Whatman cellulose nitrate membrane filters have markedly improved flexibility and are designed to tolerate abuse during handling, loading and autoclaving without sacrificing integrity. These membranes are among the strongest of their kind, measured and compared by burst pressure tests. The amount of extractables in membrane filters has become more important with advances in filtration or adsorption techniques. In particular, pharmaceutical, immunological and biomedical tissue culture and trace analysis applications may be affected by high extractables. Whatman cellulose nitrate membrane filters have a low content of extractables, generally below the content of other membranes of a similar type. The nominal pore size of these membranes is tightly controlled due to the advanced manufacturing and control system. In addition, batch-to-batch variation is minimized, resulting in more consistent laboratory results. Membrane filters are normally autoclaved at 121 ° C without compromising integrity. Cellulose nitrate membranes are supplied as circles, sheets or rolls.