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What you need in order to determine if a gravity separation will improve your process.
So, you see me dragging these cases through the airport and wonder to yourself “Just what does The Separation Guru bring with him to do testing at customer sites?” Well, lets find out…
First off, if you see a bead of sweat dripping from my brow, it is almost certainly a direct result of the shorter case. Weighing in at a hefty (yet still eligible for checking as luggage on an airline) 96 pounds, is my Fisher Scientific ST8 table top centrifuge. This unit is capable of variable speed operation up to 10,000 g with the HighConic III rotor and is timer operated with a very smooth acceleration and deceleration. You barely realize its even running. Due to weight concerns, I went with a standard ST8 unit, though refrigerated models are available.
There are several rotors available for the ST8 and they are surprisingly easy to switch out for different tasks. While different rotors have different maximum speeds, I have found that the ST8 is able to correctly determine the maximum allowable speed of a rotor without operator input. After hitting start, a few seconds later the unit will tell you if you have selected a speed that is too high for the rotor and will adjust your setpoint if necessary.
Speaking of rotors, lets take a look inside my accessory case to see what we have to work with in there.
Most notably upon examining the contents, your eyes will be drawn to the High Conic III rotor on the left. This rotor claims a maximum speed of 9500 RPM, but it should be noted that this speed is only when at low temperatures. If not used in a refrigerated unit, the maximum speed is 8700 RPM. This fixed angle unit, which reaches a maximum g-force of 10,000 g at 8700 RPM is great for testing materials that are expected to need a high degree of separation capacity in order to reach a satisfactory result. As the tubes are at an angle, mixing from settling during the stopping process is minimized, though not entirely eliminated. The fixed angle spins can work for both liquid / solid separations as well as liquid / liquid separations when high g-forces are required. 50mL tubes are used, though adapters to hold 15mL tubes are seen in the front, left of the case.
In addition to the fixed angle rotor, there is a swinging bucket rotor with dual 50mL carriers.
These buckets can also be changed out with large, single 100mL buckets (though I haven’t found good tubes for those yet). The swinging bucket rotor maxes out at 4500 RPM which clocks in at a bit over 3000 g. This rotor is great for testing materials with lower difficulties of separation or liquid / liquid splits to get a clean interface showing in the tubes.
Of course we round out the case with a pile of test tubes.
Running out of test tubes is a cardinal sin of onsite work, don’t let it happen! I should note that not all tubes are created equal, some of them (like the blue cap and orange cap ones) have better graduation marks on the sides of the tubes making it easier to determine the quantities of various phases within the samples. Especially when the marks go all the way to the tip.
So what happens when I get to the customer’s site?
Once at the customer’s site, we spin and analyze results, spin again sometimes. All in an effort to determine what type of gravity separation, if any, can improve the customer’s process. After the lab testing is done, a path forward can be recommended which may include pilot testing in some cases or be able to go straight to production, depending greatly on the process needs.
If you are in need of assistance in determining what type of separation process is best for your needs, please contact me directly to discuss. I can guide you through the process from starting in the lab to continuous production. – Ben Holcombe, Separation Guru LLC.
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