Bonjour,
Unless using a chiral column, the R & S nitrosamines are not distinguished in the HPLC analysis, therefore the sum of them is determined.
It can be assumed that the two chiral forms have similar reactivity toward nitrosation, therefore they would afford proportional amounts of nitrosamines, that is, the R form is negligible.
From regulatory point of view, there is no distinction regarding the toxicity of these chiral forms.
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