Re: NANFA-- pH kits / chemistry question

John Bongiovanni (bongi_at_cox-internet.com)
Thu, 19 Sep 2002 19:32:07 -0500

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Industry practice is to give chemicals a 5 yr shelf life unless
otherwise indicated. In my lab we routinely give chemicals a 3 yr shelf
life. Storing chemicals cool (< 850) and properly closed and in the
dark will allow them to remain stable. The greatest problem is with
anhydrous salts (subject to water contamination) or solutions that are
subject to microbial contamination. Proper closure prevents the
contamination issues and evaporation.

Evaluate the necessity of having accurate pH readings. If you are
looking for rapid pH swings, any of the methods you mentioned would be
sufficient. Ray, if you are interested in measuring your pond, I think
that strips would be fine. Some of them are pretty precise (unless you
are colorblind ;-) ). The accuracy is consistant allowing for nice
trending. We use digital readers in the lab and calibration is required
upon each use. There are different probes that are easier (and cheaper)
to use than others. The easier ones have less accuracy. Their
inprecision approaches that of the strips. Part# M95833 in the Fisher
Scientific catalogue (www.fishesci.com) is a narrow range strip (pH
6-11), < $15 for a box of 100 and has a sensitivity of 0.2 or 0.3.

John

EELReprah_at_aol.com wrote:

>In a message dated 9/19/02 4:25:19 PM, choupiqu_at_wctc.net writes:
>
><< The electronic meters I have
>
>tried seem to be worthless. They never worked right, and the calibration
>
>solutions I do not rely on, especially if these chemicals also change
>
>sitting on the shelf for any amount of time >>
>
>This is the only reliable method and only if you calibrate regularly -- every
>time you turn it on. The solutions are stable, the meter is not.
>
>Lee Harper
>Media, PA
>/"Unless stated otherwise, comments made on this list do not necessarily
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/ nanfa_at_aquaria.net. To subscribe, unsubscribe, or get help, send the word
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/ nanfa-request_at_aquaria.net. For a digest version, send the command to
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/ For more information about NANFA, visit our web page, http://www.nanfa.org
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