Week Four: First Setback

Happy Friday and welcome back to my blog!

I can’t believe the first month of my Senior Project/internship has gone by! It’s crazy how fast time flies. This week I mainly focused on my internship.

I continued to conduct PFAS Acid MIP Fabrication and Sensing experiments, but this time I did it with a different type of PFAS – PFBS (PFAS with four carbon-fluorine chains) and PFOS in water (or PFOS Water MIP). That just means the PFOS stock solution is water-based instead of acetone or methanol-based; the PFOS I used last week was dissolved in acetone, and the PFBS I prepared this week is dissolved in methanol. I made a 500 ppb (parts-per-billion) stock solution of PFBS and then later diluted that concentration of PFBS in water to 1000 ppt (parts-per-trillion) for sensing/detection.

Because both steps take hours, in addition to the electrode having to soak in a solution overnight or over weekend, the whole experiment is a two-day process. My original agenda was to complete the PFBS MIP Fabrication on Monday, Sense on Tuesday, complete PFOS Water MIP Fabrication on Wednesday, and Sense on Thursday. However, as I was in the middle of sensing on Tuesday, my MIP “burned”; essentially, the way the system measures voltage stopped working resulting in significant current going through the MIP, ruining it. Thus, the past day-and-a-half’s worth of work was all in vain. It was not a fun experience to say the least, but apparently, it’s a “milestone” that everyone runs into in the lab at least once.

Well, it was not entirely all in vain because I used the Sensing data I collected before my MIP burned to create a graph. The connection (white wire circled in the picture below) on the reference electrode broke, so the reference electrode became disconnected, and the computer could no longer recognize it. The reference electrode is the long, glass structure with a wire of silver inside behind the gold electrode, and it serves as the reference voltage for the experiment. There is an extremely thin and delicate wire inside the harness, and the continual usage sometimes causes them to break.

Usually, when characterizing I get the beautiful duck curves seen during CV as well as the DPV and OCP graphs, but the malfunction caused me to only see a single dot, and the resulting graph was just blank. Since the system can’t measure voltage, it overcompensates which usually damages the electrode. After my coworker helped me replace the wires, I was able to obtain measurements of the current again.

Electrode in the PFBS Solution (Fiona Xu)

Determined to make up for the time already lost, I quickly (but efficiently) redid the PFBS MIP Fabrication during the remainder of the day. I was proud of myself for finishing the Fabrication in record time; before, I would stop between each step to triple-check I was doing each task correctly, but now I’m becoming more confident in the procedure. Then, I sensed on Wednesday, and Thursday I completed the PFOS Water MIP Fabrication. When I return from the weekend I will sense with it. Even though everything in my agenda was pushed back one day, I’m glad I didn’t let the setback faze me.

I also presented my own experimental data in our weekly meetings for the first time: I presented my PFOS Acid MIP and Sensing Run data from last week on Monday and the PFBS Acid MIP and Sensing data on Friday. After I finish my data analysis in RStudio, I compile the graphs and statistics into a PowerPoint to show my results. My results agreed with previous experiments from the lab! There is a steady drop in current during the experiment which sometimes makes it difficult to determine if PFAS is detected. There is still a lot to investigate regarding the reasoning behind such behaviors (i.e. why does the current drop X amount from this step to the next?).

That concludes my work for this month and I’m looking forward to April!

Fiona