A Strategy for GC/MS Quantification of Polar Compounds via their Silylated Surrogates: Silylation and Quantification of Biological Amino Acids

Abstract

Substitution of polar functionalized compounds with silylated (e.g., trimethylsilylated) surrogates prior to GC/ MS analysis is a widely used analytical strategy. Calibration is a most demanding step of this strategy. In fact, a calibration function is usually acquired by converting known amounts of the pure analyte to its silylated surrogate using the same conditions employed for processing unknown samples. The cumbersome need of acquiring a new calibration function prevents, to a large extend, the possibility of modifying silylation and instrumental settings on a sample by sample basis as would be appropriate in a number of cases. The modified standard additions calibration method, suggested in this paper, overcomes this difficulty by integrating in a single analytical procedure calibration and sample analysis. Furthermore, the suggested procedure compensates for matrix effects which may be a serious source of inaccuracy and is a tool that can be used during method development in order to find the most suitable silylation conditions for a given analyte.The implementation and benefits of the modified standard additions calibration method are explored in this paper on the basis of a symbolic but enlightening experiment dealing with the very representative GC/MS quantification of biological amino acids via their trimethylsilylated derivatives. A Strategy for GC/MS Quantification of Polar Compounds via their Silylated Surrogates: Silylation and Quantification of Biological Amino AcidsMarco Guida 1 , Maria Michela Salvatore 1 and Francesco Salvatore 2 * 1 Dipartimento di Biologia, Università degli Studi di Napoli "Federico II", via Cintia, 21, Napoli, Italy 2 Dipartimento di Scienze Chimiche, Università degli Studi di Napoli "Federico II", via Cintia, 21, Napoli In practice, derivatization procedures are only an implementation of a general and very old principle of analytical chemistry according to which a substance to be analyzed is substituted by another substance (a surrogate) which is more easily determined than the original substance.In abstract, when a surrogate is substituted for the original analyte, calibration for quantitative analysis can take place according to one of two ways.If the surrogate is available as a pure substance and the degree of conversion of the original analyte to its surrogate is constant and known one can use pure solutions of the surrogate for calibration.On the contrary, if the surrogate cannot be isolated in a pure form and/or the degree of conversion of the original analyte to its surrogate is unknown and is dependent on the particular conditions under which substitution takes place, calibration must be performed by converting known amounts of the original analyte to its surrogate (using the same procedure employed for processing unknown samples).Because silylated compounds cannot be isolated and the efficiency of silylation procedures is usually unknown, calibration for quantitative GC/MS analysis via silylation takes always place by converting known amounts of the pure...

Impact of the Peptide WMR-K on Dual-Species Biofilm Candida albicans/Klebsiella pneumoniae and on the Untargeted Metabolomic Profile

“…After the incubation period, the culture supernatants were transferred into Eppendorf tube and centrifuged. The samples were completely dried with a stream of nitrogen, and the residues were treated with N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) (Fluka, Buchs, Switzerland) as previously described [59]. Each class comprises four biological replicates.…”