ИСТИНА

Schiff bases (imines) can be obtained by condensation of aldehydes or ketones with amines. They have been known for more than 130 years, but they became the subject of many investigations relatively recently. Last years there is a pronounced tendency of growing attention to the problems of synthesis and practical application of Schiff bases. The interest to these compounds in analytical chemistry is connected with the fact that their protonated form in aqueous solution is colored. This provides for possibility of using such type of reactions for photometric determination of aldehydes, ketones and amines. In spite of a lot of works devoted to the analytical application of the reactions of Schiff base formation, search for new forms of ketonic- and amino-components is still of current importance. This is connected with the fact that aromatic amines used in such a reaction are frequently carcinogenic. Besides, the crucial question is improvement of sensitivity of analysis due to the determination directly in the sorbent or chemosorbent. We have found that terminal toluidine groups of polyurethane foam (PUF) can participate in condensation reaction with different aromatic amines resulting in formation of colored polymeric Schiff bases. The spectra of these products were recorded using diffuse reflectance spectrometer. The influence of phase contact time, acidity, temperature and concentration of carbonyl component on the yield of the polymeric Schiff bases has been investigated. It has been shown that Kubelka-Munk function of the polymeric Schiff base depends linearly on the concentration of aromatic aldehyde in the solution. This proves a fundamental possibility to determine the carbonyl components by the condensation with PUF. The determination of major moiety in food vanillin has been made. The main advantages of PUF as a polymeric chromogenic reagent are: relatively low cost, availability, mechanical durability, chemical stability in diluted acids and solvents. It can be easily separated from other components of the reaction mixture. This approach is promising for monitoring aromatic aldehydes in environment.