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1 2012

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On simple experimental evidence confirmed by HPLC data of supramolecular aggregation and aggregate mobility with S(+)-naproxen in aqueous ethanol solution

Sajewicz M., Gontarska M., Kowalska T.

Acta Chromatographica

2012

Vol. 24, no. 1

131--141

In our earlier studies performed with the use of thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), polarimetry, and several other instrumental techniques, we have provided abundant experimental evidence for the oscillatory chiral conversion and the oscillatory condensation of the low-molecular-weight carboxylic acids from the groups of profen drugs, amino acids, and hydroxy acids. We have also proposed several kinetic-diffusive models aimed at elucidation of these striking phenomena, which in the diffusive term assumed contribution from the density inhomogeneity of the investigated liquid systems. Moreover, each model laid special emphasis on the importance of cyclic H-bonded carboxylic acid homodimers of the SS and RR type. In this paper, we introduce a simple experimental approach enabling convenient registration of the density inhomogeneity in the S(+)-naproxen solution prepared in 70% aqueous ethanol. To this effect, we use a zooming scanner that is able to scan this solution in a Petri dish placed in UV light (λ = 254 nm). Scanning in the selected time intervals allows tracing the dynamics of supramolecular aggregation of the investigated profen drugs. The mobility of these aggregates can probably result from the energy released in the process of chemical polycondensation. The obtained results seem to correlate well with those originating from HPLC, and the relevant conclusions are drawn. It seems possible that the zooming scanner can prove helpful in monitoring some other interesting chemical processes as well, thus contributing to the studies on the mechanism and kinetics of the nonlinear organic reactions.