An Amperometric Biosensor Based on Alanine Dehydrogenase for the Determination of Low Level of Ammonium Ion in Water

Table 3

The interference effect of Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe³⁺, SO₄²⁻, CH₃NH₂, and C₂H₅NH₂ at different molar ratio of interferent to 𝑁𝐻₄⁺ ion on the determination of 0.68 mg/L 𝑁𝐻₄⁺ ion using AlaDH electrode at pH 7 (𝑛=3).

Interferent	Current difference (×10^−7 A) at different molar ratios of interferent: NH4^+ ion
	0 : 1	10 : 1	100 : 1	1000 : 1	5000 : 1
Na^+	0.560±0.025	0.558±0.033	0.589±0.027	0.531±0.012	0.313±0.083^∗
K^+,	0.560±0.025	0.522±0.036	0.164±0.047^∗
Mg^2+	0.560±0.025	0.567±0.006	0.535±0.017	0.527±0.033	0.187±0.077^∗
Ca^2+	0.560±0.025	0.556±0.043	0.449±0.040^∗	0.291±0.066
Fe^3+	0.560±0.025	0.616±0.024	0.173±0.017^∗
SO4^2-	0.560±0.025	0.603±0.032	0.260±0.165^∗
CH3NH2	0.560±0.025	0.626±0.014^∗	0.893±0.037
C2H5NH2	0.560±0.025	0.760±0.009^∗	0.806±0.012

* 𝑡value>𝑡 critical value at 95% confident level with 4 degrees of freedom