PMFLIST Archives

October 2009


Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
"Tsuchiya, Masakazu" <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Wed, 14 Oct 2009 17:31:10 -0400
text/plain (105 lines)
Dear Mohammed Yousffi,

I just calculated the amount of possible endotoxin in your sample.
The amount of 18 ppb is 18 ng/mL of total carbon.  Assuming endotoxin is
about 10% weight of the total carbon, the concentration of endotoxin in
your sample is 1.8 ng/mL.  The potency of purified endotoxin is about
5-10 EU/ng, but in this case, endotoxin is naturally occurred endotoxin.
Assuming the potency of the endotoxin is 1 EU/ng, the endotoxin activity
in your sample can be 1.8 EU/mL.  So it was possible that you observed
0.65 EU/mL endotoxin in a water sample with 18 ppb TOC.

I know it is too much assumption, but if the sample contains mostly
endotoxin, endotoxin can be detected in a sample that shows under the
detection limit of TOC.  The LAL test detects ppt order of endotoxin.

I am sorry for not providing any useful information to solve your
It is just for your information.

Best regards,

KAZ Tsuchiya
Masakazu Tsuchiya, Ph. D.
Senior Research Scientist
Endotoxin and Microbial Detection
Charles River
TEL: 843-766-7575
FAX: 843-766-7576
E-mail: [log in to unmask]
Experience the new 
Accelerating Drug Development. Exactly.

Notice - This email and any files transmitted with it are confidential
and may contain privileged and/or proprietary information. You must not
disclose this message to another party without Charles River's express
written consent. If you are not the intended recipient you must not
copy, distribute or use this email or the information contained in it
for any purpose other than to notify us. If you have received this
message in error, please notify Charles River immediately, and delete it
from your system.

-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List
[mailto:[log in to unmask]] On Behalf Of Mohammad Yousffi
Sent: Thursday, October 08, 2009 10:47 AM
To: [log in to unmask]
Subject: [PMFLIST] Endotoxin In RO system but TOC is low

Can someone explain to me why you would see high Endotoxin (0.65 Eu/mL)
in a USP purified RO water system (With RO membranes and an EDI system)
when the TOC is low (~ 18 ppb)?

We installed new membranes as part of our Preventative maintenance and
initially we saw high TOC (>300 ppb) and then it dropped after draining
the storage tank. Now its in normal range but we see high Endotoxin in
the water.

Thanks in advance!
Mohammed Yousffi
[log in to unmask] 

The PMFList ( is operated from
The Microbiology Network ( and supported by
our sponsors ( 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 -

American Type Culture Collection -

Applied Biosystems, MicroSeq Microbial ID System -

BD Diagnostic Systems -

Biolog -

Biomerieux -

EMD Chemicals -

MicroBioLogics, Inc. -

Millipore -

MODA Technology Partners -

Pall -

NovaTek International -

Rapid Micro Biosystems -  (formerly GPS)

Raven Biological Labs -

Veltek Associates, Inc -

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.