GC/MS and ESI/MS identification of the new generation plasticizers - cis and trans isomers of some 1,2-cyclohexane dicarboxylic acid di(n- and isononyl) esters

1,2-Cyclohexane dicarboxylic acid diisononyl ester is also known as diisononyl cyclohexane-1,2-dicarboxylate (DINCH) is a complex mixture of the hydrogenation products of diisononyl benzene-1,2-dicarboxylate (DINP). They are the new generation plasticizers used instead of the dialkyl benzene-1,2-dicarboxylate in order to improve the flexibility of polymers (mainly PVC) and strongly reduce the toxic effects on human health during their release from polymers to the environment. The identification of these compounds was done by syntheses of some DINCH constituents, i.e. cis and trans isomers of three di(n- and isononyl) cyclohexane-1,2-dicarboxylates, such as di(3,5,5-trimethylhexyl) cyclohexane-1,2-dicarboxylates, di(2-methyloctyl) cyclohexane-1,2-dicarboxylates and dinonyl cyclohexane-1,2-dicarboxylates by catalytic hydrogenation of appropriate DINP and their analyses by gas chromatography - mass spectrometry (GC/MS) and electrospray - mass spectrometry (ESI/MS) methods. Both GC data (values of the retention times tR and arithmetic retention indices IA) and mass spectra obtained for these isomers allowed to determine their chemical structures. ESI/MS mode of analysis of these compounds gives the knowledge about their mass fragmentation without the differentiation between individual cis and trans isomers.