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Comunicación oral presentada en el 1st Iberian Meeting in Separation Sciences & Mass Spectrometry, XIX Conference of the Spanish Society of Chromatography and Related Techniques (SECyTA), IX Conference of the Spanish Society of Mass Spectrometry (SEEM), VI Conference of the Mass Spectrometry Group of the Portuguese Society of Chemistry (SPQ). Santiago de Compostela, October 8th-11th (2019)., Changes in climatic and environmental conditions can affect both, plant chemical and isotope composition. Nowadays, many studies use bulk isotope values, which represent a weighed mean average of the different plant compounds. An isotopic characterization of individual biogeochemical compounds is desirable in order to differentiate the isotopic composition of the main plant components. However, biomass is composed mainly of high MW biopolymers i.e. polysaccharides (celluloses), polypeptides (lignin), polypeptides (proteins), polyesters (waxes), etc. not amenable to most chromatographic techniques without the use of more or less previous intense extraction and sample preparation. Here, a particular analytical pyrolysis technique combining Py‐GC with a continuous flow isotope ratio mass spectrometer (IRMS) (Py‐CSIA) is described and validated. Isotopic values obtained by Py‐CSIA of standard n‐alkanes mixtures (dissolved C16 to C30 series with increasing concentrations along three pentads, Indiana Univ. SIL mix. Type B), fitted well to a straight line (R2 > 0.999). No induced thermal cracking nor deviations from the acclaimed isotope composition (fractionation) was observed up to high pyrolysis temperature (< 400 °C). Results linking detailed molecular and isotope composition obtained by the direct analysis of various biomass types and biopolymers will be discussed. In general, our results show that Py‐ CSIA can reveal major differences between biomass components from different biogenic origin with high precision. In addition, despite that biomass pyrolysates from different origins may yield very similar Py‐GC/MS patterns, Py‐CSIA can make the difference providing additional valuable isotopic information., Ministerio de Ciencia Innovación y Universidades” INTERCARBON project (CGL2016‐78937‐R). N.T. Jiménez‐Morillo and L. San Emeterio thanks the MICIU for funding FPI research grants (BES‐2013‐062573 and Ref. BES‐2017‐07968). Desiré Monis is acknowledged for technical assistance

Póster presentado en el 1st Iberian Meeting in Separation Sciences & Mass Spectrometry, XIX Conference of the Spanish Society of Chromatography and Related Techniques (SECyTA), IX Conference of the Spanish Society of Mass Spectrometry (SEEM), VI Conference of the Mass Spectrometry Group of the Portuguese Society of Chemistry (SPQ). Santiago de Compostela, October 8th-11th (2019)., In less than 50 years the area occupied by peat bogs in the Gulf of Cádiz (SW‐Spain) has been reduced by more than 90%. The peat bog studied here may well be considered as relict and one of the last and more Meridional still in existence in the Northern hemisphere. The vertical molecular composition of a 85 cm peat bog from Ribetehilo lagoon (Doñana National Park; SW‐Spain 37° 7'30.81"N; 6°37'50.19"O) is studied using analytical pyrolysis (Py‐GC/MS) and ultra‐high resolution mass spectrometry (ESI‐FT‐ICR/MS). The results obtained by the two techniques were similar, showing as shallow OC composition was dominated by fresh material from upper vegetation cover, while more transformed and humified material was accumulated in the bottom layers. This may be due to i) intense microbial activity combined with large fluctuations of the water table occurring during the year; and/or ii) anaerobic rocesses. In general, the lack of peat preservation in depth is probably a sign of bog degradation processes, probably linked with climate changes to which Mediterranean wetlands are particularly responsive., MICIU INTERCARBON Project (CGL2016‐78937‐R UE/FEDER). N.T. Jiménez‐Morillo and L. San Emeterio thanks the MICIU for funding FPI research grants (BES‐2013‐062573 and Ref. BES‐2017‐07968 UE/FEDER). Prof. P. Hatcher (Old Dominion Univ., USA) for advice and access to the COSMIC ESI‐FT‐ICR/MS instrument. Desiré Monis for technical assistance.