Gas Analysis Policy

by Kevin Kahmark (GHG Analyst) and G.P. Robertson (Lead Investigator)
Gas Sampling Analysis

The Robertson Lab maintains a gas analysis capability that we are happy to share with others conducting greenhouse gas flux measurements from soils. We are not a service lab and prioritize samples from collaborators, students, and those working on LTER, GLBRC, and related projects.  When capacity permits we accept samples from others. First point of contact for those interested in having samples analyzed is Kevin Kahmark, as described below.


  • Two Agilent 7890 Gas Chromatographs (GCs) with an FID (Flame Ionization Detector), ECD (Electron Capture Detector), and a Licor 820 – Infrared Gas Analyzer coupled to the GC (analog/digital signal transfer) for simultaneous N2O, CH4, and CO2 analyses. The combined lab capacity of the two instruments is approximately 50,000 samples (three gases per sample) per sampling season (April through November).  Each GC is coupled to a Gerstel MPS2XL autosampler with a custom sampling tray (see Figure 1 below) using Agilent Chemstation and Gerstel Maestro software, with results output to a .csv file.Analytical variability is less than 5% coefficient of variation (CV).  Twenty atmospheric samples are collected in the field and measured by the equipment above.  The resulting atmospheric concentrations are then statistically compared and commonly range from 1-3% coefficient of variation (CV) for each trace gas.
  • Each Gas Chromatograph has methodologies suitable for denitrification assays containing headspace C2H2.


  • The Agilent 7890 GC coupled with the Infrared Gas Analyzer measures N20, CH4, and CO2 concentrations of samples collected in a 6 ml over-pressurized vial. In general, four samples from a field static chamber provide adequate concentration data to calculate high-confidence atmospheric flux values for a given chamber. 
  • The concentration data (usually ppm by volume) are processed in a .csv file and returned to the investigator via email.
  • Calculation of flux is the responsibility of the investigator.
view of the GC autosampler.

Figure 1. One of two Agilent 7890 GCs with a Gerstel MPS2XL Autosampler coupled with a Licor 820 – Infrared Gas Analyzer to provide simultaneous analyses of N2O, CH4, and CO2.


  • Pilot samples to test experimental designs are usually run at no charge if the sample total is under fifty vials.
  • The MSU-approved sample cost for collaborators and MSU-based accounts is $4.00 per sample (for all 3 gases); the cost is otherwise $10.00 per sample.
  • Account information should be emailed to both the gas lab manager (Kevin Kahmark at and the KBS LTER project manager (Stacey Vanderwulp at The project manager will handle additional billing questions.

Requesting Analyses and Submitting Samples:

  • Please submit a work request via email to Kevin Kahmark ( Include the project scope, anticipated sample load and frequency, and start/end dates (approximate is fine).  The request should also include investigator and lead investigator contact information.
  • Any work being done on the KBS-LTER or KBS-GLBRC should have an approved SURF on file.
  • Labco 6ml vials and septa are required for analyses. Vials require over-pressurization for proper analysis (at least 10 mL of headspace gas per 6 mL vial). Vials are available from Labco Limited, Lampeter, United Kingdom and should be delivered in trays or boxes in a logical order.
  • Each vial should be clearly labeled and dated. Please attach an Excel or .csv table of all sample names in sequential order prior to delivering samples.
  • Samples can be delivered to:

Kevin Kahmark


3700 E Gull Lake Drive, Room 330

Hickory Corners, MI 49060


Manuscripts using data from analyzed samples should acknowledge this in the Acknowledgements section of manuscripts and dissertations; it is appropriate to acknowledge both K. Kahmark and G.P. Robertson for help with gas analyses. Co-authorship is not expected.