# Comparing Methods of Determination of Dissolved Oxygen Content in Water Sample

I am currently doing an IB Chemistry Individual Investigation on dissolved oxygen in water samples by using Winkler method. However, my teacher suggested that I have to use oxygen probe as a standard and comparing the efficiency of dissolved oxygen content determination between Winkler method and other methods.

My problem is I don't know what method I have to compare with the Winkler method that I had done. Are there any suggestions or improvements on my investigation to let it have more exploration aspect?

### Let's abstract your task to determine dissolved oxygen (DO) to something more general:

1. You have to tie an observable to a concentration.
2. It would be nice if the method would work over a broad range of concentrations.
3. The method should be specific, or, alt least, very selective.
4. If possible, this relation should be linear.
5. It would be nice if the method could be packed into a sensor that works on its own (permanently or in cycles) and does not require a lot of personal interaction (= autonomous probe)

### What properties of molecular oxygen dissolved in water can be measured?

• In water, $\ce{O2}$ can be reduced electrochemically: $\ce{O2 + 4e- + 2 H2O -> 4 OH-}$
→ Have a look for galvanic and polarographic oxygen sensors
• Molecular oxygen is known to quench the luminescence of electronically excited states of dyes. The observed luminescence intensity (and lifetime) is reciprocally proportional to the the concentration of the quencher(Stern-Volmer equation)
→ Have a look for luminescence-based oxygen sensors