NMR tubes in soapy water
Not surprisingly, NMR tubes have to be cleaned like any other glassware. (Read a bit more about nuclear magnetic resonance spectroscopy here, in case you missed my earlier post.) Since I’m using humic substances (the matter that results from the breakdown of organics and is the main component of soil), you can imagine that my samples can be fairly dirty. In many ways, I’m creating expensive, quantitatively measured muddy water in a laboratory as part of my research. And so, before attempting to wash the tubes, soaking them in a soap solution is advisable. Here, I used a graduated cylinder.
Now, these tubes are quite fragile and thin, being 5mm in diameter. When placed in the filled graduated cylinder, they simply float. Even pushing them under the surface of the water isn’t sufficient to get them to sink – the small diameter allows the air to cling to the inside of the tube rather than travel up and vacate the space. In the same way, a liquid sample will not fall out of the tube when turned upside down, unless perturbed by shaking, for example. To get the tubes to sink, some liquid had to be pipetted (injected) into the individual tubes. Patches of air underwater, seen in the photo above, remained in the tubes and slowly escaped.
After the tubes have soaked, a neat little tool is used to run water up the tubes and wash away any remaining residue. Continue reading about the process here!