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Colour reagents and thin-layer , chromatography

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  341-343

2026-11-01

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Colour reagents and thin-layer

chromatography

Many common colour-test reagents are used routinely as locating reagents in TLC (e.g. acidified iodoplatinate solution, Dragendorff’s reagent, Marquis reagent, Van Urk’s reagent) (see below). These reagents may be applied by spraying or dipping. In high-performance TLC (HPTLC) it is more common to use an automated dipping device for applying locating reagents. It is worth noting that the preparation of the spray or dip equivalent of a colour reagent may differ slightly from that of the colour reagent preparation itself because spray reagents may need to be of a somewhat different viscosity to enable application to TLC plates.

It is also the case that the reaction and result ant colour that marks the presence of a certain substance obtained from spraying a reagent on TLC plates may differ from that obtained from a direct colour test and, in some cases, will not yield any results. This is because of pH effects, that is, whether the TLC plate has been dipped in 0.1 M sodium hydroxide and the substance tested is acidic in character (i.e. the free acid of a salt post-extraction). However, this aspect of colour reagents and their use in TLC as sprays can often give clues as to the drug’s or substance’s chemistry.