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Landfill gas - Total non-methane organics & Nitrogen/OXYGEN 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.
The Tables above list the routine analytes reported for these methods. |
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