by Stacy Carolin
As you can see, this whole process takes a lot, a LOT of time and effort, and it's easy to get overwhelmed and claustrophobic (well, at least to me). As one who blatantly chooses to not comply with any expendable schedules and rules, I've doctored this up by choosing to morph my own schedule so that each workday still comprises everything that I love to do. As I've said before, science is not 100% of my life (an essential point, as I believe diversity in many fields is what ultimately leads to inspired ideas and creations), so I don't let it consume 100% of my day.
I thought this time I'd share how I (somewhat oddly) have chosen to set up my life in LA. So here we go, last day of chemistry before we transition into the mass spectrometer instrument room. (Note: this is usually completed over two days, but we are in crunch mode because I fly back to Atlanta in less than a week... so don't get scared about the intensity, it's not
too normal)
7:30am: Ok, so what we left in the lab yesterday was our "dried-down" solid samples. Today we are going to use iron as our helper element to grab up all the uranium and thorium atoms for us so that we can dump everything remaining away. First I add 1.5 mL of hydrochloric acid to the Teflon beakers to turn the sample back into liquid acidic form, then transfer it into a centrifuge tube (a centrifuge is that machine that spins around really fast and makes any solids in the tubes collect together at the bottom). Next I add a drop of iron chloride, which makes the acidic solution turn yellow, then add drops of ammonia solution slowly. Ammonia solution is basic (opposite of acidic) so when it is added to hydrochloric acid it reacts to neutralize the acid, then once the solution has turned from acidic to slightly basic, it reacts with iron chloride to produce iron hydroxide (a reddish solid).
Iron hydroxide is the compound that happens to grab onto uranium and thorium!
So now, to get rid of everything else, I stick it into the centrifuge so that all the iron (and its grab-on buddies uranium and thorium) gets solidified at the bottom. Then I dump out all the remaining liquid ("supernate") from the tube. Next, to transfer our solid iron sample out of the centrifuge tube, I dissolve it in a little nitric acid and pour it back into its Teflon beaker.
10:20am: Time for dance! Jump on my bike and ride 15 miles from Pasadena to EDGE Performing Arts Center in Hollywood (fun!!)
11:30am: Class with Malaya at EDGE, absolutely amazing, I am so fortunate!!!
1:00pm: Ride back to Caltech from Hollywood (Fun note: After a recent serious bike accident related to too much exercise strain on my body, I now only ride back if I feel up to it and the weather isn't over 100 degrees; there is also a subway system that takes the same amount of time that I can use.)
2:30pm: Suit up and back into the lab! I put all the samples back on the hot plate to dry down into solid again, then add 1 mL of nitric acid to re-dissolve. While the samples are drying, I start preparing my "columns" to perform the final "column chromatography." Hmm, let's see if I'm able to explain how this works... Right now we have nice individual liquid samples each filled with iron, uranium, and thorium molecules all in little bonds together. Column chromatography is the method I use to get rid of that iron, then separate the uranium and thorium into two separate Teflon beakers so that they can be measured on the mass spectrometer separately. A "column" looks like a 5-inch tiny plastic straw with a wider diameter 1/2-inch long top section, which is what we load our liquid samples into. Inside the length of the thin part of the column is column resin, little solid beads that look like sand, which the sample's iron, uranium, and thorium grab onto.
After our sample is poured into the column and being held onto by the resin, I add different "eluents" (liquid solutions) one at a time to detach each molecule type
separately. This is pretty cool!-- as a particular eluent travels down the column straw, it can either pass by the molecules holding onto the solid resin, or it can replace the molecules, aka kicking them off and grabbing onto the solid resin in their place. So, first, I add nitric acid which replaces all the iron bonds and makes the iron molecules drip out of the column straw and into a waste beaker underneath. Next, I add hydrochloric acid, which detaches the thorium, which then falls into a clean Teflon beaker below. Finally, I add water, which releases the uranium atoms into a second Teflon beaker below. And we are now done with column chromatography (about 8 hours later, haha, dripping is slow!) Congrats! ;)
To finish, I add a drop of perchloric acid one last time to each of the uranium and thorium Teflon beakers and dry down on the hot plate again (which should remove any remaining organics), then repeat with a drop of nitric acid. We now have a batch of Teflon beakers filled with a tiny thorium solid and a batch of Teflon beakers filled with a tiny uranium solid. YES! We're ready! Time to move into the instrument room with the incredibly complex and expensive inductively-coupled plasma mass spectrometer. Boom!
12:00am: And time to ride home :)
Fun night-bike-ride through Pasadena.
Great day!
12:00am: And time to ride home :)