A sensitive, simple, and accurate spectrophotometric method was developed for the quantitative determination of some primary aliphatic and aromatic amines, that is, ethylamine, 1,2-diaminopropane, aniline, p-aminophenol, and benzidine. The method is based on the interaction of these amines in aqueous medium with 7,7′,8,8′-tetracyanoquinodimethane (TCNQ) reagent in the presence of a buffer solution and surfactant (in the case of aromatic amines) to form charge-transfer complexes measurable at maximum wavelengths ranging between 323 and 511？nm. Beer’s law is obeyed over the concentration ranges of 0.025 and 3.0？μg/mL and the molar absorptivity is ranged between 8.977 × 103 and 5.8034 × 104 ？L·mol？1·cm？1 for these amines. The method was applied for the determination of benzidine in the river, sea, and tap waters. The TCNQ complexes with the previously mentioned amines were formed in the ratio of 1？:？1 amine : TCNQ, and their stability constants ranged between 8.78 × 104 and 1.844 × 105？L·mol？1. 1. Introduction A great number of aromatic amines are of considerable importance in industrial, toxicological, and pharmaceutical aspects [1]. Short-chain aliphatic amines are presented widely in the aquatic environment due to their widespread use in several industrial, chemical, and manufacturing applications [2, 3]. Also these amines are common components of biological systems as degradation products of organic materials such as amino acids and proteins. In addition to hygienic problems due to stinging smell, these compounds may be hazardous to human health as they are sensitizers and irritants to skin, eyes, mucus membranes, and respiratory tract. Also they can react with certain nitrogen-containing compounds to form nitrosamines, which are potentially carcinogenic substances [4]. The charge-transfer (CT) reactions had been widely studied spectrophotometrically in the determination of aliphatic and aromatic amines that are easy to be determined based on CT complex formation with some electron -acceptors such as chloranil [5–7], 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) [8], fluoranil [9], dinitrobenzene [10], 1-fluro-2,4-dinitrobenzene [11], and 1-chloro-2,4-dinitrobenzene [12]. Most of the previous methods suffer from the lack of sensitivity and selectivity and the estimation of these compounds is applied in organic medium. 7,7,8,8-Tetracyanoquinodimethane (TCNQ) is strong electron acceptor and applied in the determination of several electron donor drugs containing primary, secondary, or tertiary amino group and the review of the literature in the last
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