USC Dana and David Dornsife College of Letters, Arts & Sciences

Today our professor, Lisa Collins, visited and we worked mostly on setting up the lab work for the colorimetric analysis of ammonia. We had 26 test tubes prepared, 2 for each of our 13 samples (10 soil samples plus 3 duplicates). Miller and I labeled each test tube in a systematic way (1-1, 1-2, 2-1, 2-2), I did all the 1s, while he did all the 2s. Then I used the pipette to retrieve 3.0 mL of the soil sample from the erlenmeyer flasks that we had created earlier on July 18, and inserted into the test tubes.

Sabrina prepared another tray of 24 test tubes with the stock and blank solution. For each of these 50 test tubes, we added 400μL of salicylate catalyst. We created another mixed reagent that was 1 part chlorox and 9 parts alkaline-citrate reagent, which was equivalent to 3mL of Chlorox and 27mL of alkaline-citrate reagent. This would just be enough for the 50 test tubes that each needed 600 μL of the mixed reagent.

We actually didn’t have chlorox, so Dan and Miller had to drive to Two Harbors to get it. Then we added the mixed reagent to the test tubes. However, on the first two samples, we realized something went really wrong. Immediately after adding the alkaline-citrate, the sample precipitated, which was not supposed to happen. With the samples solidifying we are unable to run the samples through spectrometer and get an accurate reading. We had to quickly resort to a new protocol. The revised plan was to add 120mL of phenol, 120mL of sodium nitroprusside, and 300mL of chlorox solution to each of the 50 samples. The team was in full gears as we all took on individual tasks: preparing the reagents, pipetting solutions, sealing the samples with parafilm, and turning the test tubes upside down. Lisa even gave us a hand. Even with all this help we were barely able to make it to lunch.

During lunch we met up with Professor Jim Haw, who is the head of the Environmental Studies department. He was also my professor in quite a few classes. We told him how we sighted a rattlesnake up on our trail, and he became quite interested on hiking it. Unfortunately, he had a meeting, so he couldn’t do it. After lunch, we debriefed with Lisa about the teams’ aims and goals for our internship. We have about 3 weeks left, and we needed to prioritize on our deliverables. Once we finished, we went back to lab. We hoped that by the time we came back from lunch, the samples would have reacted with the solutions and changed color. It did not. Without any reaction, we aren’t able to do any analysis on the experiment. So our nitrogen testing was not successful.

For more pictures, click here: Day 46 Soil Analysis