A Modified o-Phthalaldehyde Fluorometric Analytical Method for Ultratrace Ammonium in Natural Waters Using EDTA-NaOH as Buffer

Table 5

Analytical results of the proposed method and classical OPA method.

Seawater sample	The proposed method (mol/L)	The classical OPA method (mol/L)	Calculated -value	Critical -value ( = 0.05)
1	0.536 ± 0.008 ( = 4)	0.560 ± 0.018 ( = 4)	2.43	2.45
2	0.385 ± 0.006 ( = 3)	0.360 ± 0.035 ( = 3)	1.22	2.78