RE:pH paper vs. meter

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From:"J. A. Kiernan" <>
To:Histonet <>,
Content-Type:TEXT/PLAIN; charset=US-ASCII

On Fri, 7 Apr 2000 wrote:

> pH strips are highly accurate in weak buffers, subsequent to waiting 5-10
> minutes for an indicator on a meter to reach equilibrium.

   If a pH meter takes 5-10 minutes to give a steady reading, whatever
   it's immersed in, it needs a new electrode. The only exception
   would be an older meter that uses an electrometer tube (=valve) in
   its amplifier (rather than all solid-state electronics). An older
   meter may take an hour or so to "warm up" and it should then be
   left switched on all the time. (Current consumption is almost
   zero.)  Modern meters, including those with "digital" displays,
   do not need a warm-up time. These statements are certainly true 
   of the three electrometer-type and four digital-type pH meters 
   that I've had in my lab over the years. It's the electrodes that
   get broken or wear out - sometimes because of neglect. 

> ...  We sell strips ...
> If anyone is interested in trying strips, send me your address.  I can have
> samples sent out.

  Please!  (Address below)
                                    John Kiernan.  London, Canada.
 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1

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