As precious as aquatic environments are, it is difficult to analyze them because of their complex composition. Here we show the introduction of a new ionophore for potentiometric nitrite detection that allows micromolar limit of detection and discriminates chloride and nitrate by three to four orders of magnitude. Then, to facilitate the potentiometric analysis of anions in seawater, we presented a new device that selectively removes halides (incl. chloride) and cations from a sample without modifying the concentration of the other tested anions. This setup was further studied with a finite-difference-based numerical model. Finally, this thesis presents two experiments designed for hands-on teaching of chemistry. The first one is a low-cost flame emission spectrometer for the qualitative and quantitative observation of the ion emission phenomenon, while the second experiment is a quick flocculation demonstration that can be used to easily to demonstrate wastewater treatment in classrooms.