The Use of 7,7′,8,8′-Tetracyanoquinodimethane for the Spectrophotometric Determination of Some Primary Amines Application to Real Water Samples

Table 3

Optimum conditions for the determination of primary amines with TCNQ reagent.

Compound	𝜆max (nm)	Temp. (°C)	Development time (min)	Buffer amount (mL)	TCNQ 1×10^−3 M (mL)	Order of addition	Surfactant 0.1% (mL)	Final pH
Aniline	323	RT^a	Immediately	0.5	0.5	III^b	CPC, 0.5	6.02
p-Amino-phenol	511	40	5	1.0	0.5	III	CPC, 0.5	9.86
Benzidine	500	RT	Immediately	0.8	0.5	IV^c	CTAB, 1.0	10.65
Ethylamine	464	40	20	—	1.0	—	—	7.20
1,2-Diaminopropane	470	50	30	—	0.5	—	—	6.62

aRoom temperature = 25°C.
bAmine + (KH₂PO₄ + KOH) + TCNQ + CPC.
cTCNQ + (KH₂PO₄ + KOH) + CPC + amine.