This method is for the collection and analysis of formaldehdye and acetaldehyde from stationary source emissions developed by the California Air Resources Board (CARB). Samples are collected using a heated probe (stainless steel or quartz), vacuum pump, rotometer, a Teflon sampling line, two impingers filled with 10mL of 2,4-dinitrophenylhydrazine (DNPH), and a silica gel impinger. The DNPH reagent derivatizes the aldehydes and ketones in the gas stream. Per the method, 4 field blanks must be generated and analyzed. The results of the field blanks are used to establish the background level of formaldehyde and acetaldehyde. The background level is then subtracted from the results of the field samples.
Once sampling is completed the sampling line is rinsed with DNPH solution and added to the contents of the first impinger. The contents of the second impinger are kept in a separate container as each impinger is analyzed separately. Each impinger is rinsed with 2mL of DNPH reagent followed by 1mL of reagent water. The rinse contents are combined with the appropriate impinger container. The impingers are extracted with hexane/methylene chloride, solvent exchanged to acetonitrile and analyzed using reverse phase high performance liquid chromatography (HPLC) with ultraviolet (UV) detection to identify and quantitate the target analytes.
The DNPH reagent should be kept cool after preparation and stored in amber glass bottles. The method allows for extraction within 7 days from sample collection but specifies that extraction should occur as soon as possible.
Note that this method has not been validated for gas streams with high particulate or moisture loading.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | 2 days from the preparation of the DNPH solution to sample collection, 7 days from sample collection to extraction and 30 days from extraction to analysis. |
| Preservatives: | Cool samples after collection and for shipment to the laboratory. |
| Required Preps: | 2,4-DNPH impinger solution |
| Collection Method: | Midget impinger sampling train following CARB 430 procedures. |
| Analytical Methodology: | Reverse phase HPLC/UV |
| Documentation: | 
430
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Formaldehyde | CH2O |
50-00-0 |
1 |
ppm |
| Acetaldehyde | C2H4O |
75-07-0 |
1 |
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.