Method 0051/9057

Midget Impinger HCl/Cl2 Emission Sampling and Analysis

This method describes the collection of hydrogen chloride (HCl) and chlorine (Cl2) in stack gas emission samples from hazardous waste incinerators and municipal waste combustors. The collected samples are analyzed using Method 9057. This method is designed to collect HCl/Cl2 in their gaseous forms. Use of this method is limited to the sampling of relatively dry, particulate-free gas streams. Sources, such as those controlled by wet scrubbers that emit acid particulate matter (e.g., HCl dissolved in water droplets), must be sampled using an isokinetic HCl/Cl2 sampling train (see Method 0050).

This method has potential for collection of all halogens and halogen acids, but has not been fully evaluated for that use. For analytical determination of additional halides, Method 9056 is used rather than Method 9057. This method is similar to EPA Methods 26 and 26A.

Samples are collected  using a heated probe, Teflon mat filter and a series of midget impingers. The 1st impinger (also called the Knockout iminger) is left empty,  2nd and 3rd impingers are filled with 15mL 0.05M H2SO4 solution.  The 4th and 5th impingers are filled with 15mL of 0.1M NaOH.  The impingers are followed by a drying tube.  It is important to keep the pH of the basic impingers strongly basic throughout the sampling and it is recommended to monitor this throughout the sampling period.  If the source is highly acidic, a stronger base, more of the NaOH solution, or a changout of the impinger during the run can be performed.

After collection, the train can be weighed if a moisture determination is needed.  The contents of the Knockout impinger and two H2SO4 impingers are combined into one container along with the water rinses of the impingers.  The contents of the two NaOH impingers are combined into one container along with the water rinses of the impingers.  Each fraction of the train is analyzed separately.  Typically, the halogen acids (HCl, HBr, HF) are determined from the H2SO4 impingers and the halogens (Br2, Cl2) from the NaOH impingers.


Per Method 9057, each sample is analyzed in duplicate.

(EPA SW-846)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   30 days from sampling to analysis
Preservatives:   2mL of sodium thiosulfate to the NaOH impinger contents
Required Preps:   Teflon mat filter
Collection Method:   Midget impinger train per SW-846 0051 procedures.
Analytical Methodology:   Ion chromatography by SW-846 9057
Documentation:   0051

Analyte List*

Analyte Formula CAS Number Detection Limit
Hydrogen chloride

* 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.