ASTM D1946 & EPA 25c/3c – Fixed Gases and TNMOC
An evacuated stainless-steel canister is used to collect the sample. A sampling probe is punched into the landfill cap and a canister is attached to a sample line extending from the probe. The canister vacuum then draws in gases generated by the landfill through a flow controller. The canister is pressurized with helium in the laboratory prior to analysis.
For analysis the canister is attached to our custom analytical instrument and a sample loop is filled with sample. On injection the sample is swept into a GC. Using a series of valves and the method required Unibead/Carboseive G columns, methane and carbon dioxide are allowed to elute from the columns, after which the remaining sample is backflushed, oxidized and reduced to methane to be detected by the flame ionization detector as one chromatographic peak. Simultaneously, a second sample loop is injected and analyzed by the thermal conductivity detector for the quantification of nitrogen and oxygen.
EPA Method 25C dictates that the system be calibrated against propane, reported as parts per million as carbon, and then correct results for nitrogen and moisture. The quality control of EPA 25C includes triplicate analysis at each level of the calibration curve, triplicate analysis of the samples, analysis of a method blank, and analysis of a daily standard. EPA 3C requires daily standards, method blanks, and duplicate analyses of samples.
Many processes require the determination of oxygen, carbon dioxide, methane, and nitrogen. Air Technology has the capability to perform these analyses. Procedures are similar to those of the TNMOC analysis described previously. A sample is introduced into the GC/FID/TCD system via a sample loop injector and through a series of valves and special columns; then the analytes of interest are detected. Quality control procedures follow those described in EPA Method 3C and ASTM D1946.
General Chemistry table lists the analytes and reporting limits (RLs) for methods EPA 25C/3C and ASTM D1946 for standard analysis.
The analysis of non-target analytes is also available.