✔ PDO -> prepare und bindParam funktioniert nicht

$iId=1;
    $opt = array(
            PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8',
            PDO::ATTR_EMULATE_PREPARES, false           
    );
    $oDb = new PDO( $dsn, $usr, $pss, $opt );
    $sQuery = 'SELECT * FROM users WHERE id = :id';
    $oStatement = $oDb->prepare($sQuery);
    $oStatement->bindParam(':id', $iId);
    $oStatement->execute();
    var_dump($oStatement->queryString);

private function loadByMail($sMail, $sPass){
            $sPass = $this->spiceIt($sPass);
            $sQuery = '
                    SELECT
                        id, pre, name, mail, registered, blocked, admin, regdate as rawdate,
                        date_format(regdate, "%d.%m.%Y") as regdate,
                        date_format(regdate, "%h.%i.%s") as regtime
                    FROM
                        user
                    WHERE
                        mail = ":mail" and pass = ":pass"';
            $aParams = array(
                    array('key'=>':mail', 'value'=>$sMail, 'type'=>PDO::PARAM_STR),
                    array('key'=>':pass', 'value'=>$sPass, 'type'=>PDO::PARAM_STR)
            );
            $oResult = $this->getDataResult($sQuery, $aParams);
            $this->setAllMembers($oResult);           
        }

protected function getDataResult($sQuery, $aFields) {
            $this->connect();
            $oStmnt = $this->oDataBase->prepare($sQuery);
            $i=1;
            foreach($aFields as $aField){
                $this->addData('i' . ($i++), $aField['key'] . " -> " . $aField['value']. " -> " . $aField['type']);
                if( isset( $aField['type'] ) ){
                    $oStmnt->bindParam($aField['key'], $aField['value'], $aField['type']);
                } else {
                    $oStmnt->bindParam($aField['key'], $aField['value']);
                }
            }           
            $oStmnt->execute();
            $oResult = $oStmnt->fetchObject();
            $this->addData('result', print_r($oResult, true));
            return $oResult;
        }

WHERE
     mail = "'.$sMail.'" and pass = "'.$sPass.'"';