The following properties should be considered when selecting an appropriate filter for filtering two-stage biorelevant dissolution samples manually:
i.    Pore Size: In general, 0.45 μm pore size filters are suitable for testing most immediate-release drug products, including micronized drugs, in biorelevant media. This filter size effectively removes undissolved drug particles, except in the case of nanosized drugs.
ii.    Prefilter: A built-in prefilter is beneficial for high-dose drugs and drugs containing insoluble excipients. It facilitates the filtration process and reduces the risk of filter bursting.
iii.    Material: Opt for a filter with low adsorption tendencies. However, this choice can be drug dependent. Materials like PE, PES, and Nylon filters often exhibit higher drug adsorption compared to glass microfiber filters, hydrophilic PTFE, and PVDF filters.
iv.    Ease of Filtration: GMF is a hydrophilic filter that is ideal for manual sampling from multiple vessels because they can filter all type of biorelevant media easily.
v.    Filter Diameter: For optimal precision and accuracy, single use at each time point, 13 mm filter diameter filters are preferable compared to the 25 mm size, as they are adequate for rapidly filtering smaller volumes and lower the amount of drug adsorbed whilst instantly stopping the dissolution process.
vi.    Pre-saturation: The smaller diameter size allows for easy pre-saturation with a smaller volume (e.g. generally about less than 3 mL) of biorelevant dissolution sample.
vii.    Supply: It's important to note that while polypropylene as a filter material performs well, recent supply chain issues may impact its long-term availability.

Recommendation
For manual sampling, a 13 mm glass microfiber filter with prefilter is recommended but housed in a 25 mm casing for ease of handling. These filters do not leach into biorelevant media and consistently perform well in drug filter adsorption studies because of their reduced surface area. We sell these 13mm diameter filters in packs for 70.