Monitoring DBP precursors in water with scanning spectrophotometer

This study used a scanning UV-Vis spectrophotometer to monitor humic acids in water. The results showed that the area under the UV-Vis spectra of a water sample was a good surrogate to monitor the concentration of the aqueous humic acids. No apparent difference was found between the UV absorbance spectra of the three commercially available humic acids (Nitrohumic acids, Aldrich humic acids, and Nacalai Tesque humic acids) used in this study. The use of the scanning spectra partially compensates for the random error in UV ₂₅₄ due to the heterogeneous humic acid composition. The major interference for the proposed method came from formazine turbidity and nitrate nitrogen. Although filtration with a 0.45 μm filter can remove most of the interference from formazine, some interference is still present at wavelengths less than 250 nm. Also it was found that the presence of nitrate nitrogen greatly affected the spectra of the humic acids. In order to monitor the DBP precursor in water with minimized interference, it is recommended that the area under the UV-Vis spectra between 250 and 350 nm should be used as a surrogate for concentration of DBP precursors in water.