Juliet Chen's blog

On Monday, we finally spiked our new phytoplankton cultures for the isotope uptake experiment. Coulter counter, fluorometer and PAM fluorometer measurements were taken before inoculation and at the conclusion of each time trial. It was great learning how to use all of these different instruments. The first day of the time series, we noticed the settings of the PAM were different from when we ran the original experiments. Having started the uptake experiment already, we decided to leave the settings until after this experiment was over to keep consistent data.

This week, I ran the solar simulator for the photodegradation experiment for the first time. All of my preparations from the past 5 week lead up to when I turned the instrument on Wednesday. It was much warmed than I expected, the temperature of my sample initially increased in temperature, but soon stabilized during the trial with the MillQ. Samples were taken at 2 hour intervals after the first hour, and due to the apparent stabilization in temperature, an overnight, 15 hour trial was conducted the next day, to test the long term effects of photodegradation on metformin.

This week, further preliminary experiments for the solar simulator have been conducted. Originally, the intention was to use an open circulating water bath to keep the temperature constant. However, after a few leaks and spills, a closed water bath will be used, with copper tubing to transmit the difference in temperature. So far, the temperature of the bath seems to be fairly constant but the bath has not been run for long enough periods of time to be able to conclusively identify the effectiveness of this technique.

During this week, I gained a better understanding of the use of the HPLC machine. Earlier in the week, I assisted in making different pH buffers for one of the solvents for the HPLC machine. Another person working on the metformin project showed me how the HPLC machine worked, and how to understand the date the machine generates. This has helped me greatly in understanding how the results of my photodegradation experiments will be generated, as well as showing me how to troubleshoot anything that may go wrong in the HPLC machine.

Due to the 4^th of July, this week was slightly shorter. The phytoplankton seem to be growing quite well, appearing to have been entering the exponential growth stage during the early to mid portion of the week. However, this growth could have been affected by the three days of break over the weekend during which the culture was not swirled. This hypothesis will have to be confirmed by further monitoring this week. The flasks they are growing in appear quite green now and I am excited to see how they will do during the next week.

This week continued to be more research on my project and application or practical skills.  I began to refine my experimental plan for studying the photodegredation of metformin, but experimentation will wait until the methodology for analyzing the concentration with HPLC has been refined further. Right now, I am beginning a related side project that will study the effect of different chemicals (including metformin and guanylurea) on the growth of C.vulgaris, a type of phytoplankton.

This week, I began my internship at OHSU in the Institute of Environmental Health. The project I will be working on is Distribution and Fate of Emerging Contaminants in Oregon Rivers. More specifically, I will be trying to understanding the fate of metformin, a type II diabetes drug and its breakdown product guanylurea in the environment. Despite metformin being the most commonly prescribed drug for this disease, it is surprising that there is very little about its environmental impact.