Pyrolysis Compound Specific Isotope Analysis (Py-CSIA). Applications in natural and synthetic matrices.

Nowadays the study of isotopic signature of light elements through isotope ratio mass spectrometry (IRMS) is being extensively used to enlighten relevant scientific questions and important aspects for the geochemistry, environment and the industry i.e. global element cycles, past climatic conditions, paleodiets, trace food sources/webs, polymer signatures /traceability, etc. Thus, isotopic analysis has become a key tool for scientists in many disciplines and the practical applications of the technique are continuously growing. Compound-specific isotope analysis (CSIA) using gas chromatography-combustion/pyrolysis isotope ratio mass spectrometry (GC-EA/TC-IRMS), usually require intermediate preparative procedures prior to chromatographic analysis to isolate analytes from bulk samples i.e. soils, sediments, or other biological or synthetic materials. Non-volatile compounds must be made amenable to GC by derivatization or treated by different methods in order to be amenable to the chromatographic separation. Analytical pyrolysis is a long established technique ideally suited for one-stage combination with GC. The sample is heated up in an inert atmosphere to decompose into smaller units which are carried by a gas to the next instrument for separation and characterization. The pyrolyzer is usually linked to a GC which can further be connected to detectors such as MS or FTIR. In this communication the results obtained by effectively hyphenating analytical pyrolysis (Py-GC) with IRMS of light elements (C, H, N) stable isotopes are described. These include a variety of matrices of increasing complexity such as synthetic polymers, biopolymers from C3 and C4 photosystem plants, recent sediments, fossil materials, etc. First a bulk isotopic characterization of light elements (¿15N, ¿13C, ¿18O and ¿D) was performed for each material using a Flash 2000 HT elemental analyzer coupled to a Delta V Advantage IRMS (Thermo Scientific) (EA/TC-IRMS). Chemical structural information of pyrolysates released by the different matrices was first acquired by conventional analytical pyrolysis (Py-GC/MS). The direct study of specific compounds isotopic signature of light elements (¿13C, ¿15N and ¿D) was done by coupling a pyrolysis unit (double-shot pyrolyzer ¿Frontier Laboratories, model EGA/Py-3030D¿) ¿ to a gas chromatograph fitted with a flame ionization detector (GC/FID) and coupled to the Delta V Advantage IRMS (Thermo Scientific GC-Isolink System) (Py-GC-(FID)-EA\TC-IRMS).

Ministerio de Economía y Competitividad through project GEOFIRE (CGL2012-38655-C04-01) and Nicasio T. Jiménez-Morillo research grant BES-2013-062573.

Peer Reviewed