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Old 01-01-2006, 07:31 PM   #1
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Question about pH calibration solutions

I need the soultion to calibrate a pH probe with. What got me confused when I went to order it is I keep seeing the word "buffer", almost like it's an additive to the water.

Can someone tell me what I need to calibrate the probe with from this list ?

Thx,

Dave
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Old 01-01-2006, 08:07 PM   #2
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I'm not sure if they are premixed or concentrated solutions from that site. Buffer solutions are used to fix the pH at a very specific value which is exactly what you want. Which solution you need depends on the probe you have and which setpoints it uses for calibration. 7.01 is the one closest to where you are going to be testing, so if that is a setpoint for your probe, get that one. If there are two setpoints, it shouldn't matter which other solution you get.
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Old 01-01-2006, 08:16 PM   #3
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Ok, I looked some more and found the actual pH buffers, so I see what I need now.

Why does the calibration solution say buffer .. CD-870858 pH 7.01 Buffer Solution

Thx,

dave
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Old 01-01-2006, 10:01 PM   #4
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apocalypse_gold has already answered your question. a "Buffer" solution is a solution that is buffered to maintain a certain Ph. At work we have fisher brand buffered solutions for our Ph probes. Ph 4, 7, and 10. they also sell packets that are mixed with DI water to form the solution.

If the solution wasn't buffered you would not know the exact Ph of it. ie carbonic acid will decrease the Ph of the solution and therefore the calibration curve for that instrument would be in question.

Normally you have to have 2 solutions inorder to calibrate a Ph probe. The two should be bought that closest match what you will be measuring.

Oh, and one other thing. the solutions should be at a set temperature when calibrating the probe. the ideal temp is 25 +/- 5 degrees C.

In order for me to say which solution you need i have to know what probe and what instrument it is connected to.

but from the sounds of it all you need is the ph 10.01 and 7.01 buffer solutions. It would be a good idea to get the storage solution also. If not, the potentials of the Ph probe will get clogged up and render the probe useless. you can make your own storage solution if you have access to KCl. just add some KCl to the Ph 7 buffer and you will be all set.
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Old 01-01-2006, 10:54 PM   #5
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I use a low/high set of calibration solutions for my probe, i.e. the 4.1 and the 7.1, since they are closest to the pH ranges I test for. As mentioned, it is wise to use two solutions to accurately calibrate.

The solutions are simply known entities that you can trust so you set your machine accurately, and trust the results. If there were household items available that had 99% accurate pH values we could use them, but there are factors that could skew the results so we rely on calibration solutions.
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Old 01-02-2006, 12:40 AM   #6
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A buffer contains stuff that acts as a weak acid and a weak base at a given pH. If you add an acid, it will act as a base; if you add a base it will act as an acid. Thus it manages to maintain a very specific pH (unless you dump in enough stuff to exceed its buffering capacity). Soooo... 4.01 will stay 4.01, 7.01 will stay 7.01, and 10.01 will stay 10.01. If the calibration solutions were not buffered, you would have to calibrate them, which would require a calibrated pH meter, which you don't have because you don't have good calibration solutions, and then you would throw away a perfectly good pH meter. And that would suck.
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