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    STUDIA GEOLOGIA - Issue no. 1 / 2007  
         
  Article:   DEVELOPMENT OF THE NANO-EA-IRMS: A NOVEL METHOD FOR ANALYZING THE ISOTOPIC COMPOSITION OF LARGE ORGANIC COMPOUNDS.

Authors:  COURTNEY TURICH, PRATIGYA POLISSAR, JAMEY FULTON, ADRI VAN DUIN, KATHERINE H. FREEMAN. 		 
       
         
  Abstract:  Existing methods for the compound-specific stable isotope analysis (CSIA) require introduction of individual compounds to an isotope ratio mass spectrometer via gas (GC) and liquid chromatographic (LC) interfaces. While these methods are robust, there are limitations on the size and polarity of analyzable compounds. To measure the isotopic composition of a broader range of compounds (especially tetraether membrane lipids and pigments), we developed a system to reduce the minimum sample size using elemental analysis mass spectrometry (EA-irMS) of individual compounds. EA-irMS sample size requirements are artificially high because high carrier gas flow rates effectively dilute the sample gas. To take advantage of the universal applicability of EA-irMS, we have designed a system to reduce sample size requirements by cryogenically trapping sample gas (CO2, N2, H2, and CO) from the high-flow EA effluent on a custom 0.75 ID silicosteel trap packed with 5Å MolSieve (Restek, Bellefonte, PA USA). The sample gas is then diverted to a low-flow helium stream (1 ml/min), thus reducing the carrier gas:sample gas ratio.  
         
     
         
         
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