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Thread: pH meter issues . . .

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    BigBella's Avatar
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    Quote Originally Posted by Not a Number View Post
    Back in the college lab days the probe on the pH meters we used had to be kept wet at all times in a storage solution when not in use. Letting them dry out meant ruining the probe. No idea with current units.
    Warren: it is still the very same situation. After rinsing, the probe is stored with a cap saturated with a pH 4.01 storage solution. it arrived from HM moist and hasn't dried in two years -- including the replacement tip . . .
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

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    Tropical Fish Enthusiast jimscott's Avatar
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    Is it possible that the pH standards are contaminated? I use a pH meter everyday at work and my experience with purified water is that it is not only a little acidic, the readings doesn't stabilize too well. The lack of ions to bind with interferes with stabilizing. We change out or storage solution every week. The probe, when not in use, is kept a small tube of that solution.

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    BigBella's Avatar
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    Quote Originally Posted by jimscott View Post
    Is it possible that the pH standards are contaminated? I use a pH meter everyday at work and my experience with purified water is that it is not only a little acidic, the readings doesn't stabilize too well. The lack of ions to bind with interferes with stabilizing. We change out or storage solution every week. The probe, when not in use, is kept a small tube of that solution.
    It seems unlikely that the standards were an issue, since different lots and brands have been used in the last couple of weeks; and when I had mentioned that freshly-opened distilled water registered pH 7.0, it did fluctuate a tiny amount , as you had described -- in terms of .02 back and forth -- but settled in at about seven. The probe is also stored in a 4.01 solution, recommended by the manufacturer . . .
    Last edited by BigBella; 05-17-2012 at 12:01 PM.
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

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    flasker's Avatar
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    Each pH meter brand has a different setup and working operation. Some "should not use with distilled water" and some store without solution. Read careful your manual and follow it. IMO, don't measure pH 7.0 using distilled water because the meter measures the ion H+ in solution and there's (almost) none ion H+ in distilled water. Use the calibrate solution pH 7.0.

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    mobile's Avatar
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    See the link below, particularly the pH-value chapter, with regards to pH of deionised water. The fact that your meter is reading deionised water as pH 7.0 doesn't necessarily mean it is measuring correctly.

    http://www.lenntech.com/applications...ised-water.htm

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    BigBella's Avatar
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    Quote Originally Posted by flasker View Post
    Each pH meter brand has a different setup and working operation. Some "should not use with distilled water" and some store without solution. Read careful your manual and follow it. IMO, don't measure pH 7.0 using distilled water because the meter measures the ion H+ in solution and there's (almost) none ion H+ in distilled water. Use the calibrate solution pH 7.0.
    I have used pH meters for decades and the manuals have always been followed; there was never an issue with using distilled water with my brand; and I am fully aware of the pH issue with distilled water and its rapid "contamination" by C02 -- and took that into consideration. The water was freshly steam-distilled. I only used it because it was a known quantity in terms of pH and was trying to determine what was wrong with the meter. The probe is also new, within a year . . .

    Quote Originally Posted by mobile View Post
    See the link below, particularly the pH-value chapter, with regards to pH of deionised water. The fact that your meter is reading deionised water as pH 7.0 doesn't necessarily mean it is measuring correctly.
    I realize what you're saying; but my first thought was that the batch of testing media was simply off; and why it was a sudden problem was also a bit of a mystery, since the probe is waterproof and the o-rings perfectly intact and lubricated. Also, I was generally using steam distilled water, though had some deionized on hand -- which also registered pH 7.0 . . .
    Last edited by BigBella; 05-17-2012 at 03:00 PM.
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

  7. #15
    Hello, I must be going... Not a Number's Avatar
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    The meter is probably toast. Did you try a new battery?
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

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    BigBella's Avatar
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    Quote Originally Posted by Not a Number View Post
    The meter is probably toast. Did you try a new battery?
    Yep, you're probably right, though it is still within warranty -- and the company is in SoCal.

    The batteries were the first thing I replaced.



    Thanks one and all for the assistance and suggestions; but it's time to give it its last rights and this topic is as dead as disco . . .
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

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