Allowing '@' character in URL

[eluser]Unknown[/eluser]
Ive search around the forums and Google to try and find an answer but cant seem to find out why its not working. I want to allow the '@' character in my URL strings, but when I add it to the permitted characters config and still get "The URI you submitted has disallowed characters.". Heres my current permitted URL config:

Code:

$config['permitted_uri_chars'] = 'a-z 0-9~%.:?@=_\-';