1. Background

Scope

For background information on trace metals, see CF58.

This Combustion File (CF) describes how to recover samples taken from a stack when testing for trace metals and particulates, using a sampling train and sampling methodology conforming to the US EPA Method 29: Determination of Metal Emissions from Stationary Sources. It also covers the cleanup of the sampling train. CFs 207 and 208 cover the set up of the sampling train and the sampling itself. A diagram of the sampling train is available in CF206. CFs 204 and 205 provide information on how to select traverse points for sampling.

Safety

This CF does not cover safety procedures. The reader should consult other safety literature and particularly local safety regulations before performing the acquisition of the sample.

Equipment

The equipment used in the recovery and cleanup of the sample is described in CF206.

2. Cleanup

Begin cleanup as soon as the probe has been removed from the stack at the end of the sampling period. Allow the probe to cool prior to sample recovery.

1.        When it can be safely handled, wipe off all the external particulate matter near the tip of the probe, and place a rinsed, non-contaminating cap over the nozzle, in order to prevent losing or gaining particulate matter. Do not cap the probe tip tightly while the sampling train is cooling – a vacuum can form in the filter holder, drawing liquid from the impingers into the filter.

2.       Before moving the sampling train to the cleanup site, remove the probe from the sampling train and cap the open outlet. Ensure that no condensate is lost while doing so.

3.       Cap the filter inlet where the probe was fastened.

4.       Remove the umbilical cord from the last impinger and cap the impinger. Cap the filter holder outlet and impinger inlet. Use non-contaminating caps, whether ground-ground-glass stoppers, plastic caps, serum caps, or Teflon tape to close these openings.

5.       Transfer the probe and filter-impinger assembly to a cleanup area that is clean and protected from the wind and other potential causes of contamination or loss of sample.

6.       Inspect the train before and during disassembly and note any abnormal conditions. Take special precautions to assure that all the items necessary for recovery do not contaminate the samples.

3. Sample Recovery

General Principles

¨        Do not use any metal-containing materials when recovering this train.

¨        When using a specified amount of cleaning fluid (e.g. 100ml acetone), use exactly and only that amount, as this is necessary for subsequent blank correction procedures.

¨        It is recommended that two people clean the probe, to minimize sample losses.

¨        Between sampling runs, keep brushes clean and protected from contamination.

¨        Due to the potential reaction of KMnO₄ with acid, pressure build-up can occur in the sample storage bottles. Do not fill these bottles completely and take precautions to relieve excess pressure.

¨        When dealing with permanganate: To prevent the autocatalytic decomposition of the permanganate solution, filter the solution through Whatman 541 filter paper (available at most scientific stores).

¨       Measurements of impinger volumes are required for the determination of the stack gas moisture content.

Method

1.        Container 1 (Sample Filter) – Carefully remove the filter from the filter holder and place it in its labelled petri dish container. To handle this filter, use either acid-washed polypropylene or Teflon coated tweezers or clean, disposable surgical gloves rinsed with water and dried. If it is necessary to fold the filter, make certain that the particulate cake is inside the valley of the fold. Carefully transfer the filter and any particulate matter or filter fibres that adhere to the filter holder gasket to the petri dish by using a dry (acid cleaned) nylon bristle brush. Seal the labelled petri dish.

2.       Container 2 (Acetone Rinse) – Perform this procedure only if a determination of particulate matter is to be made. Quantitatively recover particulate matter and any condensate from the probe nozzle, probe fitting, probe liner, and front half of the filter holder by washing these components with a total of 100ml of acetone, while simultaneously taking great care to see that no dust on the outside of the probe or other surfaces gets in the sample.

Clean the inside surfaces by rinsing with acetone from a wash bottle while brushing with a non-metallic brush. Brush until the acetone rinse shows no visible particles, then make a final rinse of the inside surface with acetone.

Carefully remove the probe nozzle, and clean the insides, then do the sample-exposed inside parts of the probe fitting. Rinse the probe liner with acetone by tilting and rotating the probe while squirting acetone into its upper end so that all inside surfaces will be wetted with acetone. Allow the acetone to drain from the lower end into the sample container.

A funnel may be used to aid in transferring liquid washings to the container.

Follow the acetone rinse with a non-metallic probe brush. Hold the probe in an inclined position squirt acetone into the upper end as the probe brush is being pushed with a twisting action three times through the probe. Hold a sample container underneath the lower end of the probe, and catch any acetone and particulate matter being brushed through the probe.

Rinse the brush with acetone, and quantitatively collect these washings in the sample container. After the brushing, make a final acetone rinse of the probe as described above.

Clean the inside of the front half of the filter holder in the same manner. After all acetone washings and particulate matter have been collected in the sample container, tighten the lid so that acetone will not leak out when shipped to the lab. Mark the height of the fluid level to determine whether or not the leakage occurred during transport. Clearly label the container to identify its contents.

3.       Container No. 3 (Probe Rinse – HNO₃). Keep the probe components clean and free from contamination (including dust) during the probe rinse. Rinse the probe nozzle and fitting, probe liner, and front-half of the filter holder thoroughly with a total of 100 ml of 0.1 N HNO₃, and place the wash into a sample storage container.

Follow the same procedure as with acetone, but with the 0.1 N HNO₃.

Record the volume of the rinses. Mark the height of the fluid level on the outside of the storage container and use this mark to determine if leakage occurs during transport. Seal the container, and clearly label the contents.

Finally, rinse the nozzle, probe liner, and front-half of the filter holder with water followed by acetone, and discard these rinses.

4.       Container No. 4 (Impingers 1 through 3, Moisture Knockout Impinger, when used, HNO₃/H₂O₂ Impingers Contents and Rinses). Due to the potentially large quantity of liquid involved, the tester may place the impinger solutions from impingers 1 through 3 in more than one container, if necessary. Measure the liquid in the first three impingers to within 0.5 ml using a graduated cylinder. Record the volume. Clean each of the first three impingers, the filter support, the back half of the filter housing, and connecting glassware by thoroughly rinsing with 100 ml of 0.1 N HNO₃. Rotate and agitate each impinger, so that the impinger contents might serve as a rinse solution.

Pour approximately 30 ml of 0.1 N HNO3 into each of the first three impingers and agitate the impingers. Drain the 0.1 N HNO3 through the outlet arm of each impinger into Container No. 4. Repeat this operation a second time; inspect the impingers for any abnormal conditions.

Rinse each piece of glassware twice with 0.1 N HNO3; transfer this rinse into Container No. 4. Do not rinse or brush the glass-fritted filter support. Measure and record the total amount of 0.1 N HNO3 used for rinsing.

Combine the rinses and impinger solutions, measure and record the final total volume. Mark the height of the fluid level, seal the container, and clearly label the contents.

5.       Container Nos. 5A (0.1 N HNO₃), 5B (KMnO₄/H₂SO₄ absorbing solution), and 5C (8 N HCl rinse and dilution). When sampling for Hg, pour all the liquid from the impinger (normally impinger No. 4) that immediately preceded the two permanganate impingers into a graduated cylinder and measure the volume to within 0.5 ml. Place the liquid in Container No. 5A. Rinse the impinger with exactly 100 ml of 0.1 N HNO3 and place this rinse in Container No. 5A.

Pour all the liquid from the two permanganate impingers into a graduated cylinder and measure the volume to within 0.5 ml. Place this acidic KMnO₄ solution into Container No. 5B. Using a total of exactly 100 ml of fresh acidified KMnO₄ solution for all rinses (approximately 33 ml per rinse), rinse the two permanganate impingers and connecting glassware a minimum of three times. Pour the rinses into Container No. 5B, carefully assuring transfer of all loose precipitated materials from the two impingers. Similarly, using 100 ml total of water, rinse the permanganate impingers and connecting glass a minimum of three times, and pour the rinses into Container 5B, carefully assuring transfer of any loose precipitated material. Mark the height of the fluid level, and clearly label the contents.

If no visible deposits remain after the water rinse, no further rinse is necessary. However, if deposits remain on the impinger surfaces, wash them with 25 ml of 8 N HCl, and place the wash in a separate sample container labeled No. 5C containing 200 ml of water. First, place 200 ml of water in the container. Then wash the impinger walls and stem with the HCl by turning the impinger on its side and rotating it so that the HCl contacts all inside surfaces. Use a total of only 25 ml of 8 N HCl for rinsing both permanganate impingers combined. Rinse the first impinger, then pour the actual rinse used for the first impinger into the second impinger for its rinse. Finally, pour the 25 ml of 8 N HCl rinse carefully into the container. Mark the height of the fluid level on the outside of the container to determine if leakage occurs during transport.

6.       Container No. 6 (Silica Gel). Note the colour of the indicating silica gel to determine whether it has been completely spent and make a notation of its condition. Transfer the silica gel from its impinger to its original container and seal it. The tester may use a funnel to pour the silica gel and a rubber policeman to remove the silica gel from the impinger. The small amount of particles that might adhere to the impinger wall need not be removed. Do not use water or other liquids to transfer the silica gel since weight gained in the silica gel impinger is used for moisture calculations. Alternatively, if a balance is available in the field, record the weight of the spent silica gel (or silica gel plus impinger) to the nearest 0.5 g.

7.       Blanks. At least once during each field test, blanks must be prepared as follows. Seal the labelled (with container number) container after the blank has been made.

a.       8.2.11 Container No. 7 (Acetone Blank). If particulate emissions are to be determined, place a 100-ml portion of the acetone used in the sample recovery process into a container.

b.       8.2.12 Container No. 8A (0.1 N HNO3 Blank). Place 300 ml of the 0.1 N HNO3 solution used in the sample recovery process into a container.

c.       8.2.13 Container No. 8B (Water Blank). Place 100 ml of the water used in the sample recovery process into a container.

d.       8.2.14 Container No. 9 (5 Percent HNO3/10 Percent H2O2 Blank). Place 200 ml of the 5 Percent HNO3/10 Percent H2O2 solution used as the nitric acid impinger reagent into a container.

e.       8.2.15 Container No. 10 (Acidified KMnO4 Blank). Place 100 ml of the acidified KMnO4 solution used as the impinger solution and in the sample recovery process into a container. Prepare the container as described in Step 5. 

f.       8.2.16 Container No. 11 (8 N HCl Blank). Place 200 ml of water into a sample containe. Then carefully add with stirring 25 ml of 8 N HCl. Mix well and seal the container.

g.       8.2.17 Container No. 12 (Sample Filter Blank). Place into a petri dish three unused blank filters from the same lot as the sampling filters. Seal the petri dish.

4. What next?

After the sample has been recovered, it is ready for analysis. Analysis is not covered in this series of CFs. Independent laboratories can be used for analysis after the sample has been taken. The data collected during sampling should be provided to the analysis laboratory so that concentrations can be calculated.

Sources

[1] US EPA, US EPA Method 29: Determination Of Metals Emissions From Stationary Sources, US Federal Registry.

[2] US EPA, US EPA Method 2: Determination Of Stack Gas Velocity and Volumetric Flow Rate, US Federal Registry.

[3] US EPA, US EPA Method 5: Determination Of Particulate Matter Emissions From Stationary Sources, US Federal Registry.

[4] US EPA, US EPA Method 12: Determination Of Inorganic Lead Emissions From Stationary Sources, US Federal Registry.