Week Three: Patience Please

Hi there, and welcome to week three!

Spring is officially here, and we got some really nice weather this past week. The cherry blossom trees outside of the MITRE buildings are in full bloom, and the flowers look beautiful. I love catching a glance at them every time I go through the walkways between each building. My family and I are planning to see more in DC soon.

I’m going to start off this post by discussing my independent research instead of ending with it. I outlined my final paper and most likely the content in my final presentation. I found some articles on sensor technology’s use to clean water, but I want to keep searching for more. Ideally, I’m hoping to find a case study involving sensor technology cleanup of a specific waterway. Lastly, I began sorting my information on the Potomac River into more specific, water quality-assessing categories like pH and temperature levels; the Potomac River is split into several sites.

Continuing this theme of unconventionality, this week was different from usual because most of my coworkers were taking their extensive LC-MS training. Thus, there were no meetings, and I spent most of my time in the lab running experiments. On Monday, I finished the sensing process with the electrode I prepped with Acid MIP Fabrication last Thursday. I recorded my procedure in my lab notebook for future reference. I repeated those steps by doing the Acid MIP Fabrication on Tuesday and sensing on Wednesday; this was the first time I conducted the experiment independently or without guidance from a coworker at each step, but I still asked questions when necessary.

Each experiment is two steps: Acid MIP Fabrication and Current Sensing. To recap, the first step is preparing the electrode surface on which the PFAS will absorb onto. It creates the mold that the PFAS molecules will interact with – this is done by imprinting or creating little holes in the polymer (o-PD) sitting on the surface. The acid used is hydrochloric acid (HCl), which helps create an ideal pH for sensing PFAS. This process takes about two and a half hours, and it involves micro pipetting PFAS into water and making solutions. I must be precise and careful with each step because I’m working with very small samples in units such as milligrams and microliters.

The second step is conducting the actual sensing of PFAS in the [deionized] water sample created, which is what I did on Monday. The sensing has a much more straightforward procedure than the Acid MIP Fabrication, but it takes about five hours. This is because when we measure the current of or conduct CV on the redox reaction on the surface of the electrode (characterization), we run three iterations, so the same thing is repeated multiple times. Additionally, each iteration scans for and creates three graphs: CV, Differential Pulse Voltammetry (DPV), and the Open Circuit Potential (OCP). Thus, a lot of the sensing is waiting for the graphs to generate.

A lot of time is also spent waiting for the electrode to soak in water vials and then water spiked with PFAS. The electrode is then characterized after 20-minute intervals, and the methodology we’re doing calls for the electrode to spend 60 minutes total in each soak solution. The three graphs I mentioned above are then consolidated into one aggregate (mean) current for each soak, which I will expand on soon. Since I’m still new to this experiment, both the Acid MIP Fabrication and Sensing took a bit longer than expected, so you can imagine why I was busy in the lab much of this week.

(All images: Fiona Xu)

Above are images from my experiments. The yellow-ish solution the electrode sits in while being characterized is ferrocene methanol in sodium chloride, which I prepare a new solution of each time I conduct the Current Sensing step. The purpose of the ferrocene methanol is to act as the mediator molecule that gives us a signal (the current measured) indicating the presence of PFAS, as a decrease in current indicates detection of some PFAS concentration.

After I collected all of my experiment data on the lab computers, I exported them into RStudio, the programming software we’re using to create graphs and do statistical calculations as I mentioned above. This is useful for when I’ll create presentations to report my data to everyone. Next week, I get to do this all over again.

Thanks for reading,

Fiona