chemistry journal of moldova

Gh. Zgherea/Chem.J. Mold. 2008, 3 (1),52-55The second program of binary mobile phase, BGMP II(40 minutes, figure 3), contains four time segments too;in figure 4 there are the chromatogram of synthetic mixture SM II, obtained with BGMP II. The synthetic mixture SM IIcontains the same 2.4DNPH-ones as SM I, in the ratio of volume:2.4-DNFHAA: 2.4-DNFHD: 2.4-DNFHA: 2.4-DNFHiBA = 4:1:5:5.As in previous case, the first timing segment, g=1 (t=15 min), the mixing program assures an eluent with 45%water, for the best separation between 2.4-DNPHAA and 2.4-DNPHD; the polarity of mobile phase is higher (themolecules of 2.4-DNPH-ones are strongly retained on the stationary phase).The second timing segment, g=2 (t=10min, n=9.9), the percent of water is reduced at 20%; this value is constantand during the third timing segment, g=3 (t=15min). Subside of mobile phase polarity produce a desorbtive processfrom the stationary phase. The timing segments, g=4-8 haven’t got a specific content. In the last timing segment, g=9(t=5min, n=0.1) quickly rebuilds the initial mixture of mobile phase; at the finish, the analytical system is completelyready to a new separation.Comparing the chromatograms from figures 2 and 4, may be concluded that the BGMP Iassure a better separationfor the 2.4-DNPHAA and 2.4-DNPHD; for the 2.4-DNPHA and 2.4-DNPHiBA, the resolution is comparable.The figure 5 is a chromatogram of a natural mixture of 2.4-DNPH-ones, for the inferior carbonyl compounds ofbeer. The liquid-chromatographic separation is on the same column and the eluting program GBMP I.Figure 4.The chromatogram of SM IIAA - chromatographic signal for the 2.4-DNPHAA;D - chromatographic signal for the 2.4-DNPHD;A - chromatographic signal for the 2.4-DNPHA(after the same retention time appear the signal forpropanal);iBA - chromatographic signal for the 2.4-DNPHiBA.Figure 5.The chromatogram ofnatural mixture of 2.4-DNFH-onesUsing the external standard method, for the chromatographic signal of 2.4-DNPHAA, obtain 14.75 mg· L -1 asconcentration of acetic aldehyde in beer; the value is in concordance with the literature. The surface of chromatographicsignal of 2.4-DNPHD offer a value of 2.5 mg·L -1 as concentration of diacetyl in beer; this value is higher. In beer, thenormal values of diacetyl concentration is 0.01-0.2 mg·L -1 ; 0.15 mg·L -1 is the threshold value.ConclusionsOn the basis of these experiments may be formulating the following conclusions:1.Was established two optimal programs for providing mixtures of binary eluent; according them, it is provided54