Syringe filter is a filter connected to the front end of the syringe. In HPLC analysis, the particle size of the chromatographic column packing is small and it is easy to be blocked by impurity particles. Therefore, samples and solvents need to be filtered in advance to remove particulate contaminants and protect the instrument. Ion chromatography, which is commonly used in environmental analysis, also requires that no inorganic contaminants be introduced in sample pretreatment. Filtering sample solutions is an important step in the sample pretreatment process.
Preparation before use
1. After the syringe filter and the shell are thoroughly cleaned and sterilized, the filter should be installed. First, apply clean water or clean filtered liquid on the "O" ring of the syringe filter as a lubricant, and then carefully insert the syringe filter vertically into the socket plate at the bottom of the filter. If you are using the 226 interface, insert the interface ears into the chassis, and after the filter "O" ring enters the socket, screw it in clockwise to make the ears snap into the holes of the chassis. After installation, tighten the bolt seal.
2. After the filter is installed, the entire filter system must be thoroughly rinsed with clean water.
3. After the entire filter system is rinsed, it can be filtered.
4. Filtration and cleaning operations in the production process.
a. Filter operation
Open the exhaust valve and slowly open the feed valve to introduce the liquid to be filtered. When the liquid flows out from the exhaust valve port, immediately close the exhaust valve and slowly open the discharge valve.
In the initial stage of filtration, since the syringe filter is still very clean and the filtration speed is also very fast, the pressure in the filter is generally maintained at 0.05-1Mpa. As time goes by, in order to maintain a proper filtration rate, the internal pressure can be gradually increased. However, the maximum pressure in the filter cannot exceed the maximum operating pressure allowed by different material filter elements (please refer to the technical parameters of various filter elements).
When the pressure in the filter is already high and the filtering speed slows down more, the filtering operation should be stopped and the filter should be cleaned.
b. Backwash of filter
⑴ For the fine filtration of mineral water and water treatment, when backflushing, you can backflush with clean water first, and then backflush with clean water after terminal filtration, and then put it into production.
⑵ For the filtration of fermented liquids and sugar-containing liquids such as beer and beverages, it is recommended to backflush with clean and oil-free compressed air after pretreatment, then backflush with clean water, and then backflush with clean water after final filtration. After that, it can be put into production again.
⑶ When the syringe filter has been used for a long time, and the filtration speed is still not satisfactory after backflushing with the above method, the syringe filter can be removed and placed in a NaOH solution with a concentration of 2-4% for 4-8 hours, and rinse with clean water after terminal filtration until there is no residual lye, and then put it into the filter to continue using.
⑷ For manufacturers who do not produce continuous production in three shifts, it is recommended to rinse the filter clean before the end of each shift to prevent long-term adhesion of dirt and bacterial clusters, which will affect the normal operation of the next shift.
⑸ When the syringe filter has been used for a long time, although the filtering capacity of the syringe filter cannot be restored by the above-mentioned methods, it means that a new syringe filter should be replaced.