Particulate matter consists of mobile, randomly-sourced, extraneous substances, other than gas bubbles, that cannot be quantitated by chemical analysis due to the small amount of material that it represents and to its heterogeneous composition.

ARL utilizes the light obscuration method for the quantitative determination of particulate matter in injections using a Hach Ultra liquid particle counting system.  This instrument precisely measures particles from small and large volume parenterals as well as fluid used for cleaning medical devices. 

All large-volume injections for single-dose infusion and those small-volume injections for which the monographs specify such requirements are subject to the particulate matter limits set forth for the test being applied, unless otherwise specified in the individual monograph. Excluded from the requirements are injections intended solely for intramuscular and subcutaneous administration.