We have done contact angle measurements on the microbeads who are an indirect measure of hydrophobicity. As the contact angle increases, the surface of a material is considered to transition from hydrophilic to hydrophobic characteristics. Contact angles greater than 90 degrees are considered to be hydrophobic. The contact angle of NanoPak-C all carbon microbeads is between 90-100.° Studies (For e.g.’ see Polymers 13(19), 2021) show that the water contact angle for C18 is 105-110° and C8 is 90-95.° The contact angle of other graphitic substrates is between 85-95.°The contact angle and, thus, the hydrophobicity of our carbon microbeads is similar to other graphitic substrates and closer to C8. We can also tweak the composition to increase the water contact closer to C18.

All carbon microbeads do not exhibit the characteristic properties of activated carbon. Activated carbons are suitable adsorbents to irreversible retention and removal of nuisance compounds (e.g., color removal) via solid-liquid (adsorption) chromatography mechanism. Activated carbon has a high specific surface area (e.g., 900 m2/g for charcoal) and micropores (less than 20 A° in diameters). However, these micropores lead to poor mobile phase mass transfer. Also, their isotherms are strongly non-linear due to the wide range of surface reactivity. Thus, they are unsuitable for separating analytes by the liquid-liquid chromatography mechanism.