Preserve water samples for dissolved oxygen analysis in the lab

Hi guys, it is me again for this week. We practiced taking water samples today and worked in the lab. Since I was in the lab with Arthur to learn how to preserve water samples for dissolved oxygen analysis by following the protocol, I can only talk about what we did in the lab. When we take our water sample to the lab, we followed the protocol in the kit to add 8 drops of different agents into the sample to preserve the oxygen for further analysis in the future. The purpose of adding different agents into the water is to allow us to measure the concentration of dissolved oxygen in the water at a certain location. Basically, we use titration to determine how much acid we used to dissolved the precipitation in the water sample, and then to analytically calculate how much dissolved oxygen was in the water. The color indicator for titration was starch that had a color of blue. One thing about the titration was it was really hard to control the volume of the titration acid. We should be really careful because if it had been over-titrated, the sample was useless and we should start over again. The protocol was very straight forward. However, working with samples in the lab need to be very careful and accurate since any small error will mess up the result.