Monday, 4 August 2014

What happens to wool samples in the lab? Part 3

After washing and grinding, the sample needs to be got ready for the analysis itself. When being loaded into the mass spectrometer, the powder is contained in capsules made of pressed metal foil:
Unbelievably tiny capsules
These are both 3.5 mm across by 5 mm high. The one on the left is made of tin (for carbon and nitrogen isotope value analysis) and the one on the right is made of silver (for hydrogen and oxygen isotope value analysis). As you can imagine, loading sub-microgram amounts of highly static hair powder into these is a recipe for madness... especially if you've got to do scores of them in triplicate....

Microbalance plus tools
We weigh exactly how much sample is in each capsule. We do this on a very sensitive balance. The object to be weighed is placed on the small round platform you can see inside the perspex cylinder. This is then closed so that no air movements can disturb the weight. I am loading pinches of hair powder with the very fine tweezers you can see. I clean these between each sample using methanol, which is in the orange-labelled squeezy bottle.

Lab book with weights and trays with samples
Storage tray close-up
Once we've got the right amount of powder in the capsule, we fold it tightly to stop it falling out again. Then we put the folded capsule in a storage tray. These have 96 little wells, so one sample goes into each. The weight of the sample in each well is recorded. We can then take (or send) the samples to the lab where the actual analysis will be done.

Next: running the analysis. This next post will have to wait for a bit, as I won't be doing this for a few months...