how to write orderby in join query with where clause in codeigniter

1public function getLatestStatus($data, $userid)
2	{
3		$this->db->select('
4				S.shipment_id,
5				S.added_on,
6				S.waybill_number AS waybill,
7				s_status_logs.updated_on,
8				s_status_logs.status_location,
9				s_status_logs.px_statuscode,
10				s_status.status_title,
11				s_status_logs.status_description AS remark,
12				transitpartner_name
13			');
14		$this->db->from('shipments as S');
15		$this->db->join('users', 'users.user_id=S.user_id', 'left');
16		$this->db->join('master_transit_partners as mtp', 'mtp.transitpartner_id=S.fulfilled_by', 'left');
17		$this->db->join('shipments_status_logs as s_status_logs', 's_status_logs.shipment_id=S.shipment_id', 'left');
18		$this->db->join('shipments_status as s_status', 's_status.status_id=s_status_logs.px_statuscode', 'left');
19		$this->db->where('S.waybill_number', $data);
20		$this->db->or_where('S.shipment_id', $data);
21		$this->db->where('S.user_id', $userid);
22		$this->db->limit(1, 1);
23    $this->db->order_by('S.shipment_id', 'desc');
24		$query = $this->db->get();
25		return $query->result_array();
26	}