Natural additives in active food packages. Pyrolysis compound Specific isotope analysis (Py‐CSIA)

Abstract

Isotope ratio mass spectrometry (IRMS) has become a key tool for scientists in many disciplines and the practical applications of the technique are continuously growing. While no or little sample preparation is required for bulk isotopic analyses, for compound‐specific isotope analysis (CSIA) usually intermediate preparative procedures are required prior to chromatographic analysis to isolate analytes from geological, biological or synthetic materials. In addition, non‐volatile compounds must be made amenable to GC by derivatization or treated before chromatographic separation adding complication. Analytical pyrolysis is a long established technique that can help overcome preparative manipulation of samples. The sample is heated up in an inert atmosphere (usually He) to decompose into smaller units (pyrolysate) which are transferred for chromatographic separation to a GC connected to an appropriate detector. In this communication we describe the results obtained by hyphenating analytical pyrolysis (Py‐GC) with carbon IRMS for the analysis of a polylactic acid (PLA) based film extruded with variable quantities of natural plant extracts or essential oils for use in active food packaging. Chemical structural information of pyrolysates was first determined by conventional analytical pyrolysis (Py‐GC/MS). Bulk δ13C measures were performed for each material by EAIRMS. The direct study of δ13C carbon isotopic signature in specific compounds was done by coupling a pyrolysis unit to a gas chromatograph connected (via Thermo Scientific GC‐Isolink System) to a continuous flow IRMS unit (Py‐GC‐(FID)‐EA‐IRMS). Using this Py‐CSIA device it was possible to trace natural additives with light δ13C signatures derived from C3 photosystem vegetation, from the heavier bio‐plastic backbone usually derived from corn (C4 vegetation) starch. Finally the results are discussed in terms of the potential of this new chromatographic application for food traceability and security.