Chemical Measurement Division


EPA Method 26a

Hydrogen Halide & Halogen-Isokinetic

Method Overview

  • • Isokinetic train.
  • • Use cyclone for supersaturated sources.
  • • Filter separates particulate halides from gaseous halides.
  • • As with Method 26, typically only the gaseous halides are analyzed.
  • • Analysis by HPLC/IC.

Target Compounds

  • • Hydrochloric acid
  • • Hydrogen fluoride
  • • Hydrogen bromide
  • • Chlorine (Cl2)
  • • Bromine (Br2)
  • • Also: Nitrate, Sulfite, Phosphate
  • • Not approved for fluorine (F2)

Method Summary

  • • Charge 1st 2 impingers with 15 mL 0.1N H2SO4. Charge 3rd and 4th impingers with 0.1N NaOH. Charge 5th impinger with silica gel.
  • • Filter holder must be Teflon.
  • • Acid gases, HCl, HF, and HBr are soluble in H2SO4 and collected in the first few impingers. Cl2 and Br2 are not soluble in the acid impingers and pass through to be collected in the basic impingers (NaOH).
  • • If water droplets are expected, use M26A.
  • • If high moisture is expected, an optional 1st impinger may be added with a short stem; place 5 mL of 0.1N H2SO4 in the optional impinger to acidify the contents.
  • • When Cl2 or Br2 are analytes, add sodium thiosulfate to the NaOH reagent after the run, which will convert hypohalous species back to Cl- or Br- for proper analytical quanitation.

Quality Assurance

  • • Water blank.
  • • Reagent blank.
  • • HCl audits are available to agencies.
  • • Enthalpy will provide separate analytical curves for the acid and base fractions, with each curve generated in the same matrix as the sample. 4 standards are analyzed in duplicate before and after the analysis.

Shipping Tips

  • • H2SO4 and NaOH are hazardous and should be shipped as Hazardous Goods. (Call us for the IATA codes as required.)
  • • Reagents need not be shipped cold.
  • • Important - include a complete Chain of Custody form for EACH shipping container. (See our downloads section for a COC form.)

Enthalpy Experience

  • • Enthalpy has analyzed M26 and M26A fractions for ~6 years, and during that time we have never failed an EPA audit for M26.
  • • A more extensive compound list is available for engineering tests, albeit not approved for compliance.
  • • Sulfate is a problem for the analysis and can sometimes, though not always, be removed by addition of BaCl2.
  • • Enthalpy operates an Alltech suppression system that increases the sensitivity of the analysis. When sulfate is a problem, the increased instrument sensitivity allows us to dilute the samples to minimize sulfate while maintaining acceptable detection limits.