Tutorial - encoding issue

Hello

I'm new to CodeIgniter and I did the tutorial part about creating a news application.
I got an issue at the end with the slug encoding.
If I wrote words with accents (ex: é à è), accents are replaced with ??? in my slug field in my database whereas they are displayed correctly in others fields (title and text). I looked at url_title but there isn't an encode param.



In application/config/database.php, char_set is utf8 and dbcollat is utf8_general_ci


Thanks for help