Sartorius Non-sterile 47 mm Membrane Filters are non-sterile, gridded membrane filters used for colony counting, particle testing, and microscopy. Before usage, the filters first need to be sterilized (e.g. by autoclaving at 121°C). Cellulose nitrate filters (mixed cellulose ester) contain a mixture of cellulose nitrate and cellulose acetate, which assures effective retention combined with high flow rates and optimal colony growth. Cellulose acetate combines high flow rates and thermal stability with exceptionally low adsorption characteristics. Individually wrapped membranes have a 0.45 µm pore size.