728Compounds containing amino groups are among the most important classes of organic compounds and are widespread in nature [1,2]. These compounds are widely used in chemical technology, science, and industry for the synthesis of drugs, dyes, and antioxi dants. 4 Chloro 5,7 dinitrobenzofurazan is used as an efficient reagent for determining aromatic amines and hydrazines in air, water, and biological fluids by spec trophotometric, test, and chromatographic methods [3,4]. Therefore, it is of interest to identify factors influ encing the selectivity of the separation of 5,7 dinitroben zofurazan derivatives of aromatic amines by reversed phase high performance liquid chromatography (RP HPLC).The mobile phase in liquid chromatography fulfills a double function. From one hand, it serves to trans port analyte molecules along the chromatographic column; therefore, the physical properties of the sol vent, such as viscosity, volatility, etc., are important. From the other hand, the mobile phase plays an active chemical role: it interacts with the molecules of the retained substances and also with the molecules of the stationary phase, influencing the results of separation [5,6].The objective of this work was to study the nature and composition of the mobile phase effect on the selectivity of separation of 5,7 dinitrobenzofurazan derivatives of amino compounds.
EXPERIMENTALIn this work, an HPLC system HP 1100 (Hewlett Packard) was used; it consisted of a four channel gra dient pump HPG1311A with a degasser HPG1322A, a Reodyne injector 5525 HPG1328A, a column ther mostat G1316A, a diode array detector HPG1315A, and a ChemStation data processing system with the G2170AA software. Separation was carried out on a Zorbax SB C 18 column (250 × 4.6 mm) protected with a Hypersil guard column ODS (50 × 4 mm). The injection volume was 20 μL. The quantitative process ing of the chromatographic data for different versions of detection was performed by chromatographic peak areas. The optimization of the separation conditions was done by 3D chromatogram images on the coordi nates time-signal intensity-wavelength.Acetonitrile and methanol of chromatographic purity (Criochrom, St. Petersburg) were used. Water of chromatographic purity was obtained using a Simplic ity 185 system.The selectivity coefficient was calculated using the equationwhere t R, 1 and t R, 2 are retention times of two compo nents, t 0 is column dead time, and t 0 = 2.48 min (determined using uracil).
RESULTS AND DISCUSSIONIn chromatography, the molecules of compounds to be separated and the solvents compete for the active binding sites on the adsorbent surface [7⎯9]. In many cases, molecules of the mobile phase are adsorbed on the stationary phase surface, changing the properties of the adsorbent. Therefore, it is possible to influence the mechanism of substance retention by varying the nature and composition of the mobile phase. Often a Abstract-Selectivity coefficients of a series of 5,7 dinitrobenzofurazan derivatives of amino compounds in the separation by reversed ...
