Vials and Stirring
We recommend the following:
4 mL vials manufactured from polypropylene or glass with PTFE/silicone septa.
We recommend using the Omega 5SC-TT-K-30-36.
Yes, most reactions need to have some sort of stirring however some chemistries (such as ones that utilize enzymes) rely upon shaking as stir bars could mechanically destroy the catalysts.
If the reaction is homogeneous (only one phase) then typically 300-500 rpm stirring suffices.
If however, the reaction is biphasic (solid-liquid or liquid-liquid) then stirring becomes critical because reactivity is dependent upon the interface interactions. For instance, Prof. David MacMillan’s group at Princeton University has several chemistries that use inorganic bases in organic solvents - here very high stir rates are required (ie >700 rpm).
Maximum stirring is not always beneficial especially if you have small reaction volumes because your reaction could get dispersed across the vial and no longer have contact with the stir bar.
We use cross-shaped stir bars as they tend to be more stable at higher RPMs.
If not centered, stirring turns into tumble stirring (end-over-end) which might be sufficient for some cases but likely not for all.
If your reaction is homogeneous this likely won't matter much.
Light and Intensity
The total radiant flux of the different wavelength LEDs we measured on a sample of one of each is:
450nm – 3.4 W @ 100% intensity
420nm – 1.8 W @ 100% intensity
365nm – 1.5 W @ 100% intensity
In a recent study, we measured the light density as 19.63 mW/mm2 at the vial location.
We cannot go lower than the minimum fan speed, as this is the slowest the fan will go without completely turning it off. We do not run it completely off as this will cause the LED to run too hot. Running the LED too hot will either result in a hard failure or will degrade its lifetime, depending on the operating conditions. The only safe way to achieve a higher temperature in the vial is to run the unit in a warmer environment, with the upper limit of 40°C, while either setting the speed to 2800 to maximize the rise or utilizing the target temperature set-point, if there is the risk that 2800 would overshoot.