氨基酸与四氰代苯醌二甲叉的荷移反应的研究

Study on the Charge-transfer Complex of Amino Acids with TCNQ by Spectrophotometry

本文用分光光度法研究了 6种氨基酸与四氰代苯醌二甲叉 (简称TCNQ)之间的荷移反应。测定了配合物的不稳定常数 ,讨论了配合物的组成。考察了形成配合物的影响因素 ,确立了最佳反应条件 ,并测定了味精中谷氨酸钠的含量 。

The charge-transfer (CT) reaction between 7,7,8,8-tetracyanoquinodimethane (TCNQ) with six amino acids, L-leucine, L-lysine, L-arginine, L-phenylalanine, L-glutamic acid, and L-cysteine was studied in detail by spectrophotometry. The charge-transfer complexes between TCNQ and amio acids have stable yellow colour. Therefore a new and single method for the determination of amino acids has been established. The optimization of the experimental condition is described. The determination was carried out in the solution of 20% (V%) acetone with pH 9.8 at 415 nm. Beer's law was obeyed in the range of 0.2 x 10 (3) - 1.5 x 10(-3), 0.2 x 10(-3) - 1.0 x 10(-3), 0.5 x 10(-3) - 2.5 x 10(-3), 0.5 x 10(-3) - 2.0 x 10(-3), 0.5 x 10(-3) - 2.5 x 10(-3) and 1.0 x 10(-3) - 3.0 x 10(-3) mol (.) L-1 for leucine, lysine, glutamic acid, phenylalanine, arginine, and cysteine respectively. The instability constants of complexes were determined. The compositions of all these CT complexes are found to be 1:1 by different methods. The relative SDs are less than 2% ( n = 8). The proposed method has been applied to the determination of monosodium glutamate with satisfactory results.