This method is for the determination of hydrogen sulfide (H2S) of fuel gas streams in petroleum refineries. The sample is collected at a constant sampling rate (1 L/min. for at least 10 minutes) in a series of midget impingers containing a cadmium sulfate absorbing solution. H2S is absorbed in the impinger solution, forming cadmium sulfide (CdS) which is measured titrimetrically.
The sampling train consists of a sampling valve, Teflon line, a series of five midget impingers, a silica gel drying tube and dry gas meter. The first impinger is filled with 15mL of 3% hydrogen peroxide (H2O2). The second impinger is left empty. Impingers 3-5 are filled with 15mL of the cadmium sulfate (CdSO4) absorbing solution. The CdSO4 is stable for one month after preparation.
After sampling, the contents of the H2O2 impinger are discarded. The contents of impingers 3-5 are combined in a glass-stoppered iodine flask along with the corresponding water rinse. Note that if a yellow film persists on the walls of the impingers then follow the alternate sample recovery procedures found in Section 11.2 of the method. An aliquot of the sample is prepared and analyzed via titration.
The method recommends titration of the sample as soon as possible and that the sample be kept away from direct sunlight after sample collection.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | Analyze as soon as possible and keep away from direct sunlight once collected. |
| Preservatives: | None specified in method. |
| Required Preps: | CdSO4 impinger solution |
| Collection Method: | Midget impinger sampling train following Method 11 procedures. |
| Analytical Methodology: | Titration |
| Documentation: | 
11
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Hydrogen sulfide | H2S |
7783-06-4 |
8 |
mg/m3 |
* 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.