VMA in urine is detected and semiquantitated by thin layer chromatography on silica gel plates. An ethyl acetate extract of acidified urine is spotted and chromatographed, with toluene/acetic acid/ethyl acetate (50/50/5 by vol) as the solvent system. The VMA appears as a blue purple spot on spraying the chromatogram with diazotized p nitroaniline. VMA is completely resolved from urinary contaminants and metabolites, and is semiquantitated by visual comparison with simultaneously spotted external standards, a comparison greatly facilitated by the stability of the developed color. With appropriate use of internal standards, the spot can be densitometrically measured.
