Week 2: Furthering pHstat data

Now that I was once again reacquainted with the pHstat, I continued on with testing for the optimum alkaline reagent concentration for the system. The system was perturbed within an abiotic environment using sodium hydroxide and hydrochloric acid. Originally I used sodium bicarbonate as the alkaline reagent during testing, however after many different concentrations ranging from 0.05M to 1.1M it was discovered that sodium bicarbonate had a pH threshold. Once the pH of the system was perturbed in an acidic direction the 1.1M sodium bicarbonate was unable to bring the pH of the system above a threshold of 8.09 pH, which was not useful for biological experimentation in the future. So instead I switched the alkaline reagent to sodium carbonate, which also interacted better with the carbonate chemistry of the media. From here I once again tried multiple concentrations and discovered that 0.1M sodium carbonate was the optimum concentration of alkaline reagent for the pHstat.

Once the concentration was discovered using the pHstat pH set point program, the concentration was also tested for the pH gradient program. At first it appeared all right over the shorter periods of time, depending upon the frequency, however there were many factors to consider when testing this system. This program was new for me since it was not included with the pHstat last year. Within the program there are settings of frequency, phase, amplitude and offset for the guide pH sine wave to follow. The system would try to follow as closely to the guide pH sine wave as possible. The system itself was created to mimic the pH changes the estuary goes through daily. Nevertheless, during experimentation it was discovered that the system was unable to keep up after an extended period of time and multiple sine waves were completed. This needed to be fixed before we could continue using the system. So Rachel worked on the system for the last part of the week while I did some maintenance around the lab and transferred the cultures that needed refreshing.