The fragmentation of eight volatile derivatives of alanine, valine, leucine, proline, and glutamic acid upon electron impact is studied for the concurrent ultramicrodetermination or the selective identification of amino acids by mass fragmentography. The relationship between the sensitivity of mass fragmentography and Zlo% values (percentage of the total ionization over m/e 10) of N-trifluoroacetyl-L-prolyl, N-benzoyl, and N-pentafluorobenzoyl derivatives of alanine, valine. leucine, and proline is also investigated. The results obtained in this study suggest that N-trifluoroacetyl-L-prolyl n-butyl ester, N-benzoyl n-butyl ester, N-pentafluorobenzoyl n-butyl ester, and N-trifluoroacetyl L-menthyl ester derivatives can be used for the concurrent ultramicrodetermination or selective identification of amino acids by mass fragmentogmphy because these four derivatives produce common intense fragment ions at m/e 166, 105, 195, and 83 or diagnostic ions, respectively. Although N-trifluoroacetyl-L-4-thiazolidinecarbonyl n-butyl ester, N-trifluoroacetyl n-butyl ester, N-trimethylsilyl n-butyl ester, N-trimethylsilyl I-menthyl ester. and trimethylsilylated derivatives do not produce the common intense fragment ions, these derivatives are useful for the selective identification of ultra amounts of amino acids using mass fragmentography monitored the diagnostic ions, respectively. The general common rules between sensitivity and I,,% values were not adhered among the derivatives studied. 340