Sorry, I was thinking pH strips when the conversation was about pH paper.

I would not recommend using pH paper, but I would pH strips.  There is a major
performance difference.

pH paper is filter paper impregnated with indicator or indicator mixture vs pH
strips incorprate special indicator dyes covalently bound to the cellulose of
reagent paper.

Results on pH strips are highly reproducible.
pH strips have clearly defined colour differences between pH ranges and are
easier to read.
pH strips are highly accurate in weak buffers, subsequent to waiting 5-10
minutes for an indicator on a meter to reach equilibrium.
Strips do not bleed and can be left indefinitely in test medium.
Strips can be used in weakly colored and turbid solutions because they can be
rinsed off.

If I knew about these while I was working in a lab, I would have been using
them.  They would have saved a lot of valuable time.  We sell strips into the
biopharm and biotech industries where measurements are as critical in comparison
as clinical measurements.  One of the applications they use them for are
enzymatic studies besides measuring buffer solutions and other things.

Sometimes a change of mind is hard to come by.  It's all a matter of what you
are comfortable with and in the clinical arena, I am only to familiar with that
feeling.  But I do think as technology progresses, a change of mind might
expediate things a bit  especially where turn-around-time is critical and
staffing is short.

If anyone is interested in trying strips, send me your address.  I can have
samples sent out.   I would be interested to hear about your results and
feelings.

Regards,
Rande Kline, HT (ASCP)
Technical Services
EM Science/BDH.







Gayle Callis <uvsgc@msu.oscs.montana.edu> on 04/03/2000 02:55:51 PM

To:   histonet@pathology.swmed.edu
cc:    (bcc: Rande Kline/EMI/Merck)
Subject:  RE:pH paper vs. meter



Tamara is correct, and at the risk of offending someone, I consider this
neither good advice nor good laboratory technic.

Gayle Callis


>Date: Wed, 05 Apr 2000 17:27:15 -0400 (EDT)
>From: Tamara Howard <howard@cshl.org>
>Subject: RE:pH paper vs. meter
>To: raws43@hotmail.com, Histology listserver
>    <histonet@pathology.swmed.edu>
>
>>Lori Steele from Biogenex just gave a lecture at our State meeting.  She
>>said that a pH meter is not necessary to check the buffer solution for
>>immunohistochemical staining - just use a pH tape with 1.0 intervals.
>>However, it still needs to be done each day you do IHC staining.  I know
>>in our busy lab, it sure is quicker than having to use the meter.
>
>>Becky Scholes
>>Iowa Pathology Associates
>>Des Moines, Iowa
>
>Sorry, but this is not a good idea. Try for yourself - round up some pH
>papers - different ranges and vendors - and try all on one buffer. My bet
>would be that you'll get readings all over the place. Quicker may be nice,
>but reproducibility is really worth the extra time - and it takes less
>than 5 mintues to properly calibrate a meter and check your buffer's pH.
>
>Tamara Howard
>CSHL
>
>
>
>