Analytica Chimica Acta 536 (2005) 283–293 Characterization of microorganisms by thermogravimetric analysis–mass spectrometry A. Peter Snyder a,∗ , Ashish Tripathi b , Jacek P. Dworzanski b , Waleed M. Maswadeh a , Charles H. Wick a a Research and Technology Directorate, Edgewood Area Aberdeen Proving Ground, Aberdeen, MD 21010-5424, USA b Geo-Centers, Inc., Edgewood Area, Aberdeen Proving Ground, Aberdeen, MD 21010-5424, USA Received 13 September 2004; received in revised form 14 December 2004; accepted 14 December 2004 Available online 25 January 2005 Abstract A thermogravimetric analysis (TGA) system was interfaced to a mass spectrometry (MS) detector to investigate the thermal evolution of decomposition products from microorganisms. Traditionally, TGA–MS has been used to investigate the thermal parameters and chemical composition of materials such as the coal and lignin energy producing compounds and a wide range of technical organic polymers. The relative weight loss of biochemical species and compounds in bacteria from the TGA system allowed a comparison to the relative amounts of the same substances in bacteria from conventional microbiological extraction and isolation techniques. MS is shown to produce information rich total ion chromatogram profiles of thermal products from biochemical standards and microorganisms. The TGA thermal weight loss chromatogram (TWC) provides a degree of resolution, because the bacterial biochemical substances and components partition in a temporal fashion. Standard biochemical substances such as dipicolinic acid, polyhydroxybutyric acid, and peptidoglycan are produced in the same general temperature region in the TWC profile, and the compounds have similar mass spectra compared to those from microorganisms. Characterization of microorganisms was possible by the relation of their thermal events and extracted mass spectra to those of low and high mass model biochemical compounds. © 2004 Elsevier B.V. All rights reserved. Keywords: Gram-positive bacteria; TGA–MS; Thermogravimetric analysis; Mass spectrometry; Thermal programming; Biomarkers; Bacillus 1. Introduction Thermal analysis is a convenient processing technique for the transformation of relatively large substances into com- pounds suitable for analysis by mass spectrometry (MS) instrumentation. Thermal processing can be performed by linear programming to impose a defined heating gradient in the minutes timeframe. Temperatures in the 300–800 ◦ C range are used for bond breakage and fractionation of a sub- stance into entities for MS detection and potential identifi- cation [1,2]. Rapid heating, or pyrolysis, can provide high temperatures for bond breakage of a sample in the seconds ∗ Corresponding author. Tel.: +1 410 436 2416; fax: +1 410 436 1912. E-mail address: apsnyder@apgea.army.mil (A.P. Snyder). timeframe [3,4]. Therefore, while slow heating provides high resolution of product evolution envelopes, a rapid heating rate produces a relatively poorer resolution of product distribution envelopes. Bacteria have been investigated by Py-MS for individual biochemical constituents [5,6]. These compounds provide various degrees of biological characterization and iden- tification capabilities with respect to the identity of the microorganism. Patterns of masses contain fundamental in- formation such as the carbohydrate and protein components. Individual compounds can also yield distinctive informa- tion that relate to Gram-positive and Gram-negative mi- croorganism status. Pyrolyzate compounds directly related to these two taxonomic microbiological groups and detected by MS include dipicolinic acid (DPA) and picolinic acid [7,8], 0003-2670/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2004.12.036