A dependent claim and the higher-ranking claim on which it depends cannot be grouped into two different groups of inventions (see F‑V, 2.1).
If, however, the higher-ranking claim appears not to be patentable, then the question of whether there is still an inventive link between all the claims dependent on that higher-ranking claim needs to be carefully considered.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/f_v_3_2_3.htm
Date retrieved: 17 May 2021