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October 2019


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Mostafa Ibrahim <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Wed, 2 Oct 2019 00:49:04 +0000
text/plain (72 lines)
Hello all,

This is my first time to subscribe to an electronic mailing list, I liked the idea as I had a lot of questions to ask.

Let's start with "Bacterial Endotoxin Testing - Gel clot technique";

1) If I use a 50-test LAL reagent (multi-use) of sensitivity "0.06 EU/ml", I add 0.1ml (100μl) of the test sample to 0.1ml of the LAL reagent, while if I use a single-test LAL reagent of the same sensitivity I add 0.2ml (200μl) of the test sample to the powdered LAL reagent, do I get and assure equal results knowing that the sample size is different (100μl compared to 200μl) ?

2) If I had a sample of an action limit of "60 EU/ml" and I need to test it using a 50-test LAL reagent (multi-use) of sensitivity "0.06 EU/ml", the dilution should be as follows:

A) 1 ml of test sample + 9 mls of LAL water "1:10 dilution"
B) 1 ml of (A) + 9 mls of LAL water "1:10 dilution"
C) 1 ml of (B) + 9 mls of LAL water "1:10 dilution"
D) 0.1ml of (C) + 0.1ml of LAL reagent 

- Why don't we consider step "D" as a dilution step?

- So, if the test showed no gel clotting, then the endotoxin level is <60EU/ml .. but did we use 1ml or only 0.1ml of the sample?

- Does the final "0.1ml" of the sample represent a full "1ml" and is not considered a dilution?


Mostafa Ibrahim
Microbiology Analyst
GSK - Giza Site
[log in to unmask]

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