STUDIES ON A NEW TYPE ACID DYE——XYLENE CYANOL FOR THE DETERMINATION OF AMINES

In order to increase the sensitivity of the acid dye determination method, we have tested 70 kinds of acid dyes which possess sulfonic acid or carboxylic acid radical. These dyes, including sulfonphthaleins, azo dyes, triarylmethanes, nitrophenylamines, etc., have not yet been reported in the literature for the determination of amines. It is observed that only the dyes which possess sulfonie acid radical are useful in this method. Among these dyes, 10 kinds were selected for further examination, the result shows that xytene cyanol (XC) is one of two best dyes. The limits of identification of this dye for bencthtropine 1, 1-diphenyl-2 (3-tropanyl) ethene and benactyzine (benzilic acid 2-diethylamino-ethyl ester) are 17 ng/ml and 36 ng/ml respectively, The extinction coefficients (E_1cm^1%) of these dye-amine complexes are 4.2～6.2 times as high as those of bromothymol blue (BTB), but for more hydrophilic amines, E_1cm^1% are lower than those obtained from ETB. Chloroform extract of the complex shows greenish blue color, λ max 628.5 nm. For the determination of amines, the suitable concentration of XC is 4×10^-3 M. The calibration curve is a straight line in the range of 0～10 μg/ml. With XC concentration of 4 x 10^-3 M, the mole ratio of dye-amine complex in the chloroform extract for benactyzine is XC: Benactyzine=2: 1, and with concentration of 4×10^-4 M=1: 1. But, in the case of benethtropine, the mole ratio with different dye concentration(4×10^-3 M～4×10^-4 M) remains 2.7: 1 (XC: amine). The coefficient of variance for the determination of 0.2 μg/ml benethtropine or benactyzine is within±5% and ±1～2% for 2.5 μg/ml and 5.0 μg/ml. This dye is a new type acid dye for the determination of amines, and the following portion is considered to be the fundamental structure: