Samples come into the lab from all over the North East and Midwest US. Carrots, spinach, and soil… So what happens once they arrive? Let’s go through a day in the life of the lab —
As soon as samples arrive (ideally on the same day though certainly always), we input the survey data and log the sample in. We have a big database and system for collecting and managing the data (which is a lot) so all future data input can be connected to one single sample ID.
Also, the samples will rot quickly before they are run through the extraction process (basically mush sample, freeze, mix with methanol). Once extracted, they are centrifuged (to separate the extract, the methanol that has water soluble nutrients and stuff in it) and the ‘slug’ (the solid carrot that remains) and put in the freezer where they are safe for weeks without any problems.
On the soil side of things, we air dry the sample, then some of it is measured for biological activity. This process involves getting the sample slightly wet, to initiate some microbial activity. This activity produces CO2, which builds up in the container. We use a big syringe for the container because we can push out a little bit of air in a controlled way to measure the CO2. The CO2 rises over 24 hours and poof! we have a rough estimate of biological activity. The tool we use to do this we also built our self (commercial equivalent is $6/test… ours is… $0/test)… 🙂
Another bit of the soil sample goes into the oven at 650C. Sample weight is measured on the way into the oven and again on the way out to see how much carbon burned off in the process, giving us Total Organic Carbon.
Once we get enough samples (usually 48), we run polyphenols, antioxidants, and proteins on the carrot/spinach extract in the freezer. All these methods are basic chemistry – mix some stuff with the sample, wait a while, and see if the color changes due to some reaction. Measure the color change and poof! you have a value. We use the reflectometer we built for this application, rather than an off the shelf one. We use the same device to measure the reflectance of the carrot when it comes in, and the reflectance of the supernatant. We hope that these spectral signatures will correlate to lab measured soil or nutritional values, but we don’t have enough data to make that determination at this point. We also use the Our Sci platform to calculate the standards and error check to reduce mistakes.
So while running around measuring samples, we’re also building Bionutrient Meters for testing and eventually for the community and the Soil and Nutrition Conference in December.. We 3d print all the cases at this point, but it means we have to keep the printer running 24/7 to make a few hundred devices. So let’s get that going.
Ok, back to our samples – now we prepare both soil and food samples for the XRF – a pretty magical tool. It shoots X-rays at the sample which excite the atoms on the samples surface. When an electron on an excited atom ‘calms down’ (ie drop down a shell or two), exactly one photon is produced. By counting the photons and measuring their energy, you can pretty accurately figure out what types of atoms are present – in other words, what elements and how much. This is great, because the other way to get minerals data is more expensive and time consuming. The XRF requires that samples are similar size and shape, so making a gritty powder of all of them seems to work pretty well.
Also, thanks to Rhizoterra for training us on the instrument!
Of course, no lab is complete with dishes… lots and lots of dishes. Some look similar to our dishes at home, some not so much.