Colorimetric determination of micro quantities of vanillin.

A colorimetric method is described for the \nquantitative determination of microgramme \nquantities of vanillin based on its reaction \nwith excess of thiobarbituric acid in aqueous \nmedium containing specified amounts of \nhydrochloric acid or phosphoric acid. The \ncoloured complex shows a single absorption \nmaximum at 432-434 mμ and the colour \nintensity of the complex obeys Beer's law at \nthis wavelength when prescribed amounts of \nvanillin are reacted with thiobarbituric acid. \nThe interference of sugars in the reaction and \nthe application of the method to processed \nfoodstuffs containing vanillin have been discussed.