Targeted Metabolomics with DSI/DTD-GC-MS - an Overview

Helmut Geppert, Central Analytical Laboratory , Brandenburg University of Technology, Cottbus, Germany (h.geppert@gmx.de)
Thomas Fischer, Central Analytical Laboratory , Brandenburg University of Technology, Cottbus, Germany

A direct sample introduction device (DSI) was developed by Amirav and Dagan (1) and introduced as ChromatoProbe by Varian in 1997. It can serve as an introduction device for dirty untreated samples in any form of liquid, solid, powder or slurry. These include also body fluids and other human matrices such as urine, blood or plasma, hair, tissues and bacteria. Another option is to use a programmed temperature vaporizer (PTV) injector (so-called direct thermal desorption (DTD) interface) in combination with disposable microvials that fit inside an injection liner (ATAS-GL).

The DSI/DTD allows in-vial (in-liner) analytical derivatization.  Problems with the silylation are presented in more detail:  Koek et. al. (2)  reported , that an addition of pyridine hydrochloride solution increased the solubility of the underivatized metabolites and supported the silylation. We can demonstrate for the first time, that the addition of  ionic liquids also improve the in-vial silylation of organic acids (hydroxy fatty acids, citric acid).  

A direct thermal desorption (DTD) interface was previously used for the metabolic profiling of ultrasmall biological samples, for example 100 nl plasma and single cells (2).  The presentation shows first new results for the DSI-profiling of bacterial fatty acids for the rapid detection of human urinary tract infections and a comparison of   histopatological and metabolomic analysis of core biopsis (3).

(1) Amirav et al. (1997): A direct sample introduction device for mass spectrometry studies and GC-MS analysis".  Europ. Mass. Spectrom. 3, 105-111

(2) Koek et. al. (2010): Metabolic profiling of ultrasmall  sample volumes with GC/MS: from microliter to nanoliter samples.  Anal. Chem.  82, 156–162

(3) Brown et al. (2012): Cancer detection and biopsy classification using concurrent histopatological and metabolomic analysis of core biopsis. Genome Medicine 4, Article number 33