Separation and estimation of organic acids on paper chromatograms

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Abstract
Qualitative examination of a number of common aliphatic acids on a paper chromatogram using n-propanol: concentrated aqueous ammonia as solvent, has shown that many of them can be readily separated. In the present paper Rf values are given and the results are also expressed in terms of log10 [image] plotted against the number of C atoms in the molecule in order to throw light on relationships in the chromatographic behavior of the acids. A quantitative method is descr. for estimation of ammonium salts of the acids after they have been separated on a similar paper chromatogram. It is based on the effect of the ammonium salts on a thymol blue-glycine reagent which is insensitive to free ammonia. The change in color of thymol blue is inversely proportional to the concn. of the salt from about 80% to about 20% neutralization of the reagent. The accuracy of the method (single detns.) is about [plus or minus] 10% when 50 [mu]g. of organic acid is present.