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May 2006

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Subject:
From:
Lagomarsino Mónica <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Wed, 31 May 2006 09:04:15 -0300
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Jill
We never adjust the pH during the test.
Before doing the preparatory test, we determine de pH of the buffer +
sample, and if pH<6, and preparatory test doesn´t meet, we increase
phosfates concentrations in the buffer, to get at least pH=6; and we use
this modified buffer when we perform adecuability test, so I´m sure to have
an appropiated pH needed for a good recovery.
According to our experience, USP buffer is very weak, and sometimes it isn´t
sufficient to bufferize samples.
When pH>8 (eg. Antacids), we always have obtained good recoveries without
adjustment or modified buffer.
I agree Victor Mencarelli, about the risks of determining and modifying the
pH during routine tests.
Mónica

-----Mensaje original-----
De: The Pharmaceutical Microbiology Forum Email List
[mailto:[log in to unmask]] En nombre de Jill Blythe
Enviado el: Martes, 30 de Mayo de 2006 12:27 p.m.
Para: [log in to unmask]
Asunto: [PMFLIST] pH Adjustments

In light of the harmonized microbial methods that I believe were signed 
off on in November, 2005, what are the thoughts out there on pH 
adjustments of the sample dilution to between 6-8?  Is it necessary to 
make the pH adjustment if we can show by dilution or neutralization, 
recovery of all the challenge microorganisms?

Also, if during validation, a pH adjustment is necessary, how close to 
the pH obtained during validation would one have to be for routine 
testing? Plus or minus 0.2 pH units or just between 6-8?

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------------------
The PMFList (http://microbiol.org/PMFList_info.htm) is operated from
The Microbiology Network (http://microbiol.org) and supported by
our sponsors (http://microbiol.org/sponsor.htm) as a service to
the scientific community.

Please take a second to visit our sponsors' web sites and say thank you for their support of this service.

Accugenix - http://www.accugenix.com

American Type Culture Collection - http://www.atcc.org

ATS Laboratories - http://www.ats-labs.com

Biolog - http://www.biolog.com

Biomerieux - http://industry.biomerieux-usa.com

Dupont Qualicon - http://www.qualicon.com

EMD Chemicals - http://www.emdchemicals.com

EMSL Analytical, Inc. - http://www.emsl.com

Genomic Profiling Systems, Inc. - http://www.genprosys.com

MIDI, Inc. - http://www.midi-inc.com

Millipore - http://www.millipore.com

Pall - http://www.pall.com

NovaTek International - http://www.ntint.com

Raven Biological Labs - http://www.ravenlabs.com

Veltek Associates, Inc - http://www.sterile.com

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The nature of this service is to provide a medium for communication.  The specific statements and endorsements of individuals participating in the discussions are not necessarily those of The Microbiology Network, Inc., the PMF, or the sponsors of the list.

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