{"id":346,"date":"2023-06-07T10:50:29","date_gmt":"2023-06-07T17:50:29","guid":{"rendered":"https:\/\/dornsife.usc.edu\/feakins\/?page_id=346"},"modified":"2026-05-04T12:19:33","modified_gmt":"2026-05-04T19:19:33","slug":"irms-lab","status":"publish","type":"page","link":"https:\/\/dornsife.usc.edu\/feakins\/irms-lab\/","title":{"rendered":"IRMS Lab"},"content":{"rendered":"\n\n\n\n \n \n\n\n\n\n\n\n\n
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NEW INSTRUMENT NEWS!<\/h2>\n

Funded by NSF EAR-IF, our new Thermo 1610GC – GCIsolink II – ConfloIV – Delta Q<\/strong>\u00a0 is here!!! (March 2024)<\/p>\n

Installation was completed by 28th March 2024, and method and protocol development is underway.\u00a0 Qtegra is quite glitchy (so many reboots!) and we are looking forward to the promised software update in April, that will improve aspects of workflow. At the moment methods have to be built from scratch when making minor modifications, which is a frequent headache when optimizing methods for inlet and GC conditions. We are currently running standards and are excited to establish robust methods and workflows and to begin generating data. Here is Disha Baidya with her first compound specific carbon isotope measurement – and the first sample run on the new system – from Woranso-Mille, Ethiopia.<\/p>\n

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Funded by NSF EAR-IF, our new Thermo ISQ7610-NoVPI<\/strong>, with GC, FID and AS is here!!! (Oct 2023)<\/p>\n

Installation took >3 weeks, rather than 3 days, plus another couple of weeks for applications training and development, in total ~half of the semester – setting up lab instrumentation takes time! Now things are running well (end of October 2023). Here’s the proud team responsible for getting the first methods, workflows and kinks of a new system worked out – we did it!! Samples and number crunching fun is happening!!<\/p>\n

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Instrumentation in the Feakins lab<\/strong><\/h3>\n

GC-IRMS<\/strong>\u00a0\u2013 Gas Chromatography Isotope Ratio Mass Spectrometry
\nWe now use a brand new 2024 Thermo Scientific 1610GC equipped with a Rxi\u00ae-5ms (30m x 0.25mm, film thickness 1mm); a PTV inlet; a TriPlus autosampler; connected via GC Isolink II with parallel combustion furnace (at 1000 \u00b0C) and pyrolysis furnace (at 1420 \u00b0C) together with a Conflo IV to a Delta Q mass spectrometer. Combustion is used for the analysis of 13C\/12C and pyrolysis is used for the analysis of D\/H.<\/p>\n

GC-MS\/FID<\/strong>\u00a0\u2013 Gas Chromatography \u2013 Mass Spectrometry \u2013 Flame Ionization<\/p>\n

We now use a brand new 2023 Thermo 1610GC equipped with a AS1610 programmable injector, a Rxi\u00ae<\/sup>-5ms column (30m x 0.25mm, film thickness 0.25mm); an FID flame ionization detector; and connected to a ISQ7610 (intelligent single quadrupole) mass spectrometer. The MS provides mass spectral information for biomarker identification and FID provides quantification.<\/p>\n

We used to use (2008-2023, retired 2023 at ~25 yrs old) a Agilent 6890 GC equipped with a Rxi\u00ae<\/sup>-5ms (30m x 0.25mm, film thickness 0.25mm); and a 7683 programmable injector connected to an Agilent 5973 MSD mass spectrometer and an FID flame ionization detector. The Agilent GC-MS provides mass spectral information for biomarker identification and FID provides quantification.<\/p>\n

Preparative facilities in the Feakins lab<\/strong><\/h3>\n

Freeze-drying sediments
\n<\/strong>New, summer 2023!\u00a0We have a Labconco benchtop 2.5L freeze dryer with an oil-free scroll pump.<\/p>\n

We have a Virtis 2k freeze dryer, including secondary cold trap (organic clean) to dry sediment and plant tissue prior to solvent extraction.<\/p>\n

Cryogenic Vacuum Line Extraction
\n<\/strong>We have a vacuum line and offline batch distillation apparatus, to enable efficient extraction of plant leaf waters.<\/p>\n

Solvent Extraction<\/strong>
\nWe use Accelerated Solvent Extraction (ASE) by Dionex Corporation, which completes solvent extraction and filtration under high temperature (100\u00b0C) and pressure (1500psi).<\/p>\n

Virtual Tour of the Lab<\/strong><\/h3>\n

Dornsife video:\u00a0Tap the Past to Map the Future<\/a><\/strong>\u00a0(3 mins)<\/p>\n

Method development<\/h1>\n

Resources that we have developed for compound specific isotopic analysis are shared here.<\/p>\n

Protocols for lignin methoxy quantification
\n<\/strong><\/h3>\n
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  1. Zeisel method for methoxy cleavage and liquid-liquid extraction of product for quantification.\u00a0SOP1<\/a><\/li>\n
  2. Lignin phenol calibration for quantification of methoxy in lignin substrates.\u00a0SOP2<\/a><\/li>\n<\/ol>\n

    If you use these protocols, please cite:<\/p>\n

    Lee, H., X. Feng, M. Mastalerz, and S. J. Feakins (2019), Characterizing lignin: Combining lignin phenol, methoxy quantification, and dual stable carbon and hydrogen isotopic techniques,\u00a0Organic Geochemistry,\u00a0136, 103894.<\/p>\n

    How to derivatize fatty acids for CSIA work?
    \n<\/strong><\/h3>\n

    To derivatize fatty acids e.g. long chain n-alkanoic acids for GC work we methylate the fatty acids to fatty acid methyl esters. To do so, we use HCl and\u00a0methanol*<\/strong>, for more information, read a paper by Hyejung Lee and co-authors\u00a0Lee et al., 2017, RCM.<\/a><\/p>\n

    *Purchase a batch of GC-grade methanol for derivatization (4L), bottle it in aliquots (we use 500 mL bottles) and teflon tape to seal. Mark it for isotope use only, not general lab use. Find out the isotopic composition of the methyl in the methanol by derivatizing a known standard.\u00a0\u00a0Phthalic acid<\/a>\u00a0of known isotopic composition can be acquired from A. Schimmelmann, U. Indiana (many OG stds\u00a0here<\/a>). But wait, it\u2019s not that easy!!<\/p>\n

    Methylation of phthalic acid<\/strong>\u00a0requires more care and skill, and slightly different protocols, than long chain (e.g. leaf wax) FAME preparation, see Hyejung\u2019s\u00a0protocol<\/strong><\/a>\u00a0accompanying her paper that should guide you to success. NB. Beware evaporation of your PAME product. Good luck!!<\/p>\n

    Then you can correct your FAME CSIA data for the added methyl group to determine the value of the FA. It is all in the paper:\u00a0full RCM article here.<\/a><\/p>\n

    Make your own combustion reactor<\/strong><\/h3>\n