Selective determination of secondary amino acids as their N-dimethylthiophosphoryl methyl ester derivatives by gas chromatography with flame photometric detection

Abstract

A selective and sensitive method for the determination of secondary amino acids by gas chromatography (GC) was developed. After removal of primary amino acids by reaction with o-phthalidialdehyde and subsequent extraction with diethyl ether, secondary amino acids were converted into their N-dimethylthiophosphoryl methyl ester derivatives and determined by GC with flame photometric detection using a DB-5 capillary column. The derivatives were volatile enough and stable, giving single and symmetrical peaks. The detection limits for proline, pipecolic acid, thioproline, hydroxyproline and hydroxypipecolic acid were 0.1–0.7 pmol injected. By using this method, low-nanomole amounts of secondary amino acids could be accurately and precisely determined without any influence from primary amino acids and other amines.