Image: my dimensional analysis and concentration/volume calculations for our Naproxen/Ibuprofen experiment.
After realizing our drug concentration wasn’t high enough in our experiment last week, we planned to increase our concentration from 100 µg/mL to 500 µM and 1000 µM for both Naproxen and Ibuprofen. However, after performing the calculations, we realized that our concentration still was far below the standard oral dose of the two nonsteroidal anti-inflammatory drugs (NSAIDs). Consequently, we decided that we would use 10 µL of each drug instead of attempting to calculate the volume of drug needed to reach a concentration of 500 µM and 1000 µM.
Attached above is a picture of my lab notebook with my calculations. To the right of the list of treatments, I calculated the stock solution concentration for both drugs. Stock solutions are solutions of reagents at convenient concentrations from which you can make appropriate dilutions. For instance, if a procedure calls for a 1:100 dilution, you use 1 part of your stock in 99 parts diluent (water), for a final total of 100 parts in the dilution. We dissolved the Ib and Nx powders in water for the stock solution, since both are most soluble in water. To determine the solubility of a drug, you can visit the Sigma page and look under the “properties” header; for instance, this is the Sigma page for Nx https://www.sigmaaldrich.com/US/en/product/sigma/m1275). Below those calculations, I used the dilution equation (M1V1=M2V2) to calculate the volume of stock solution needed to achieve the 500 µM and 1000 µM concentrations. After we decided to switch to 10 µL instead of 500 µM and 1000 µM concentrations, I used the same dilution equation, just solving for M2 rather than V1.
Although performing such calculations allowed me to become more comfortable with stoichiometry and dimensional analysis, the true learning moment of the week came after I had finished performing all of the calculations and carrying out all of the wet lab treatments. When I arrived at the hematology analyzer in the Jackson building, I was met with a red error light. Although the machine is often malfunctioning, I’m typically able to resolve any errors it throws my way. This time, however, I was presented with a software error that neither myself, my advisor, nor the other scientists in the lab could resolve. After an hour of troubleshooting, we concluded that it wasn’t going to let us analyze our samples today. So, after days of planning and hours of carrying out the procedure, I had to throw out all of my samples. I reflected on all the work I’d done that day to prepare the samples, and while I expected to be frustrated or upset, I realized that next week is just another opportunity to retry, this time with more experience and more resiliency when things don’t go exactly as planned.
Comments