Amino Acids, Peptides and Proteins - Dévényi T., Gergely J. 1976

Gas chromatographic analysis of amino acid derivatives. State of the art. Capabilities and limitations of the method.
Introduction

(R. Kaiser and A. Proks, FRG)

Recently, gas Chromatography (GC) has become one of the most effective Methods of chromatographic analysis in organic chemistry, especially for studying volatile substances.

GC is a fairly simple method; the required equipment, which is relatively inexpensive compared to that of other instrumental methods, is highly reliable in operation. Only a few milligrams of a substance are sufficient for analysis. The analytical results are automatically recorded in a form convenient for quantitative evaluation, and with the appropriate equipment, quantitative determination can be fully automated. Usually, this requires knowing the qualitative COMPOSITION OF THE sample. However, it is also possible to analyze mixtures of unknown composition. GC analysis can be successfully used in place of other Analytical Methods for structural elucidation when choosing between several possible structures of an unknown substance. GC is characterized by exceptionally high resolution; there is practically no pair of substances that cannot be separated by GC, even though this is sometimes impossible with other methods. However, the main advantage of GC lies in the speed of the analysis. Within a few minutes or even seconds, the analytical result can be obtained either as a Column of figures or as a qualitative or semi-quantitative chromatogram. This is the most obvious advantage of GC over other methods. As mentioned above, GC is the most effective analytical method for volatile substances.

Amino Acids are non-volatile, so at first glance, it seems they cannot be determined by GC. However, considering that for purely structural analyses and chemical separations of mixtures, numerous derivatives of the starting material are prepared—which are colored and have varying solubilities—one can reasonably expect to find a way to prepare volatile and thermally stable derivatives for GC from the initially non-volatile and easily degradable substances. Thus, A wide variety of compounds, which would otherwise be analyzed only by less elegant methods, can be made accessible to GC analysis.

GC is a rapid analytical method suitable for studying all substances that can be vaporized, i.e., those that are volatile or can be converted into derivatives with such properties. For these substances, GC can provide both Qualitative and quantitative data. Amino acids can be converted into volatile derivatives, and therefore, they can be analyzed by GC, leveraging all the advantages of this method.

GC is primarily used for the analysis of mixtures. For pure substances, GC can determine their degree of purity by measuring the amount (and type) of impurities, as well as establish the chemical, physicochemical, and Physical Properties of the substances, even when they are mixed with other components. However, for Amino acid analysis, this latter application of GC is of little interest.