Prepping for the Plasma Machine (ICP)

Hours upon hours of ossicle sorting have almost paid off—we're finally going to analyze the samples using the ICP-MS.


I'll explain in a moment, but first: some ossicle samples from the brittle star O. californica were analyzed using hypo-spectronomy and found to transmit light between wavelengths of 530 and 590 nanometers—the spectrum of visible green light—which happens to be the color of brittle star bioluminescence. Therefore, it is very likely that the tiny bones in the arms of certain brittle stars are optimized to transmit and ideally amplify the light from their luminescent reactions. How amazing is that?! These are specialized bones in a specific luminescent system that aid in defense or mating or whatever else the brittle stars use luminesce for. Well, anyways, I was excited.

Okay. Back to the issue of ICP analysis.

ICP-MS stands for Inductively Coupled Plasma Mass Spectronomy. As another intern explained to me, it is the process of heating up argon gas into the fourth state of matter, that is, plasma. Once there is plasma in the chamber of the machine, samples (which need to be in liquid form) are sent into the chamber in a kind of mist after being nebulized. The drops vaporize near the plasma and solids break down into individual atoms after being vaporized and certain chemical elements are ionized. These ions are sorted in a special device for mass spectronomy, which can determine the presence of elements of atomic mass 7 to 250 and their proportions in the sample. In the case of the brittle star ossicles, we want to find out how much of what elements are in the bones of luminescent brittle star species compared to proportions of the same elements in non-luminescent species in order to determine if those elements (mainly metals) play any role in specialized light transmission and refraction.
During this and last week, I continued to sort more of the A. pujetana ossicles since I had less of that sample compared to my O. californica and A. squamata samples. I sorted as much as I could on Thursday and then weighed all the samples. All the weighing and digesting, etc. had to be done in order so that it would be easier to organize the samples once we got the results back from the ICP. The order I used was: Blank_1, Blank_2, Blank_3, OCL, OCT, OCV, ASL, AST, ASV, APL, APT, APV. The first two initials stand for the species name (i.e. O. californica) and the last letter stands for what kind of ossicle it is, that is, Lateral Shield, Top/Bottom Shield, or Vertebrae. 
After the ossicles were weighed, I added approximately 150 microliters of 70% Nitric Acid (or about two large drops from a disposable glass pipette) to each tube in order to dissolve the samples into a liquid. A glass pipette was used instead of the more accurate mechanical pipette because Nitric Acid is so strong it or its fumes could potentially harm the sensitive measuring device in a normal pipette and make it unusable or in need or serious repair. Once the acid was added, the ossicles sat for 12 or more hours to insure optimum digestion.

The container and tube were tared, then the sample was added. The weight (usually in milligrams) was recorded in a text file on the computer that the scale was hooked up to. [Note: in the picture it shows a tube with a cap on; in the actual weighing the cap was never put on in the scale due to the fact that if more grams are tared the less accurate the measurements of the samples will be.]

"JUSTRITE: Acids and Corrosives Storage Cabinet"

Not More than 70% Nitric Acid. It's extremely bad for your health (note the skull and crossbones), severely reactive, and extremely dangerous on contact, but worry not! it's not flammable. You need to wear goggles & shield, lab coat & apron, and proper gloves when using this acid under a vent hood.

The amazing vent hood, which, in the clean room, is always blowing on high, keeping this part of the lab at high negative pressure and sucking out any harmful or plain stinky acid or chemical smells.

 In the pictures below, acid is added to the sample of O. californica vertebral ossicles and bubbling occurs due to the reaction between the calcium carbonate in the tiny bones and the Nitric Acid, which facilitates the creation and release of Carbon dioxide gas.

The tubes, once the sample and acid are weighed, are put in a tube rack under the fume hood so that the acid can fully dissolve the ossicles into a fluid liquid to be diluted with MilliQ water after full digestion. The resultant liquid will be nebulized into the ICP-MS for analysis.

I recorded the weights on the computer and in my notebook. Notice how minuscule the sample sizes are in terms of weight (in grams).

I have yet to get the results from the ICP, but am nonetheless optimistic that they will be quite interesting and certainly worth a follow-up post!