This method is used for the determination of sulfuric acid (including sulfuric acid mist and sulfur trioxide) and gaseous sulfur dioxide emissions from stationary sources. Samples are collected isokinetically onto a filter and impinger solutions. The sulfuric acid and sulfur dioxide are separated and both fractions are measured separately by the barium-thorin titration method. It is also possible to determine filterable particulates by using a heated glass fiber filter for collection.
A modified Method 5 train consisting of a probe, filter, and series of impingers is used for collection. The differences from a standard Method 5 train are the use of a non-heated filter (unless particulates are going to be determined) and placing the filter holder between the first and second impingers. The first impinger is filled with 100mL of 80% isopropanol, the second and third impingers with 100mL of 3% hydrogen peroxide (H2O2), and the fourth impinger is filled with 200g of silica gel.
Once the sample has been collected, the contents of all the impingers are weighed if a moisture determination will be made. Container 1 consists of the contents of the first impinger and rinses of the probe, first impinger, connecting glassware before the filter and the front half of the filter holder. The rinse is made with 80% isopropanol. The filter is added to Container 1 which is diluted to a volume of 250mL with 80% isopropanol. Container 2 consists contents of impingers two and three and rinses of the impingers, connecting glassware and back half of the filter holder. The rinse is made with water. The contents of Container 2 are diluted to a volume of 1000mL with water.
An aliquot is taken from Container 1, a thorine indicator added and it is titrated with a barium standard. A separate aliquot is taken and the titration repeated. The average value of the replicates is reported and they must agree within 1% or 0.2mL whichever is greater. The same process is repeated with Container 2.
If the data are to be used for compliance with source emission regulations then the method requires the analysis of an audit sample along with the collected field samples. In order for the audit to pass, the method cites an agreement within 5% from the value determined in the analysis to the accepted true concentration of the audit sample.
Known interferences with this method include fluoride, free ammonia, and dimethyl aniline.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | None specified in method. |
| Preservatives: | None specified in method. |
| Required Preps: | Glass fiber or quartz filter, pre-tare the filter if particulates are to be measured. |
| Collection Method: | Modified Method 5 train following Method 5 and 8 procedures. |
| Analytical Methodology: | Barium-thorium Titration |
| Documentation: | 
8
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Sulfur dioxide | SO2 |
7446-09-5 |
1.2 |
mg/m3 |
| Sulfur trioxide | SO3 |
7446-11-9 |
0.05 |
mg/m3 |
| Sulfuric acid | H2SO4 |
7664-93-9 |
0.05 |
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.