SOP For avoiding cross contamination is described in this post which you can follow in the section of the Quality Assurance Department.

OBJECTIVE
To describe the procedure for controlling and preventing cross-contamination in the dispensing area during operations.
SCOPE
This procedure applies to the production area of the manufacturing facility.
RESPONSIBILITY
Warehouse Officer
Production Officer
QA Officer
ACCOUNTABILITY
Warehouse- Incharge
Manager Quality assurance
Manager Production
PROCEDURE
Always use hand gloves and nose mask while working during dispensing procedure.
Ensure that the AHU’s is ON one hour before starting the activity by recording the pressure differential.
Always clean and disinfect the area before the start of activity. 
Always clean and disinfect the floors, walls, ceiling, doors and other facilities.
Check that the instrument being used are calibrated and within their valid date of calibration.
Always put status label on all equipment, and measuring instrument.
Maintain the dispensing area at positive pressure.
In dispensing area provide the adequate segregation for different materials and equipment's.
Keep the personnel traffic at the minimum in dispensing areas.
Take line clearance every day before starting dispensing activity and after product or batch change over.
Do the dispensing of all raw materials under the reverse airflow hood, started at least one hour before activity.
Keep raw materials separately batch wise and with proper identification label on SS pallet.
Label all sanitizing agents (70% IPA) with collection date and use before dates.
Dispensed one material at a time.
Sanitize washed equipment, utensils with freshly prepared 70% IPA solution, dry and covered with the clean poly bag when not in use.
Ensure that all the materials are opened and placed under reverse laminar airflow during dispensing activity.
Clean the container outside then bring it to the dispensing room.
Clean area after product change over.
Ensure S.S. scoops, spatula etc. are clean and dry.