Friday, August 12, 2011
Winkler Method vs YSI meter
Week 4 Blog
My agenda for this week was focused solely on my research pertaining to Smugglers Slough. One of my main concerns was that I was getting out of the ordinary results or findings when comparing the two testing methods (YSI vs. Winkler Method). When expressing my concerns to Dr. Apple he advised me to set up an experiment to compare the two methods using 100 percent saturated water to see if they come up with the same dissolved oxygen reading. After completing the experiment I found that there was no significant difference between the two testing methods.
Upon finding that there were no flaws in my testing methods, Dr. Apple suggested that I standardize the sodium thiosulfate I’ve been using to get as approximate N-value (Normality). After completing the standardization of the sodium thiosulfate I discovered that I had been working with the wrong N-value this whole time. This was a big relief to me as now I knew why my results have been so out of the ordinary.
This week I learned that there are a lot of factors you need to take into consideration when using the Winkler Method. One being that you should insure that the reagents that you’re using are not too old. I discovered that during my study old reagents are capable of affecting your results during the titration process. Another thing that I discovered was that when calculating the milliliters of titration (ml of titration) that was used to get the milligrams per liter (mg/L D.O.) dissolved oxygen, you need to insure that you’re using the proper N-value. I discovered that if you use the wrong N-value your results will be inaccurate. Now that I have obtained this information, I now feel a lot more comfortable and confident about utilizing the Winkler Method.