Derivatisation of amino acids for analysis

There are two main objectives under this heading (i) to convert amino acids into volatile derivatives for GLC and mass-spectrometric study and (ii) to introduce a group or groups with conveniently measured ultraviolet/visible absorption or fluorescence characteristics, so that TLC, HPLC, circular dichroism and other physicochemical and spectroscopic studies, or analytical separation of amino acid mixtures, may be accomplished. The analytical methods themselves are discussed in Chapter 3 and in later sections of this chapter. 

1 Preparation of S-acylamino acid esters and similar derivatives for analysis 

Unfortunately, the OPA condensation products decompose to some extent on the HPLC column (as shown by means of 14C-labelled amino acids - the positions of emerging samples shown by their fluorescence lag behind maximum radioactivity profiles), although users favouring these OPA derivatives have learned to practise strict protocols for their use, in order to get reliable results. The OPA-TV-acetyl-L-cysteine condensation product is a diastereoisomer mixture when formed with a 

Thin-layer chromatography (TLC) provides convenient routine analytical support of synthesis and other amino-acid interests and has been used in the Mosher procedure just described. It is most generally used for free amino acids and peptides, with spray reagents based on ninhydrin, or on the above derivatives ( post-TLC derivatisation ). Dansyl and phenylthiohydantoin (PTH) derivatives have been used for many years for identifying amino acids in mixtures by TLC ( pre-TLC 

General sources of information on amino acids are listed at the end of the Foreword. 

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