Systematization of the Gas-Chromatographic Parameters of Trimethylsilyl Derivatives of Amino Acids

The gas-chromatographic retention indices (RIs) of trimethylsilyl (TMS) derivatives of the simplest amino acids on standard nonpolar polydimethylsiloxane stationary phases were systematized. This processing of data included combining them for derivatives of the same amino acids depending on the number of TMS groups (from one to four) and calculating average RI values together with their standard deviations based on data from various sources of information. This form of presenting the results made it possible to identify the best characterized derivatives and evaluate the reliability of the retention indices known for them. The simplest additive scheme for calculating retention indices based on even limited data for the most common amino acids was formed to estimate their unknown values, control previously determined values, and identify erroneous data. The increment Delta RI = RI(bis) - RI(mono) for the transformation -CO2Si(CH3)(3) + -NH2 -> -CO2Si(CH3)(3) + -NHSi(CH3)(3) was well reproducible (118 +/- 9). The other increments Delta RI = RI(tris) - RI(bis) were different for the transformations -NHSi(CH3)(3) + XH -> -N[Si(CH3)(3)](2) + XH (238 +/- 35) and -NHSi(CH3)(3) + XH -> -NHSi(CH3)3 + -XSi(CH3)(3) (111 +/- 16). A method for monitoring the correctness of the obtained values of Delta RI was proposed.