EPA Method 26

Hydrogen Chloride (HCl);
Hydrogen Fluoride (HF);
Hydrogen Bromide (HBr);
Bromine (Br₂);
Chlorine (Cl₂)
Can also be used to quantify the following analytes:
- Nitrate;
- Phosphate;
- Sulfite.
- Note: Not approved for Fluorine (F2)

Charge first two collection impingers with 15 mL 0.1 N H2SO4 each;
Charge next two collection impingers (4 & 5) with 15 mL 0.1 N NaOH each;
Charge fifth impinger with silica gel.
Filter holder must be teflon;
Separation of Analytes:
- Acid gases (hydrogen halides) are soluble and collected in the dilute sulfuric acid solution;
- Halides (chlorine and bromine) are insoluble in the acidic solution. They will pass through these impingers and be collected in the sodium hydroxide absorbing solution.
If water droplets are expected, a cyclone pre-collector should be used for separation from the sample.
- Post-sampling; The train should be purged with clean dry air to evaporate the droplets.
- This is to minimize collection of salts (e.g. sodium chloride) and/or scrubbing of acid gases onto droplets on the filter.
If high moisture content is expected, an optional pre-impinger can be inserted prior to the first two. This impinger should be charged with 50 mL of the 0.1 N H2SO4 absorbing solution.
The sodium hydroxide solution will have to be treated with sodium thiosulfate in a stoichiometric ratio to convert hypohalous acids to halides prior to analysis.

Both the H2SO4 and NaOH absorbing solutions should be shipped as a hazardous material. Please call for IATA codes if you need them.
Samples may be shipped at ambient temperatures.
Be sure to include a chain of custody for each shipping container.