Q. It is brought down that when reciting the bracha of “Borei Pri Ha’adama” on the karpas one should specifically have in mind that this bracha should exempt the maror that will be eaten later on. (See Mishna Berura siman 473:55)
Question for the rav shlita: The marror is usually lettuce, and lettuce is something that is part of the meal and anyway would be exempted by the hamotzi. (?)
Also, if the marror is eaten 2 or 3 hours after the karpas, due to the lengthy discussion of the Haggada, and the karpas has already been digested (it is past shiur ikul), how will the bracha on the karpas cover the lettuce? There are opinions that the bracha rishona ceases to be effective after shiur ikul has passed!

A. Eishel Avrohom (2: 473) rules that if one forgot and didn’t have in mind to exempt the maror with the ha’adama brocho recited on the karpas, he should not repeat the brocho on the maror, since many Poskim indeed maintain that one does not recite ha’adama in principle on the maror, as it is considered part of the meal. Same would apply if he said bore nefashos after eating karpas.
The required intention on the karpas is only a stringency to comply with all opinions. Still, Piskei Teshuvos (473: n. 139, 475: 7) quotes from the Sheloh and Ya’avetz not to be mafsik and interrupt with idle talk or by exiting the room, between eating karpas and maror. He points out that this is mainly due to the need of maintaining proper decorum and no chatzitza in the kedusha of the night.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a