You can restrict the use of an apostrophe by using the server validation for Restrict Content. For Don't Allow enter an apostrophe ' then choose includes from the dropdown list and add it with the plus button.
The function call on the page will look like this:
$WAFV_Errors .= WAValidateRT(((isset($_POST["email"]))?$_POST["email"]:"") . "","'|'",true,3);