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Bromophenolblue and similar indicatorsA carefully dried TLC plate is sprayed with a 0.05% solution of indicator in ethanol (bromophenol blue, bromothymol blue, bromocresol green et.c.)Acidic compounds appear as yellow spots against a blue or green background and basic compounds as blue or yellow spots against a yellow background. Some pH adjustment may be necessary to get the desired background (acidic or alkaline) in particular if an acidic or basic eluent has been used. |