This method applies to the determination of chromium (Cr) in emissions from decorative and hard chrome electroplating facilities, chromium anodizing operations, and continuous chromium plating operations at iron and steel facilities. Samples can be analyzed for total chromium via ICP or GFAA and for hexavalent chromium via IC-PCR.
Samples are collected isokinetically from a source using a modified Method 5 train consisting of a unheated glass probe and liner and a series of impingers. No filter is required and there should be no metal parts in the sampling train. Per the method, sample for a minimum of 2 hours. The sampling procedures are a little different for the collection of total Cr versus hexavalent Cr.
For Total Cr sampling, the first two impingers are filled with 100mL of 0.1N NaOH or 0.1N NaHCO3 (sodium bicarbonate), the third impinger is left empty, and the fourth impinger is filled with 200-300g of silica gel. Once the sample has been collected, the volume of the contents of impingers 1-3 and the silica gel impinger is measured to determine the moisture content of the stack gas. The contents of impingers 1-3 are combined along with the impinger and connecting glassware rinse in a polyethylene or polypropylene container. Use the impinger solution selected for sampling for the rinse. The samples do not have to be refrigerated. Samples can be analyzed by ICP (inductively couple plasma spectrometry) or GFAA (graphite furnace atomic absorption spectroscopy) for Total Cr. Samples for ICP analyses require no further preparation. Samples for analysis via GFAA are digested with nitric acid (HNO3).
For Hexavalent Cr sampling, the first two impingers are filled with 100mL of 0.1N NaOH or 0.1N NaHCO3 (sodium bicarbonate), the third impinger is left empty, and the fourth impinger is filled with 200-300g of silica gel. Once the sample has been collected, the pH of impinger 1 is measured using a pH strip. The pH must be >8.5 for a NaOH impinger solution or > 8.0 for a NaHCO3 impinger solution. If the pH doesn't meet this criteria, then the sample must be discarded and resampled increasing the normality of the impinger solution to 0.5N. If the pH is within requirements then measure the volume of the contents of impingers 1-3 and the silica gel impinger to determine the moisture content of the stack gas. The contents of impingers 1-3 are combined along with the impinger and connecting glassware rinse in a polyethylene or polypropylene container. Use the impinger solution selected for sampling for the rinse. The samples are to be refrigerated during shipping and storage. The pH of the sample is measured and then the sample is filtered. The filter is retained for Total Cr analysis if required. The filtrate is analyzed using IC/PCR (ion chromatography with a post column reactor).
If the sample data are to be used for compliance purposes, the method requires that an audit sample be obtained and submitted with the samples to the laboratory for analysis.
This method is similar to SW-846 0061/7199 for Hexavalent Cr.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | 60 days from sampling to analysis for Cr only and 14 days from sampling to analysis for Hexavalent Cr. |
| Preservatives: | No refrigeration required for Cr only. Ship and store samples at 4°C for Hexavalent Cr. |
| Required Preps: | None specified in method. |
| Collection Method: | Modified Method 5 sampling train following Method 306 procedures. |
| Analytical Methodology: | ICP or GFAA for Cr and IC/PCR for Hexavalent Cr |
| Documentation: | 
306
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Hexavalent chromium | Cr+6 |
18540-29-9 |
0.5 |
ug/L |
| Chromium | Cr |
7440-47-3 |
5 |
µg/L |
* 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.