Where a granted claim directed to a composition defined in an open manner and including the presence of a component belonging to a class or list of compounds in a quantity defined by a range is later amended by limiting the definition of the class or list of compounds, a possible infringement of the requirements of Article 123(3) EPC may be avoided by including in the amended claim a quantitative condition on the limited class or list of compounds and an additional constraint on the total amount of compounds belonging to the broader class or list (point 3.11).