General Filtration Methods for Analytical Sample Preparation

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Sample Prep Tip: Losing Small Samples?
Working with small sample volumes (<1 mL) and experiencing significant volume loss to your sample prep filters? 

Using an appropriate filter designed for these small volumes will minimize holdup volume and improve your sample recovery. Our 4 mm diameter Millex® syringe filters and Ultrafree®-MC centrifugal filters will efficiently process small volume samples with holdup volumes as low as 5 µL.

Need Help Selecting the Right Microfiltration Membrane for your Application?

Merck Membranes, Filters and Devices: Keeping it Clean Since 1954.

Membrane filters and devices from Merck have been used by life sciences researchers, medical schools, hospitals, dialysis centers and many industries to separate molecular components of fluid samples for decades.

For a detailed introduction into our membrane technology, access our membrane resource center and the link below. Or, click through the subsections above for an overview and introduction to Merck membranes.

Prefiltration Media

Use prefiltration to remove larger particles (>10 micron diameter) from your fluid, so that you can perform subsequent, finer filtration step without clogging that downstream filter. Prefilters can be made of fibrous media or membrane filters and have a larger pore size than the final filter.

Merck offers a variety of prefiltration media to suit your application needs.

Microfiltration (Micron Filtration)

Microfiltration is the process of removing particles or biological entities in the 0.025 micron to 10 micron range from fluids by passage through a microporous medium such as a membrane filter. Although micron-sized particles can be removed by use of non-membrane or depth filters such as those made of fibrous media, only a membrane filter having a precisely defined pore size can ensure quantitative retention. Membrane filters can be used for final filtration or prefiltration, while depth filters are generally used for clarification, where quantitative retention is not required, or as prefilters to prolong the life of a downstream membrane.

With a broad selection of polymers over a wide range of pore sizes, there is an Merck membrane that meet your application needs.

Types of filtration by particle size.

What type of filter(s) do you need? Here’s a filtration chart to get you started. MF=microfiltration (micron filtration); UF=ultrafiltration; RO/NF=reverse osmosis/nanofiltration; P/F=prefiltration.