Re: [Killietalk] pH (was Re: copper leaching from new plumbing)

[LeeH920226 at aol_com]

In a message dated 2/16/07 1:11:34 AM, whuntley at verizon_net writes:

<< 
You might just have a very poor or damaged meter, Lee.

 >>

Wright,
    I was a technical leader of a study at DuPont which ran an experiment 
with a group of trained laboratory technicians to determine the sources of error 
in pH measurements. They each measured samples we provided them and used their 
own pH meters in the manner they normally used them. Results were dramatic. 
Unless they calibrated the meter just before using them, the results were all 
over the map. These were with mostly laboratory bench model pH meters -- all 
fairly expensive from reputable manufacturers. Only those who calibrated the 
meter before the test gave results close to the right value. These test solutions 
were buffered solutions. Calibrating once a day was not sufficient either. 
Storing the electrode in pH 4 buffer is also important. Try checking your meter 
and see. I know my pH meters, I have two, are the same way. TDS meters on the 
other hand never seem to drift, unless the batteries are run down.

Lee Harper
Media, PA
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