Help us with a laboratory protocol
Posted on 2011-05-04
We process geologic samples in a mass spectrometer. There is a flaw in the protocol. Help us figure out a better way. Here's what we do:
1. Put small amount (measured in micrograms) of a sample into silver capsule. The silver capsule is a cylinder with one open end. It is very small, 2mm in diameter. After the sample is put in the capsule, the capsule is pinched shut and the top folded over twice.
2. Put capsule in the assay tray. Record on paper the position of the capsule. E.g. Cell A1 has sample from Site X. There are not identifying marks on the capsule itself.
3. The tray is 8 x 12, so as many as 96 samples might go in. Repeat 1 and 2 as needed.
4. Take tray to mass spectrometer. Put about 10-15 samples in mass spectrometer, leave the rest of samples in tray until the 10-15 are run.
The problem happens between steps 3 and 4. A couple of times, the tray has been knocked, causing the capsules to fall out. When this happens the information about which capsule contained a sample from which site it lost. For example, we don't know which capsule was in A1.
One thought was to stamp the capsule with the cell #, e.g. A1, before loading the sample, but this would not work because it would not be possible to undo the folding of the capsule to see the stamp. This also assumes we could get really small stamps.