Non-linear effects in the determination of paleotemperature U 37k′ alkenone ratios by chemical ionization mass spectrometry

R. Chaler, J. Villanueva, Joan O. Grimalt

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Resum

The performance of gas chromatography coupled to mass spectrometry in the positive chemical ionization mode using ammonia as reagent gas (GC-PCI-MS) in the analysis of C37 alkenones for paleotemperature estimation has been re-evaluated. In some conditions, the discrepancies observed in the measurement of the U37k′ index with this technique as compared with GC equipped with flame ionization detection (GC-FID) cannot be explained by differences in sensitivity between the tri- and diunsaturated alkenones. Thus, at low (currently <0.3) or high (currently >0.4) U 37k′ values the GC-PCI-MS determinations may be observed to be lower or higher, respectively, than those measured with GC-FID. As shown by analysis of a series of synthetic C37 alkenone standards these discrepant results can be explained by non linear effects in the GC-PCI-MS response factors. Second-order polynomial functions provide equations that describe better the signal to amount of analyte ratios. Users of GC-PCI-MS should calibrate their instruments with standards of known C37 alkenone composition in order to minimize non-linear effects.

Idioma originalEnglish
Pàgines (de-a)87-93
Nombre de pàgines7
RevistaJournal of Chromatography A
Volum1012
Número1
DOIs
Estat de la publicacióPublicada - 12 de set. 2003

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