Improved Detection of Ochratoxin A on Thin Layer Plates

Abstract
The fluorescent spectra of ochratoxins A, B, and C, one of the hydrolysis products of ochratoxin A, i.e., 5-chloro-3,4-dihydro-8-hydroxy-3-methylisocoumarin-7-carboxylic acid, and their respective ammoniated derivatives have been studied. The excitation maxima of these compounds shifted to a longer wavelength after exposure to ammonia fumes, whereas the emission maxima shifted to a shorter wavelength. The fluorescence intensity of ammoniated ochratoxin A was found to be almost twice that of ochratoxin A. It is suggested that TLC plates be exposed to ammonia fumes prior to densitometric analysis to increase the sensitivity of the assay for ochratoxin A.

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