Quantitative determination of amino acids in potatoes

Quantitative analysis or “fingerprinting” of amino acids in feed stuff is required for evaluating quality, stability, and occasionally the provenience of the product. This concerns free as well as protein bound amino acids, after hydrolysis.
The method described is the determination of free amino acids in potatoes; it can be readily adapted for other tasks.
Determination of free amino acids in potatoes is required, e.g. when by-products of potato processing plants are to be used for animal feed, for which the content of free amino acids is regulated. Nowadays, pure amino acids are obtained from potato juice.
Potato juice is deproteinated by precipitation with ethanol. The free amino acids are derivatized with dansyl chloride, chromatographed on silica gel and scanned by fluorescence. The limits of determination are in the low nanogram range