Particles from liquid samples need to be removed before they undergo analysis. This is to stay away from any damage to an equipment like ICP and ion chromatography. This is what a sterile syringe filter is for.

They are cheap and is used in small volumes compared to the complex set up of Buckner filters. Additionally, syringe filters can also filtrate gases and bacteria in a sample. However, you have to note that syringe filters are either disposable or reusable.

How to Choose Syringe Filters?

There are a couple of aspects to consider when you are choosing syringe filters. Let us look at the most important ones:

1.Pore Size

The filters are available in different pore sizes. The common ones are 0.2um and 0.45um. 0.45um filters are generally what is used in most procedures. But, if there are very minute particles in a sample, it is wise to use a 0.2um or even a 0.1um one. It is important to note that there are other ways to filtrate very small particles too such as centrifugal filters, which might be a better option.

2.Filter Material

Syringe filters also come in a wide range of materials used for the filters. Cellulose acetate, polyethersulfone, and polyamide are just some of the common ones. Moreover, they have specific compatibility so it is important that you choose carefully. The material will also affect the EFA or effective filtration area and will also affect the capacity.

3.Filter Size

When particles build up over time, they can block the pores and will eventually render the filter useless. This is why it is important to choose a syringe filter that can hold up higher volumes of liquid. Usually, a filter with a larger diameter has a higher hold-up volume. The hold-up volume is the amount of fluid that remains after the filter is used. It is also suggested that filters with smaller diameters should be used with rare fluids and those that are expensive.

Methods for Syringe Filter Usage

Below are suggested methods on how to use syringe filters. Although we listed these methods below, it is still best to go through with your thorough process of trials.

When you are not concerned with low-level contamination and is working on a sample with high concentration:

1.Get the most appropriate filter to use.

2.Draw 1ml of air followed by your sample in a sterile syringe.

3.Eject 1ml of the sample in a waste container.

4.Eject the rest of the sample in a clean vial for storage.

5.Push the air you initially drew into the same vial. This step will push out the remaining fluid and will reduce the held up volume.

6.Properly dispose of the syringe and filter altogether.

When you are concerned with contamination, the process is pretty similar but there are extra steps to take before drawing the sample:

1.Use the most appropriate filter.

2.Draw 1ml of air cushion followed by 10ml of the blank matrix such as milli-Q or 1% nitric

3.Eject the matrix along with the air cushion in a waste container.

Proceed with the steps mentioned above and do not forget to dispose the

sterile syringe filter along with the syringe vitself.