When the needle filter is used to process the chromatographic sample, other impurities should be prevented from being introduced during the filtration process. The presence of such impurities may be such that the outer shell material or filter will shed particulates and be carried into the filtrate. Therefore, the materials of the filter membrane and the outer shell structure are very important, and different types of membranes are suitable for samples of different natures.
1) Hydrophilic sample: A hydrophilic membrane is used, which has affinity for water and is suitable for filtering water as a matrix solution. Useful membranes are: mixed cellulose ester, polyethersulfone (PES) Nylon, and the like.
2) Strong corrosive organic solvent: Generally, a hydrophobic membrane such as a membrane made of PTFE or polypropylene (PP) is used.
3) Protein solution: Select a low protein adsorption filter, such as a PVDF filter.
4) Ion Chromatography: PES membranes are generally considered to be suitable for filtration of solutions with low inorganic ions.
When selecting a needle filter, in addition to considering the above factors, consider the volume of the sample. Usually, when the sample volume is less than 2ml, use a 4mm diameter microfilter; the sample volume is between 2-10ml, and a 13mm diameter filter is selected. When the sample amount is more than 10 ml, a 25 mm diameter needle filter is selected.
1. Do not use syringes smaller than 10 cc, as small volume columns may cause pressure to exceed the upper limit, resulting in damage to the filter or personal injury.
2. Only for laboratory use, single use, non-renewable.
3. The filtrate at the beginning of the section should be discarded. The volume is about the dead volume of the filter. For example, in 25 mm, the first 1 mL of the filtrate is discarded; or the filter is pre-cleaned with a solution of 1 to 2 mL.