Involving Fractionation of the Organic Acids

A general technique has been described by Nordmann et al. for the separation of nonvolatile organic acids of urine (N20, N21, N22) and blood (N19). It includes two-dimensional paper chromatography preceded by the elimination of the compounds which interfere with adequate resolution and separation of the spots. 

The first solvent used for chromatography is an alkaline one (containing ethanol, ammonia, and water), the second one an acidic one (consisting of n-propanol, formic acid, eucalyptol, and water). 

The procedure is applied at least on duplicate samples of the urine to be studied. 

When unusual spots are found on these two standard chromatograms, it is of course necessary to run more samples of the urine through the process to provide supplementary chromatograms for other location techniques (N2) or to make specific tests on the eluate of such unknown spots. 

In the case of blood plasma, the technique includes the same steps, preceded by the elimination of plasma proteins, which is done either by ultrafiltration or by the technique of Hunter (H32). Methods of depro-teinization using stable acids (like trichloroacetic acid) are not suitable, since the added acid would interfere with the subsequent chromatography. 

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