Aldehydes, detection thin layer chromatography

Many impurities are present in commercial caprolactam which pass into the liquid wastes from PCA manufacture from which caprolactam monomer may be recovered. Also, the products of die thermal degradation of PCA, dyes, lubricants, and other PCA fillers may be contained in the regenerated CL. Identification of die contaminants by IR spectroscopy has led to the detection of lower carboxylic acids, secondary amines, ketones, and esters. Aldehydes and hydroperoxides have been identified by polarography and thin-layer chromatography. 

Diphenylacetyl-l,3-indandione-l-hydrazone, first prepared by Braun and Mosher [143], reacts readily with carbonyl compounds such as aldehydes and ketones in weakly acidic media. The derivatives are separated by paper or thin-layer chromatography [144]. The derivatives are excited at 400-415 nm and emit at ca. 525 nm. The limit of detection is 2 ng per spot. 

The amino group is readily diazotized in aqueous solution, and this reaction forms a basis for the assay of sulfas. Aldehydes also react to form anils, and the yellow product formed with 4-(dimethylamino)benzaldehyde can be used for detection in thin-layer and paper chromatography. Chromatographic retention values have been determined in a number of thin layer systems, and have been used as an expression of the lipophilic character of sulfonamides (23). These values have corresponded well with Hansch lipophilic parameters determined in an isobutji alcohol—water system. 

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