Analytical reactions of 2,4-dinitrophenylhydrazine with some aldehydes in micelles of cationic surfactants

Abstract

The analytical effect of micelles of cationic surfactants in the reactions of some aromatic aldehydes (AA) with 2,4-dinitrophenylhydrazine (DNPH) with the formation of the corresponding aci-forms of hydrazones has been established. It has been established that micelles of nonionic and anionic surfactants do not cause analytically significant effects in the system under study. Analytical characteristics of systems DNPH–AA– cationic surfactant (molar absorption coefficients (ε), ranges of determined contents, limits of detection) were determined, using the example of benzaldehyde and its nitro-, sulfo-, chlorine-, dimethylamino- and methoxy derivatives, as well as p-dime thylaminocinnamic aldehyde (DMAC). For the majority of aldehydes ranges of determined contents are in the range from 0,2 to 2,1 μg/ml, ε from 2.10-4 to 1.10-5 L.mol-1.cm-1. The hydrazone formed by DNPH and DMAC was synthesized and identified by elemental analysis and IR spectroscopically. The solubility of the resulting hydrazone in aqueous (pH 13) and micellar (cetylpyridinium chloride, CPC) media was studied. It has been shown that its solubility in CPC micelles increases approximately 60 times, which leads to the stabilization of the studied system DNPH – AA – cationic surfactant in time (its isotropy) and an increase in the sensitivity of the determination of the corresponding aldehyde in the absence of volatile and toxic organic solvents, while the principle “green chemistry” has been implemented. The established effect of cationic surfactants was implemented to develop a method for the non-extraction photometric determination of streptomycin (a broad-spectrum aminoglycoside antibiotic effective against tuberculosis) in pharmaceutical preparations with ranges of determined contents from 2,1 to 87,4 μg/ml. The error of direct photometric determination of streptomycin did not exceed 5–9%.