Esterification of amino acids with thionyl chloride acidified butanols for their gas chromatographic analysis

Racemization of aspartic acid in the extracellular matrix proteins of primary and secondary dentin

“…First, a 1.25 N solution (1 ml) of SOC12 in isopropanol [17] was added to the sample in a screwcapped vial, filled with nitrogen, and heated for 1 hour at 100°C. Excess reagents were then evaporated at room temperature in a vacuum.…”

Hydroxyproline interference during the gas chromatographic analysis of D/L aspartic acid in human dentine

“…Small variations in the conditions of derivatization (e.g. the acidity of the isopropanol) could explain the different yields of the two species, although these are kept as constant as possible; esterification time has been found to strongly influence the quantitative recovery of amino acid derivatives (Cruikshank and Sheehan 1964;Molnar-Perl et al 1987). Our findings (Table 1) support those of the above authors who concluded that for optimal esterification of all amino acids it was necessary to heat the reactants for 60 min.…”

Sample Preparation for Chromatographic Analysis

“…In a typical reaction the carboxylic acid is dissolved in an excess of an alcohol which contains a few percent of an acid catalyst, such as hydrogen chloride, acety1 chloride, thionyl chloride, boron trifluoride etherate, boron trichloride or an ion-exchange resin [487][488][489][490]. In a typical reaction the carboxylic acid is dissolved in an excess of an alcohol which contains a few percent of an acid catalyst, such as hydrogen chloride, acety1 chloride, thionyl chloride, boron trifluoride etherate, boron trichloride or an ion-exchange resin [487][488][489][490].…”