Abstract: Eutrophication represents a significant pollution challenge affecting numerous lakes worldwide, with total nitrogen concentration serving as a key parameter for evaluating eutrophication status. The current standard method for total nitrogen determination in water, as specified in the Chinese National Standard “Water Quality-Determination of Total Nitrogen-Alkaline Potassium Persulfate Digestion UV Spectrophotometric Method” (HJ 636-2012), involves digestion of nitrogen-containing organic compounds using alkaline potassium persulfate followed by Ultraviolet-visible (UV-vis) spectrophotometric analysis. However, this standard method requires specialized autoclave equipment operated by trained personnel, creating implementation barriers in undergraduate teaching laboratories. This study presents an alternative digestion approach using oil bath heating with reflux condensation, demonstrating that extended heating duration achieves comparable digestion efficiency to autoclave methods. This modified protocol provides a practical solution for incorporating total nitrogen analysis into instrumental analysis curricula, simultaneously reducing operational complexity and safety concerns while promoting environmental analysis education in undergraduate programs.

Key words: Total nitrogen measurement, instrumental analysis experiment, UV-Vis spectroscopy, Green improvement of experiments