This method applies to the measurement of volatile organic compounds (VOCs) as total gaseous nonmethane organics (TGNMO) reported as carbon in source emissions. It is not applicable for the determination of organic particulate matter. Organic particulate matter will interfere with the analysis, and, therefore, a particulate filter is required.
The sampling system consists of a heated probe, heated filter, condensate trap, flow control system, and sample tank. Samples are collected at a constant rate through the heated filter and chilled condensate trap by means of an evacuated sample tank. TGNMO is then determined by analyzing the condensate trap and sample tank fractions and combining the results.
The filter used is a glass fiber filter without organic binders and is not analyzed. It's used to remove organic particulate interferences. The condensate trap is U-shaped stainless steel. The trap will be kept in dry ice during sampling and should be kept on dry ice after collection and during shipment to the laboratory for analysis. The sample tank is cleaned and checked prior to use, is stainless steel, holds a minimum volume of 4L, and is evacuated to 10mm Hg absolute pressure or less.
Condensible organic material, Ccm, is measured in triplicate from the condensate trap and the average value reported. Nonmethane organic material (NMOC), Ctm, is measured in triplicate from the sample tank and the average value reported. TGNMO is the sum of the results of the condensate trap and sample tank which are converted to carbon.
If the samples are to be used to demonstrate compliance, the method requires an audit sample to be analyzed along with the field samples. The audit sample results must be within 20% of the accepted true value in order for the results to be considered valid.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | None specified in method. |
| Preservatives: | Keep the condensate trap packed in dry ice until the samples are returned to the laboratory for analysis |
| Required Preps: | Stainless steel condensate trap |
| Collection Method: | EPA Method 25: heated probe, heated filter, condensate trap, flow control system and sample tank |
| Analytical Methodology: | NMO Analyzer consisting of a GC equipped with an oxidation catalyst, a reduction catalyst and a FID by Method 25. |
| Documentation: | 
25
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Total Gaseous Nonmethane Organic Compounds | 50 |
ppm | ||
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.