The SIF provides routine compound-specific ¹³C isotope analysis of a variety of compounds using GC-combustion isotope ratio mass spectrometry (GC-C-IRMS). Compound-specific ¹⁵N isotope analysis for some compounds is also available (e.g., amino acid derivatives). Compounds must generally be isolated from bulk sample materials, such as soils, sediments, or biological tissues, using multi-step preparative procedures prior to chromatographic analysis. Non-volatile organic compounds must be derivatized by silylation, alkylation, acylation, esterification or other methods in order to make them volatile and improve chromatographic separation. Examples can be found in the Thermo Scientific Pierce Reagents, Solvents and Accessories Handbook. Once separated chromatographically, each compound is entirely combusted to gases (CO₂, N₂) and subsequently introduced into the isotope ratio mass spectrometer. Analysis is performed using a Thermo GC/C-IRMS system composed of a Trace GC Ultra gas chromatograph (Thermo Electron Corp., Milan, Italy) coupled to a Delta V Advantage isotope ratio mass spectrometer through a GC/C-III interface (Thermo Electron Corp., Bremen, Germany). Compound identification support for the CSIA laboratory is provided by a Varian CP3800 gas chromatograph coupled to a Saturn 2200 ion trap MS/MS (Varian, Inc., Walnut Creek, CA U.S.A.).