Hexamethyldisilazane and perfluorocarboxylic acid couples achieve trialkylsilylation and acylation of active proton containing organics in a single step

Abstract

A novel, multifunctional group mediated one-step derivatization (MGOD) method has been developed employing the couples of hexamethyldisilazane (HMDS) and perfluorocarboxylic acid (PFCA).11{couples are: HMDS & trifluoroacetic acid (TFA) or HMDS & pentafluoropropionic acid (PFPA) or HMDS & heptafluorobutyric acid (HFBA)} (henceforth: HMDS & PFCAs). MGOD relies on the unique reactivity of HMDS and PFCA to provide simultaneous trialkylsilylation and acylation in a single step. While primary aliphatic amines and diamines are generally nonreactive (certainly secondary and tertiary amines are nonreactive either), MGOD allows for trialkylsilylation of amino acids (AAs), amino alcohols, amino sugars, 2,6-diaminoheptanedioic acid, di- and tripeptides, and in turn moderates the basicity of their free amino groups and facilitates subsequent acylation. The identification, quantification and stoichiometry of MGOD were characterized by selective mass fragmentations and monitoring by GC–MS. Reaction conditions were optimized and analytical performance characteristics were established with respect to a reproducibility of 5.6 RSD%, a linearity of R2 = 0.996 and limit of quantitation values (LOQ) of 41–75 pg/μL. Derivatives were prepared without preliminary extraction steps, avoiding the use of organic solvents. The practical utility of MGOD was evidenced by derivatization of amino acids in a branched- chain amino acid (BCAA), nutritional supplement (recovery data of standard addition to BCAA varied between 92 and 110%.), in 100, 200 and 300 µL volumes of human urine demonstrating the proportionality of the method, and in peptide hydrolysates.