postid=8850306#post8850306 target=_blank>Originally posted</a> by gigiba
PH4 and PH10 fluid are AQ brand.

BTW- Can I use other brand PH fluid for calibration? also, can I use other brand of PH probe for AQ controller?

Yes you can use Pinpoint 10 &7 fluid. I personaly prefer the AQ 4 and 10 since it gives a greater calibration spread.

Right now I am using a Pinpoint pH probe and it works great.

gigiba
12/29/2006, 06:10 PM
Thanks RobbyG !!! Great info.

AQ -- I only used this probe for 1.5 month and it read low value when comparing with Seachem PH test kit and my LFS PH test.

Please let me know how to troubleshoot this.

Note: I re-calibrated 2 times and used all the PH4 and PH10 fluid bags that I bought from AO.

ik2vov
01/05/2007, 03:19 AM
Hi gigba,

are you calibrating the probe with pH 4 and 10?

If you use the probe to test the calcium reactor, you have to use the 7 and 4 calibrating fluids, if you test the tank water you have to use the 7 and 10 fluids.

You can use any pH calibrating fluid, it' important to have certificated fluids.

When you calibrate the probe be sure to clean it before using into the fluid (you can clean the probe firs with water,never r.o. water, and then with a clean piece of paper, the one used to clean the kitchen), then you can put the probe into the fluid.

Bye

gigiba
01/05/2007, 10:32 AM
Yes, I am using 4 and 10.

I will try 7 and 10.

When you said certificated fluids, how do we find out that info from the packaging? I can get Pintpoint PH fluids a lot cheaper in my area.

Captain Quirk
01/05/2007, 12:04 PM
<a href=showthread.php?s=&postid=8901797#post8901797 target=_blank>Originally posted</a> by ik2vov


When you calibrate the probe be sure to clean it before using into the fluid (you can clean the probe firs with water,never r.o. water, and then with a clean piece of paper, the one used to clean the kitchen), then you can put the probe into the fluid.

Bye

Curious: I've never heard anything about NOT using RO water for rinsing your probes in between calibrations.

???

RobbyG
01/05/2007, 01:45 PM
<a href=showthread.php?s=&postid=8904585#post8904585 target=_blank>Originally posted</a> by kernelangus
Curious: I've never heard anything about NOT using RO water for rinsing your probes in between calibrations.

???

Thats why I was asking him. Ro Water will destroy the glass membrane. It somehow leeches into the glass and does damage.

ik2vov
01/07/2007, 04:12 PM
<a href=showthread.php?s=&postid=8903782#post8903782 target=_blank>Originally posted</a> by gigiba
Yes, I am using 4 and 10.

I will try 7 and 10.

When you said certificated fluids, how do we find out that info from the packaging? I can get Pintpoint PH fluids a lot cheaper in my area.
With certificated fluids I mean to use fluids made fro this usage, I prefer to use single use calibration fluids so to have them always fresh. You can use every brand fluids, it's just important that you are sure they are good.

Bye

gigiba
01/11/2007, 12:18 PM
I recalibrated the AQ PH probe with pinpoint 7 and 10 fluid and same result. it read about 7.74. I bought a pinpoint PH probe to use it with AQ. After I calibrate the Pinpoint PH probe, it read about 8.0. My seachem test kit showed around 8.1.

conclusion- AQ PH probe is way off (bad probe?) and pinpoint is close to the seachem test kit, but still 0.1 off.

Is there something to do with PH module? (it feels warm when I touch the PH module. normal?) how can I get a accurate PH reading from the probe? I am thinking to purchase another Ph module to work with my calcium reactor, but this is holding me back!!

RobbyG
01/11/2007, 01:37 PM
pH probe should not be warm, sounds like something is wrong. I use a Pinpoint pH probe and it works really well, I get a much more accurate and stable reading.

Captain Quirk
01/11/2007, 01:44 PM
<a href=showthread.php?s=&postid=8955395#post8955395 target=_blank>Originally posted</a> by RobbyG
pH probe should not be warm, sounds like something is wrong. I use a Pinpoint pH probe and it works really well, I get a much more accurate and stable reading.

So do I. The AT probe was slow and erratic at best. I still have it submerged in my sump; for some reason, I haven't thrown it out. Perhaps I ought to anyway.. Not like I'm ever gonna use it.

See? We DO agree on some things!

Also, IIRC, the PP is cheaper, is it not?

gigiba
01/11/2007, 02:48 PM
<a href=showthread.php?s=&postid=8955395#post8955395 target=_blank>Originally posted</a> by RobbyG
pH probe should not be warm, sounds like something is wrong. I use a Pinpoint pH probe and it works really well, I get a much more accurate and stable reading.

The "PH module" is warm. (not the probe.)

Captain Quirk
01/11/2007, 03:39 PM
<a href=showthread.php?s=&postid=8956013#post8956013 target=_blank>Originally posted</a> by gigiba
The "PH module" is warm. (not the probe.)

D'oh! I didn't read your post, only the one above it.

Most sincere apologies...

Don't recall that my module is warm; I'll check when I get home. If it is, I'll post back. Otherwise, yours is a little heater as well as a handy-dandy pH interface module... Bonus points!

You mean warm or WARM? A little bit of heat sounds normal (or at least feasible).

???

gigiba
01/11/2007, 04:00 PM
<a href=showthread.php?s=&postid=8956501#post8956501 target=_blank>Originally posted</a> by kernelangus
D'oh! I didn't read your post, only the one above it.

Most sincere apologies...

Don't recall that my module is warm; I'll check when I get home. If it is, I'll post back. Otherwise, yours is a little heater as well as a handy-dandy pH interface module... Bonus points!

You mean warm or WARM? A little bit of heat sounds normal (or at least feasible).

???

It is ok.

I don't know how to tell you if it is warm or WARM. Lol...
It is not hot for sure.

ik2vov
01/12/2007, 01:44 AM
gigba, the probe is a new one?

Before calibrating the probe, did you leave it in sump for one week to let it stabilize?

Bye

gigiba
01/12/2007, 09:34 AM
the probe is new and only few month old.
I bought it back in September and started to use it in November.

When I started to use it, I put in sump for few weeks because I didn't know that I have to calibrate a new ph probe. After I read some of the treads here and then I tried to calibrate the ph probe. That's like few weeks later.

First calibration went smooth and the reading is good. But, after a month or so, it went from 8.1 to 7.8. So, I recalibrate again and it stay around 7.8. As you can see from the thread, I tried to recalibrate many times and it gave me about the same reading.

(light on ~7.9, light off ~7.74)-usually is ~7.8.

It seems to me that it is working, but constantly off. I should add about 0.4 to the reading then it will be good. But, this is a new probe and it should give me a good solid reading.

gigiba
01/13/2007, 03:55 PM
I am using pinpoint PH probe and now I am getting 8.0 to 8.1 with light off and on.

So it is not the module for sure. It is the probe.

RobbyG
01/13/2007, 04:46 PM
I love the AQ controller but they need a new supplier for pH and Salinity probes. Not really a problem since everything is sold separately but it would be nice if you could buy the whole package and get probes that match the quality of the controller.

gigiba
01/15/2007, 01:49 PM
So, is my PH probe from AQ still under warranty??

Captain Quirk
01/16/2007, 01:29 PM
<a href=showthread.php?s=&postid=8988461#post8988461 target=_blank>Originally posted</a> by gigiba
So, is my PH probe from AQ still under warranty??

Good question. I know the controller is 2 years, but what about the individual components? I can't imagine a probe would have the same warranty, as they only have a life of ~ a year...

???

Powerbars? pH, PC interfaces?

RonBuck
01/16/2007, 05:27 PM
<a href=showthread.php?s=&postid=8901797#post8901797 target=_blank>Originally posted</a> by ik2vov
Hi gigba,

are you calibrating the probe with pH 4 and 10?

If you use the probe to test the calcium reactor, you have to use the 7 and 4 calibrating fluids, if you test the tank water you have to use the 7 and 10 fluids.

You can use any pH calibrating fluid, it' important to have certificated fluids.

When you calibrate the probe be sure to clean it before using into the fluid (you can clean the probe firs with water,never r.o. water, and then with a clean piece of paper, the one used to clean the kitchen), then you can put the probe into the fluid.

Bye

This is opposite of what Derrik from Aquatronica told me. He specifally told me that 10 and 4 is ok to use. Also, that using these fliuds to calibrate would help eliminate the "Unable to Calibrate" error. Because it gives the user a wider window between the two levels when the probe is off more than it should be.

RobbyG
01/16/2007, 05:58 PM
Ron that was what I heard also.
I am not sure if Gilbertos first sentence was a Question implying you should use 4 and 10 or he was implying it was bad to use 4 and 10.

gigiba
01/20/2007, 10:25 PM
still waiting for an answer.....BUMP ^^^

ik2vov
01/22/2007, 04:33 AM
Hi RonBuck,

thanks for your replay, I'll immediately ask to Derrek because i usually use with all my 4 pH units the same directions.
I'm using 2 Aquatronica pH probes (one in the tank and another in the reactor) and have a pH value that is quite equal to the other 2 pH controllers (one is a Hanna inst. with Hanna probe and the other is Ruwal with Hanna probe) i have in tank.

As i wrote before, I use to calibrate my probes with pH 7 and 10 when I use the probes in tank, when I use the probe in the calcium reactor i calibrate with pH 7 and 4.

For me the major problem of the Aquatronica pH probe is that it's necessary a long time to stabilize (1 week) when it's new or when you repose it, but to me after this initial period always worked well.

Bye

gigiba
01/22/2007, 11:55 AM
So, what's the warranty on the Ph probe? I calibrated with 4, 7 and 10. it still read ~7.8 and never go over 8.0. My Test kit and pinpoint ph probe are reading the same as well as the ph test from my LFS.

gigiba
01/27/2007, 08:54 PM
So, do I get a replacement ? or I should just dump the PH probe into trash can and forget about it?
:rolleyes: :rolleyes: :rolleyes:

Aquarium Obsessed
01/28/2007, 06:43 AM
Gigiba,

Please return the defective probe to:

Aquarium Obsessed
250 Bayview Drive
Unit #5
Barrie, Ontario
L4N 4Y8
CANADA

We will send out a replacement as soon as we receive it.

thanks,
Aquarium Obsessed

ik2vov
01/29/2007, 04:52 AM
Warranty on probes is 6 mounts from date stamp on the probe or 6 mounts from the sales invoice date.
Warranty on the electronic parts is two years from the date stamp on the product.

Bye

gigiba
02/01/2007, 11:27 AM
Thanks AO for the great service !!!

Captain Quirk
02/01/2007, 01:40 PM
I'd be curious to know if you would do a cross-ship (with deposit, of course) in situations like this.

???

<a href=showthread.php?s=&postid=9094761#post9094761 target=_blank>Originally posted</a> by Aquarium Obsessed
Gigiba,

Please return the defective probe to:

Aquarium Obsessed
250 Bayview Drive
Unit #5
Barrie, Ontario
L4N 4Y8
CANADA

We will send out a replacement as soon as we receive it.

thanks,
Aquarium Obsessed

RDS
02/04/2007, 05:45 AM
As Robby already mentioned the probes (ph, conductivity) are the weak points of this computer.
Conductivity: I have to clean it every 2-3 days to get accurate values
Now my pH-probe is dying. Up to now, I calibrated it with pH-buffers 7 and 9,2 without any problems. Today I tried to calibrate again and got the "unable to calibrate..." error :( Afterwards I calibrated it with pH 4 and 9,2 --> the calibrations was successful (RonBuck explained it already).
The probe is only 8 month old!
My next pH-probe will be a "real pH-glas-electrode" (with KCl) and not a gel-electrode like the original AQ!

By the way: You can use r.o water to clean the probe between the calibration! For accurate measurements you have to use r.o. water (laboratory,...)! But you must not store it in r.o. water --> you have to use the same electrolyt as in the probe (for example 3M KCl).

RobbyG
02/04/2007, 09:31 AM
<a href=showthread.php?s=&postid=9154894#post9154894 target=_blank>Originally posted</a> by RDS

My next pH-probe will be a "real pH-glas-electrode" (with KCl) and not a gel-electrode like the original AQ!

By the way: You can use r.o water to clean the probe between the calibration! For accurate measurements you have to use r.o. water (laboratory,...)! But you must not store it in r.o. water --> you have to use the same electrolyt as in the probe (for example 3M KCl).

RDS do you have a link for more info on this probe?
Are you saying that the probe with KCl can be cleaned with RO? If you are saying that regular pH probes can be, that would go against the statements by probe manufactures who say that the probes must not be cleaned with Ro.

RDS
02/04/2007, 10:34 AM
For example a IKS-probe IKS-probe (http://www.iks-aqua.com/html/engl/zubehoer.php) . Generally speaking: You can use nearly every probe - I've access to "professional probes" (laboratory) but with wrong connectors - no problem: I'll replace them with an BNC-connector and I'm sure it will work accurately enough.

Believe me, you have to use RO water to rinse the buffer (or every other liquid) of the electrode, because you need to wash away every ions (ionic compounds), molecules,... (contamination of the next buffer, liquid,...). In a laboratory you use also very pure water (high quality water). Generally, the membrane has only contact with water for a short time!

I think the manufactures mean that you must not "really clean" the electrode with ro water (to get rid of solid dirt,...). In this case you have to use low concentrate HCl (with pepsin) and so on.

You have to differentiate between short rinsing and cleaning.

RobbyG
02/04/2007, 01:04 PM
I don't know, what is what but I can tell you I cleaned my first AQ probe with Ro and it only lasted about 9 months and died. Could be that they are just poor quality probes on the other hand it could be the Ro.

RDS
02/05/2007, 10:32 AM
I tell you, you can use ro water without any problems (it's the probe) :) - I'm working with (high-end) ph-probes in my job!

Here some exemplarily links found with google:
http://delloyd.50megs.com/moreinfo/ph.html
http://www.eutechinst.com/techtips/tech-tips26.htm

(Search on this sites for "distilled water" (it's purer than ro-water))

RobbyG
02/05/2007, 01:25 PM
<a href=showthread.php?s=&postid=9163945#post9163945 target=_blank>Originally posted</a> by RDS
I tell you, you can use ro water without any problems (it's the probe) :) - I'm working with (high-end) ph-probes in my job!

Here some exemplarily links found with google:
http://delloyd.50megs.com/moreinfo/ph.html
http://www.eutechinst.com/techtips/tech-tips26.htm

(Search on this sites for "distilled water" (it's purer than ro-water))

RDS I am a bit confused. The first link does refer to the use of distilled water to try and rejuvenate a dying probe, but I am not sure who wrote the article and his level of Knowledge.

The SECOND article clearly states

Under Cleaning:

"For general cleaning: Soak the pH electrode in 0.1 M HCl or 0.1 M HNO3 for 20 minutes. Rinse well in tap water "

ALSO

Under Conditioning:

"After removing the electrode from soaking bottle or protective cap at the bottom of sensor, place the electrode in a clean container containing one of the liquids i.e. 4.0 M KCl or pH 7.0 buffer. Soak electrode for 30 minutes if left dry. NOTE: Never condition the electrode in distilled water or deionised water - long term exposure to pure water will damage the special glass membrane.
After conditioning the sensor, rinse the electrode with distilled or deionised water. The electrode is ready for calibration and measurement"


From what I have read, "Conditioning" is a one shot procedure that you do on a new probe or one that has just been refilled.
From what I am reading, it does not seem as though Ro or Distilled water should ever be used on the probes for regular cleaning. I would normally say this is a 50/50 argument but the literature from Pinpoint and other manufacturers warn against using Ro water for cleaning probes.

This whole thing is a bit confusing, but for now, I am still avoiding Ro water until I can read a more detailed reason as to why I should use it when Pinpoint says don't.

RDS
02/06/2007, 12:19 PM
You are hard to convince ;)

RDS I am a bit confused. The first link does refer to the use of distilled water to try and rejuvenate a dying probe...
I can’t find the part where you should use dest. water for a long time to rejuvenate a dying probe, but in special cases it’s true, you can do it and at times we (job) also do it - but you have to know how and with which electrode (if you knew what we do with our electrodes, you would...:D) . But generally don’t do it!!!


but I am not sure who wrote the article and his level of Knowledge.
The level of knowledge is ok and correct - it’s “ph- general knowledge”

RobbyG, don’t make it so complicated ;): You must not use dest/ro water for “real-cleaning” but you can/*have to use dest./ro water to rinse of the buffers,… from the electrode not to contaminate the next solution. *“Have to”: every laboratory in the world have to use dest./ro water, because tap water isn’t “pure” enough (we are measuring the pH with a accuracy up to 3 decimal places - tap water is forbidden in an analytical laboratory!). And don’t forget, the electrode has only contact for some seconds.

This whole thing is a bit confusing, but for now, I am still avoiding Ro water until I can read a more detailed reason as to why I should use it when Pinpoint says don't.
After all, you can use tap water, it’s good enough for salt water! I wanted only to point out, that it’s not a disaster to use ro-water to rinse the probe!

Now I want to "shock" you :D (read it and forget it afterwards - I only want to show you, that pH-electrodes/measurement are not an easy field):
1. We even have (special) glas-electrodes to measure the pH of dest./ro/high quality water.
For your information (one of the biggest manufactures of prof. electrodes): http://www.electrodes.net/splash.html?language=en --> Sensor product guides --> pH electrodes --> pure and ultra pure water --> inLab433 (read the pdf) :) (membran glas: LoT only means "low membrane resistance" contrary to the nomal acid/base electrode with HF glas (low conc. hydrofluoric acid resistence))

2. Have a look at the file I attached (it's from another big manufacturer (Metrohm))


By the way (from the first article) - 2 probe types:
Non-refillable type (Aquatronica)
Permanently sealed with gel fill solution.
Rugged, but has a shorter life, easy to use and inexpensive.

Double junction electrode (should be the better choice for salt water)
Two chambers. Upper chamber has silver chloride wire/KCl saturated with AgCl, and lower chamber has a KNO3 electrolyte solution.
Designed to work in same applications as for the calomel electrode, but at higher concentrations of problem materials.

(Calomel combination electrode Has KCl wire and mercuric chloride, with a KCl reference electrolyte. No silver wire. Refillable.
Fill solution is less reactive, does not react with sample, but is temperature sensitive.
Designed to work in solutions containing proteins, organics, low ion activity, tris buffers and heavy metals.)

RobbyG
02/06/2007, 02:20 PM
Ok RDS I have to admit you know this stuff a 100% more than anyone else I have found on the forum. You are now the official probe Guru :)

Let me make sure I have this all straight.

1.Clean the probe before calibration with Regular water. Especially if you plan to soak it.
2.Calibrate Probe in 10.0
3.Rinse probe with Ro Water (Can it be Ro/Di or just Ro ?)
4.Calibrate probe in 4.0 or 7.0
5.Rinse probe again with Ro

Is this the way you would recommend ?

The Double junction electrode probe sounds very interesting,. Have you ever tried one on the AQ? If so how much $$ are they on average.

Thank you for the attached file, it was a very good read and clarified the Ro point and the Glass membrane penetration and how it works. I will definitely be keeping that jpg on hand.

Also, thanks for enlightening me to the proper probe cleaning method.

RDS
02/07/2007, 12:27 PM
Ok RDS I have to admit you know this stuff a 100% more than anyone else I have found on the forum. You are now the official probe Guru

Thanks :) - but that's not worth mentioning.

Let me make sure I have this all straight.

1.Clean the probe before calibration with Regular water. Especially if you plan to soak it.
2.Calibrate Probe in 10.0
3.Rinse probe with Ro Water (Can it be Ro/Di or just Ro ?)
4.Calibrate probe in 4.0 or 7.0 5.Rinse probe again with Ro

Is this the way you would recommend ?

This is a suitable way, but if you don’t want to throw away the first buffer after measuring, you should also use ro water (you can use a buffer a few times - good enough for our accuracy needs).

So, I would also use Ro for 1 - with that change it’s perfect :)

I’ve attached a file with an exact explanation of conditioning, cleaning,… of a gel-electrode (it’s the same for the double junction electrode (combination electrode)). If you have access to the following chemicals, you can prepare following cleaning-solution: 1% pepsin / 0,1 M HCl.

BTW: A gel-electrode (like Aquatronica) works also with a KCl-electrolyte but this electrolyte is embedded in a gel/polymer (cyanoacrylate, cellulose,… basis). Advantage: You don’t need refill the electrode, a little bit cheaper / Disadvantage: Slow and when the electrolyte is empty, the probe is dead – you can’t refill it (--> shorter lifetime).

Ro water is pure enough!


Have you ever tried one on the AQ? If so how much $$ are they on average.
No, I haven’t tried one yet, because my lab.-electrodes don’t have BNC-connectors. I’ll buy a connector this weekend and change it --> I’ll keep you informed.
But every normal combined electrode will work for sure (they are the actually “equal”).

For example, the price for the iks-electrode here in Europe is ~ 130$ (special lab. electrodes are more expensive)

Thank you for the attached file, it was a very good read and clarified the Ro point and the Glass membrane penetration and how it works. I will definitely be keeping that jpg on hand.

Also, thanks for enlightening me to the proper probe cleaning method.

You’re welcome

RobbyG
02/07/2007, 04:48 PM
Thanks for all the great info and please keep us up to date on the Lab electrode.

RDS
02/20/2007, 12:04 PM
Hi RobbyG,

ok, I’ve replaced the gel-electrode by a glas-electrode and it works great. I was a little bit surprised about the accurate reading because it wasn’t so easy to attach a bnc connector (I had to do a little work-around) and I worried about electrical influences.

RobbyG
02/20/2007, 01:26 PM
Thats great. Do you have a link to the Glass-electrode you used?

RDS
04/02/2007, 11:45 AM
Sorry for the long delay!

No, unfortunately I've no link (it's a "normal" electrode) - I can't find the brand name.