Need to allow @ in the URI string

[eluser]Unknown[/eluser]
I'm developing a REST app and one of the capabilities is to be able to register a user. Of course I'll need a valid email address but CI rejects the '@' sign.

I tried changing the $config['permitted_uri_chars'] to these values to no avail:
$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\@\-';
$config['permitted_uri_chars'] = 'a-z 0-9~%.:_@-';
$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-@';
$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-\@';

heck I even tried $config['permitted_uri_chars'] = '' and nothing is changing

Suggestions?