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Exchange ofthimerosal
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1.
Background
The AOAC validated ELISA assays RIDASCREEN®FAST Milk R4652 (PTM 101501), RIDASCREEN®FAST
Peanut R6202 (PTM 030404), RIDASCREEN® Gliadin R7001 (OMA first action 2012.01) and
RIDASCREEN® Gliadin competitive R7021 (OMA first action 2015.05) use a washing buffer which
contains thimerosal (also known as thiomersal), a mercury containing preserving agent. Since the use
and/or the disposal of mercury-containing liquids is heavily regulated in many countries or even
prohibited in some countries and also in order to protect the environment, R-Biopharm AG would
like to substitute thimerosal in the washing buffer by the mercury-free preserving agent bronidox L.
This preserving agent has also been used at R-Biopharm AG for many years in more than a dozen
ELISA for clinical analysis without any problems.However, an accelerated stability and functional
testing as well as a microbial testing have been performed at R-Biopharm AG for the four concerned
allergen and gluten ELISA.
2.
Procedure of the stability and functional testing
In order to assess whether the use of bronidox L instead of the hitherto preserving agent thimerosal
secures the stability of the washing buffer, an accelerated stability testing has been performed. That
included stability testing of the 10fold concentrate as provided in the test kit as well asof the finally
diluted washing buffer. The accelerated stability testing used a storage temperature of 37°C.
Additionally, two to three control samples were used to assess whether the usage of bronidox L
instead of thimerosal has an impact on the measured concentrations of these samples (functional
testing).