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SEPARATION AND IDENTIFICATION OF SOME NITROXIDIC DERIVATIVES OF NICOTINIC ACID AND ISO -NICOTINIC ACID BY HPTLC COUPLED WITH ELECTRONIC PARAMAGNETIC RESONANCE (EPR)

ABSTRACT High performance thin layer chromatography (HPTLC) can be coupled with spectrometric methods in order to improve the selectivity and sensitivity of component identification. The coupling of HPTLC with EPR involves removing each spot together with the stationary phase from the plate, deposition on the quartz capillary, and analysis. This method is used to separate and identify some nitroxidic derivatives of nicotinic acid and iso-nicotinic acid. The advantage of this method is elimination of the transfer procedure of the substance from the spot, due to the fact that the EPR spectra are recorded directly from the adsorbed-labeled molecules on silica gel. Moreover, this coupling represents a non-destructive method.