A Novel Analytical Method for Trace Ammonium in Freshwater and Seawater Using 4-Methoxyphthalaldehyde as Fluorescent Reagent

Figure 5

Fluorescence emission spectra of six different solutions. (a) Ultrapure water; (b) + Na₂SO₃ + NaOH solution + sodium citrate; (c) MOPA solution; (d) (0.200 μmol/L) + MOPA + Na₂SO₃ solution; (e) (0.200 μmol/L) + MOPA + Na₂SO₃ + NaOH (pH = 11.4); (f) (0.200 μmol/L) + MOPA + Na₂SO₃ + NaOH + sodium citrate (pH = 11.4).