[Skip to Content](https://www.sigmaaldrich.com#main-content) [![MilliporeSigma](https://www.sigmaaldrich.com/static/logos/purple/millipore_sigma.svg)](https://www.sigmaaldrich.com/US/en) Products Cart0 USEN Products ProductsApplicationsServicesResourcesSupport [Login / Register](https://www.sigmaaldrich.com/oidc-sign-in) [Order Lookup](https://www.sigmaaldrich.com/US/en/order-lookup) [Quick Order](https://www.sigmaaldrich.com/US/en/quick-order) Cart0 [Home](https://www.sigmaaldrich.com/US/en)[Applications](https://www.sigmaaldrich.com/US/en/applications)[Analytical Chemistry](https://www.sigmaaldrich.com/US/en/applications/analytical-chemistry)[Sample Preparation Techniques](https://www.sigmaaldrich.com/US/en/applications/analytical-chemistry/sample-preparation)Sample Preparation by Filtration # Sample Preparation by Filtration ![Chart comparing types of filtration by particle size](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/applications/analytical-chemistry/filtration-process-chart-620x320.jpg "Chart comparing types of filtration by particle size") Filtration is a separation technique used to concentrate or purify substances based on their physical or chemical properties. It is a simple and routine method used in many laboratories to remove insoluble particles from solutions and to prepare samples for analysis. Filtration is used to reduce sample complexity, improve clarity of viscous samples, and reduce background signals resulting in increased signal-to-noise ratios in analytical tests. * * * ## Related Products Slide 1 of 6 1 of 2 [![Millex™ hydrophilic PTFE syringe filter pore size 0.45 μm, diam. 33 mm, non-sterile](https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/images/236/391/f7018bf2-2e12-46d4-9ed6-74584b12bc73/640/f7018bf2-2e12-46d4-9ed6-74584b12bc73.jpg) \ Millipore \ SLCR033 \ Millex™ hydrophilic PTFE syringe filter](https://www.sigmaaldrich.com/US/en/product/mm/slcr033) Quick View [![Millex™ MCE syringe filter pore size 0.22 μm, diam. 33 mm, sterile, hydrophilic](https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/images/200/141/baab16db-3de3-4acd-9e70-da9c26c9f1af/640/baab16db-3de3-4acd-9e70-da9c26c9f1af.jpg) \ Millipore \ SLGSR33SS \ Millex™ MCE syringe filter](https://www.sigmaaldrich.com/US/en/product/mm/slgsr33ss) Quick View [![Samplicity® G2 Filtration System, Bold Blue Vacuum filtration system for sample preparation for HPLC](https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/images/227/305/b8933fe8-894a-439f-bbbe-3cea4c80bea5/640/b8933fe8-894a-439f-bbbe-3cea4c80bea5.jpg) \ Millipore \ SAMP2SYSB \ Samplicity® G2 Filtration System, Bold Blue](https://www.sigmaaldrich.com/US/en/product/mm/samp2sysb) Quick View [![Millex™ filter for the Samplicity® G2 System Nylon, pore size 0.45 μm, diam. 33 mm, non-sterile, hydrophilic](https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/images/248/353/e55e4d31-6d14-4f4c-8cb1-4a9c80ad4f74/640/e55e4d31-6d14-4f4c-8cb1-4a9c80ad4f74.jpg) \ Millipore \ SAMP2HNNB \ Millex™ filter for the Samplicity® G2 System](https://www.sigmaaldrich.com/US/en/product/mm/samp2hnnb) Quick View [![Multiscreen® 96 well Plate, hydrophilic PVDF membrane pore size 1.2 μm, non-sterile](https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/images/367/307/02cc58df-1d6d-49cb-8749-d939f37d5454/640/02cc58df-1d6d-49cb-8749-d939f37d5454.jpg) \ Millipore \ MSBVN12 \ Multiscreen® 96 well Plate, hydrophilic PVDF membrane](https://www.sigmaaldrich.com/US/en/product/mm/msbvn12) Quick View [![Multiscreen® 96 well Plate, hydrophobic PVDF membrane pore size 0.45 μm](https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/images/165/862/de806767-c214-4fba-8348-94fcec8f1033/640/de806767-c214-4fba-8348-94fcec8f1033.jpg) \ Millipore \ M8IPS4510 \ Multiscreen® 96 well Plate, hydrophobic PVDF membrane](https://www.sigmaaldrich.com/US/en/product/mm/m8ips4510) Quick View * * * ## Featured Categories [![Millipore® glass filter holders](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/categories/laboratory-filtration/glass-vacuum-filter-holders-mcp.jpg "Glass vacuum filter holders ")](https://www.sigmaaldrich.com/US/en/applications/analytical-chemistry/mass-spectrometry) [Laboratory Filter Holders](https://www.sigmaaldrich.com/US/en/applications/analytical-chemistry/mass-spectrometry) Elevate filtration: glass, stainless steel, plastic filter holders for liquid, gas. Syringe, in-line, vacuum, pressure choices await. [Shop Products](https://www.sigmaaldrich.com/US/en/applications/analytical-chemistry/mass-spectrometry) [![An assortment of Millex® syringe filters in various colors and sizes, displayed against a white background. These filters represent a range of small-volume filtration options for laboratory use. The filters come in different colors such as blue, green, yellow, purple, and red, indicating different filter types or pore sizes. Each filter has a circular shape with a conical funnel-like structure on top for attaching to a syringe. The central part of the filters is white with labeling that includes the brand name “Millex®”. Some filters have a transparent top section while others are opaque. There is also one funnel accessory included in the image which is used to assist with pouring liquids into the filter. These filters set the standard in small-volume filtration (1-200 mL), and their unsurpassed consistency in sample preparation has led to the development of many methods specifying their use.](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/categories/analytical-sample-preparation/sterile-and-nonsterile-millex-syringe-filters.jpg "Sterile and Nonsterile Millex® Syringe Filters")](https://www.sigmaaldrich.com/US/en/products/filtration/laboratory-syringe-filters/millex-syringe-filters) [Millex® Syringe Filters](https://www.sigmaaldrich.com/US/en/products/filtration/laboratory-syringe-filters/millex-syringe-filters) Choose Millex® syringe filters: sterile, nonsterile formats. Wide membrane, housing options for HPLC, UHPLC, dissolution testing compatibility. [Shop Products](https://www.sigmaaldrich.com/US/en/products/filtration/laboratory-syringe-filters/millex-syringe-filters) [![The image show a woman in a white lab coat, working with laboratory flask containing a red liquid, which is connected to another piece of equipment with blue liquid at the bottom.](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/categories/sterile-lab-media-filtration-and-cultureware/m3304-190625-028-stericup-e-picture.jpg "Millipore® Sterile Filters")](https://www.sigmaaldrich.com/US/en/applications/environmental-testing-and-industrial-hygiene/soil-solid-waste-groundwater-testing) [Millipore® Sterile Filters](https://www.sigmaaldrich.com/US/en/applications/environmental-testing-and-industrial-hygiene/soil-solid-waste-groundwater-testing) Seamless Sterile Filtration: Choose us for reliable Stericap® & Steripak® devices, ensuring sterile, quality solutions from mL to 20 L. [Shop Products](https://www.sigmaaldrich.com/US/en/applications/environmental-testing-and-industrial-hygiene/soil-solid-waste-groundwater-testing) [![Whatman® filter papers for qualitative and quantitative analyses](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/categories/filtration/whatman-filter-papers.jpg "Whatman® filter papers for qualitative and quantitative analyses")](https://www.sigmaaldrich.com/US/en/products/filtration/filter-paper) [Filter Paper](https://www.sigmaaldrich.com/US/en/products/filtration/filter-paper) Used commonly in quantitative and qualitative analysis, filter papers must be closely matched to the application according to the physical characteristics of the filter paper. There are many sizes, materials, types, and grades of filter paper available for a variety of applications.  [Shop Products](https://www.sigmaaldrich.com/US/en/products/filtration/filter-paper) * * * Overview Related Articles & Protocols Support Depending on the filtration method applied, particles or molecules are separated based on properties such as size, shape or charge. The liquid that passes through the filter is called the ‘filtrate’ and the collected or retained material is the ‘retentate’ or ‘residue’. - [Reverse osmosis](https://www.sigmaaldrich.com/US/en/search/reverse-osmosis?focus=products&page=1&perpage=30&sort=relevance&term=reverse%20osmosis&type=product) (ionic separation) separates ions or molecules using a semipermeable membrane or barrier. Applied pressure overcomes osmotic pressure and forces solvent to move from a high solute concentration to a low solute concentration. Reverse osmosis rejects a high percentage of organic matter, other than particulates, and >99% of salts. The typical membrane rating is based on sodium chloride retention (<0.001 µm, <100 Daltons) - [Ultrafiltration](https://www.sigmaaldrich.com/US/en/search/ultrafiltration?focus=products&page=1&perpage=30&sort=relevance&term=ultrafiltration&type=product) (macromolecule separation) separates particles and dissolved molecules from fluids based on particle size. Ultrafiltration is used for concentration, fractionation, desalting, and buffer exchange. The typical rating is a nominal molecular weight limit (NMWL) between 1-1000 kDa. - [Microporous filtration](https://www.sigmaaldrich.com/US/en/search/microporous-filtration?focus=products&page=1&perpage=30&sort=relevance&term=microporous%20filtration&type=product) (microfiltration) is used for particle retention/exclusion and sterilization because it separates/removes particles and biological entities, such as bacteria and cells, based on particle size. Pore sizes are typically between 0.025-10 µm and are rated as nominal (~98% retention) or absolute (100% retention of the size equal to the pore size rating). - [Clarification filters](https://www.sigmaaldrich.com/US/en/search/clarification-filters?focus=products&page=1&perpage=30&sort=relevance&term=clarification%20filters&type=product) are used for pre-filtration and particle analysis because they retain/remove large particles, aggregates, and debris based on size. They may be used as a primary filtration step before microfiltration.  Clarification filters typically have pore size ratings >5 µm. retained. ## Common Filtration Applications - [General particulate removal](https://www.sigmaaldrich.com/US/en/search/general-particulate-removal?focus=products&page=1&perpage=30&sort=relevance&term=general%20particulate%20removal&type=product) - Sample preparation for analytical techniques such as HPLC, UHPLC, ion chromatography, gas chromatography, and dissolution testing - Sterilization of cell culture additives - Concentration of proteins, nucleic acids and polymers - Separation of biomolecules within a sample - Preparation of buffers - Water purification Filtration is an essential sample preparation step before sensitive chromatographic analysis, such as HPLC and LC-MS. Particulates in samples can interfere with liquid, gas and ion chromatography analyses by clogging columns or column heads, or by generating contaminant peaks (“ghost peaks”) on chromatograms. Proper filtration of samples, solvents and buffers generates higher quality, more consistent analytical results. It also increases instrument uptime and prolongs column life. ## Types of Filtration Processes & Procedures There are many filters with different filtration media composition, each designed for particular applications. Filter selection depends on several factors, including: - Size of the particles or molecules to be excluded or included - Chemical composition of the sample - Compatibility of the filtration media with sample or solution - Sample viscosity Filters can be made from different types of materials, such as paper, cloth, cotton-wool, asbestos, slag- or glass-wool, unglazed earthenware, sand, or other porous material. Membrane filters are usually made from synthetic polymers (e.g. hydrophilized PTFE, PVDF, nylon, PES). Different forces can be applied to drive the filtration process. Filtration can be driven by simple gravity using a filter and a funnel, manually as in syringe filtration, or by centrifugal force. In vacuum-driven filtration, a vacuum pump is used to rapidly draw the fluid through a filter. [![Document Search](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/ecommerce/document-search.png "Document Search")](https://www.sigmaaldrich.com/documents-search) [Looking for More Specific Information?](https://www.sigmaaldrich.com/documents-search) Visit our document search for data sheets, certificates and technical documentation. [Find Documents](https://www.sigmaaldrich.com/documents-search) ## Related Articles - [Syringe Filters for Chromatography](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/nonsterile-chromatography) Syringe filter selection guide for HPLC, UHPLC, and Ion Chromatography using pore size, filter diameter, chemical compatibility, analyte binding, and extractables. - [Nanoparticle Ultrafiltration](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/nanoparticle-ultrafiltration) Filtration methods and membrane filter selection in nanoparticle purification and production. - [Dissolution Testing Filtration](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/membranes-and-devices-for-dissolution-testing) Hydrophilic PTFE Millex® syringe filters ensure accurate dissolution testing and sample preparation for HPLC analysis. - [Virus Concentration by Ultrafiltration](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/viral-concentration-amicon-ultrafiltration) Ultrafiltration using Amicon® Ultra centrifugal devices for concentrating virus in preparation of high titer virus stocks and isolation of virus from samples. - [Factors Affecting Analyte Binding on Membrane Filters: A Guide for Filter Validation in Pharmaceutical Analytical QC](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/millex-filter-analyte-binding) Syringe membrane filter selection and validation methods to assess analyte loss due to membrane filter adsorption in pharmaceutical quality control (QC) testing. - [See All (23)](https://www.sigmaaldrich.com/US/en/search/facet-search?focus=sitecontent&term=facet-search) ## Related Protocols - [HPLC Analysis of Polyphenols in Nero d'Avola Red Wine on Discovery® HS C18 (UV 280 nm)](https://www.sigmaaldrich.com/US/en/technical-documents/protocol/analytical-chemistry/filtration/hplc-analysis-of-polyphenols-in-nero-d-avola-red-wine) HPLC Analysis of Polyphenols in Nero d'Avola Red Wine on Discovery® HS C18 (UV 280 nm) - [Millicup™-FLEX Disposable Vacuum Filtration Units and demo video](https://www.sigmaaldrich.com/US/en/technical-documents/protocol/analytical-chemistry/filtration/millicup--flex-disposable-vacuum-filtration-units-and-demo-video) Millicup™-FLEX disposable vacuum filter was designed to reduce contamination and save time. The solvent-resistant unit allows for filtration into storage bottles. - [Samplicity® G2 Filtration System](https://www.sigmaaldrich.com/US/en/technical-documents/protocol/analytical-chemistry/filtration/samplicity-in-hplc) Samplicity® G2 filtration system enhances HPLC workflow; watch video tutorials and application notes for effective sample preparation. - [Qualitative Thin Layer Chromatography Analysis Ginkgo](https://www.sigmaaldrich.com/US/en/technical-documents/protocol/analytical-chemistry/thin-layer-chromatography/qualitative-thin-layer-chromatography-analysis-ginkgo) Qualitative Thin Layer Chromatography Analysis of Flavonoids and Quantification of Terpene Lactones in Ginkgo Biloba Extracts and Tablets - [Determination of Caffeine in Coffee Using High Performance Thin Layer Chromatography](https://www.sigmaaldrich.com/US/en/technical-documents/protocol/analytical-chemistry/thin-layer-chromatography/quantification-of-caffeine) HPTLC was used to analyze caffeine in coffee. Filtration of coffee through a PTFE syringe filter was the only sample preparation. Quantitation was conducted with a TLC scanner. - [See All (10)](https://www.sigmaaldrich.com/US/en/search/facet-search?focus=sitecontent&term=facet-search) ### Find More Articles and Protocols Enter Keywords Search ## How Can We Help In case of any questions, please submit a [customer support request](https://www.sigmaaldrich.com/US/en/support/customer-support) or talk to our customer service team: Email [custserv@sial.com](mailto:custserv@sial.com) or call +1 (800) 244-1173 ## Additional Support - [Chromatogram Search](https://www.sigmaaldrich.com/chromatogram-search) Use the Chromatogram Search to identify unknown compounds in your sample. - [Calculators & Apps](https://www.sigmaaldrich.com/US/en/support/calculators-and-apps) Web Toolbox - science research tools and resources for analytical chemistry, life science, chemical synthesis and materials science. - [Customer Support Request](https://www.sigmaaldrich.com/US/en/support/customer-support) Customer support including help with orders, products, accounts, and website technical issues. - [FAQ](https://maestro.my.site.com/knowledgeportal/s/) Explore our Frequently Asked Questions for answers to commonly asked questions about our products and services. * * * __Featured Articles__ [Factors Affecting Analyte Binding on Membrane Filters: A Guide for Filter Validation in Pharmaceutical Analytical QC](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/millex-filter-analyte-binding) Syringe membrane filter selection and validation methods to assess analyte loss due to membrane filter adsorption in pharmaceutical quality control (QC) testing. [Syringe Filters for Chromatography](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/nonsterile-chromatography) Syringe filter selection guide for HPLC, UHPLC, and Ion Chromatography using pore size, filter diameter, chemical compatibility, analyte binding, and extractables. [Nanoparticle Ultrafiltration](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/nanoparticle-ultrafiltration) Filtration methods and membrane filter selection in nanoparticle purification and production. [Dissolution Testing Filtration](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/membranes-and-devices-for-dissolution-testing) Hydrophilic PTFE Millex® syringe filters ensure accurate dissolution testing and sample preparation for HPLC analysis. * * * __Related Services__ [Milli-Q® Services & Support](https://www.sigmaaldrich.com/US/en/services/product-services/milli-q-services-and-support) Expert support for lab water systems with digital services optimizing system performance, troubleshooting, validation, and qualification. Top __Sign In To Continue__ To continue reading please sign in or create an account. Sign In__Don't Have An Account?__Register An unknown error has occured.