top of page

Bulk Media Formats And Terminologies

This blog is part of our separation science primer series which provides an easy-to-understand overview of key topics in solid-phase extraction (SPE) and chromatography.


This blog focuses on bulk media formats and terminologies used by us while describing our products, and processes. Similar formats and terminologies may be used by other scientists and vendors.


Formats and Terminologies

Bulk media are also called the stationary phase material or resins. It is packed into different separation (SPE and chromatography columns) devices, packed with the media available in various formats.

We offer our media in two formats:

  1. Loose Spherical Microbead Powder. This is the widely used format. Loose flowing spherical microbeads are filled into the separation devices. Spherical microbeads are emphasized here because loose, irregularly shaped powders are available and used for certain applications (e.g., SPE). Spherical microbeads are more preferable due to their performance benefits.

Depending on the application, these microbeads are of different sizes (diameters) and filled into the devices in different ways (loosely or tightly). For example, read our blog on SPE formats and terminologies to learn how the different ways in which they are packed into SPE devices.

2. Monoliths. Our manufacturing process allows the same crosslinker that binds the starting

materials into spherical microbeads to further chain each microbead into a continuous three- dimensional network. This continuous three-dimensional network form a single porous structure. This structure is in the form of a disc or cylinder and is called a monolith.


Within each format, depending on the chemical composition or physical properties of the media, additional terminologies could be used to further describe it. These include:

  1. Normal phase or hydrophilic interaction media. The material is hydrophilic or water-attracting in nature.

  2. Reverse phase or hydrophobic interaction media. The material here is hydrophobic or water-repelling in nature.

  3. Ion exchange media. The material here has a charge on its surface. If it has a negative charge, it is called a cation exchanger, positively charged an anion exchanger, and both positive and negative charge a zwitterionic exchanger.

  4. Affinity media. In this format, the spherical microbeads have a ligand on their surface that binds (has affinity) to a specific antigen or molecule.

  5. Multimodal media. These materials are also called mixed-mode media. The material chemistry allows multiple chromatography interactions (e.g., hydrophobic and ion exchange or hydrophobic and affinity).

  6. Electrically conductive media. The material is used in electrochemically modulated liquid chromatography (EMLC). Under an applied voltage, its surface allows manipulation of interfacial properties (e.g., surface charge and oxidation state) to attract or repel permanent or transient charges of the compound.


Other terminologies could be used depending on the separation device and technique:

  1. SPE Media. This media is packed in SPE columns, cartridges, and pipette tips.

  2. QuERChER media. The media is loosely contained (dispersed) within a device (e.g., centrifuge tube). QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) dispersive SPE is a well-known sample preparation approach in pesticide residue analysis.

  3. Flash media. This media is packed in SPE columns, cartridges and pipette tips.

  4. Analytical media. This media is used for analytical LC. They are also sometimes referred to as high-performance LC media or HPLC media.

  5. Preparative media.  This media is packed in preparative columns.

We offer a suite of bulk media products employing our award-winning NanoPak-C carbon microbeads for sample cleanup and preparation for LC analysis. These include:

  1. NanoPak-C All Carbon Microbeads Reverse Phase Media.

  2. NanoPak-C Functionalized Carbon Microbeads Multimodal Media.

  3. NanoPak-E Electrically Conductive (EMLC) media.


Custom products across these formats are also available.


Visit our store at www.millennialscientific.com/shop to learn more.


bottom of page