Additionally, bonding reversed phase moiety to silica reduces its chromatographically available surface area and therefore limits loading capacity. This is a result of the bonding process which consumes and deactivates the active adsorption sites which interact with components to be separated. The bonded phase also blocks access to micropores where the majority of the silica surface area lies. The un-bonded silica typically used in normal phase flash chromatography possesses considerably more accessible surface area for adsorption than reversed-phase media.
I am personally not a fan of the way Ayende proposes it. This is an Ambient Context , which is a specific sort of service locator construct. Doing this hides the dependency, because classes can call that static class without you having to inject it. Explicitly injecting it makes it much clearer that you need to unit test time. Besides that, it makes it hard to write tests for frameworks such as MSTest who tend to run tests in parallel. Without any countermeasures, it makes your tests very unreliable. A better solution -for the example- is to have an IClock interface, as is suggested here . As you can see, that answer scores much higher than Ayende approach, that is shown in the same SO question.