Particles in liquid samples need to be removed prior to analysis. This is to avoid any damage to equipment such as ICP and ion chromatographs. This is what sterile syringe filters are for.
Compared to the complex setup of Buckner filters, they are inexpensive and use less. In addition, the syringe filter can filter the gas and bacteria in the sample. However, you ** note that syringe filters are disposable or reusable.
How do I choose a needle filter?
There are two aspects to consider when selecting a syringe filter. Let's look at some of the most important:
1. The aperture
Filters have different apertures. Common ones are 0.2um and 0.45um. Most programs typically use a 0.45um filter. However, if there are very fine particles in the sample, it is advisable to use particles of 0.2 or even 0.1um. It is important to note that there are other ways to filter very small particles, such as centrifugal filters, which may be a better choice.
2. Filter material
Needle filters are also available in a variety of filter materials. Cellulose acetate, polyethersulfone and polyamide are just some of the common ones. In addition, they have certain compatibility, so be sure to choose carefully. The material will also affect the EFA or effective filtration area and will also affect the capacity.
3. Filter size
As particles accumulate over time, they can clog pores and eventually disable filters. That's why it's important to choose a syringe filter that can hold more fluid. In general, larger diameter filters have higher retention volumes. Retention is the amount of liquid left after using the filter. It is also recommended that smaller diameter filters be used with rare and expensive fluids.
Use of syringe filters
Here are some suggestions on how to use syringe filters. Although we list these methods below, it is best to go through the full trial process.
When you are not concerned about low concentration contamination and are handling high concentration samples:
1. Obtain ** suitable filters.
2. Inhale 1ml of air and take a sample in a sterile syringe.
3. Pour 1 ml of the sample into the waste liquid container.
4. Drain remaining samples into clean vials for storage.
5. Push the first inhaled air into the same vial. This step will push out the remaining liquid and reduce the retained volume.
6. Dispose syringes and filters properly.
When you are concerned about contamination, the process is very similar, but there are other steps that need to be performed before taking a sample:
1. Use the most appropriate filter.
2. Soak up 1ml of air cushion, then soak up 10ml of blank matrix (e.g. mili-Q or 1% nitric acid)
3. Eject the substrate and air cushion into the waste container.