In this case it would be to trap any particulate matter. Amio can easily precipitate and the .22 micron filter will trap that as well as bacteria air and fungus. If the standard concentration of 900 mg in 500 ml is used...no filter is necessary (will not harm though). All other concentrations require a filter. An add-on filter can be used and should be placed as close as possible to the IV site. If using an in-line filter do not add a long extension set past this that way you trap any particulate matter just before it would enter the patient.