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Dense Nonaqueous Phase Liquids (DNAPLs)

Detection and Site Characterization

Halogenated Alkanes

Methylene Chloride

Methylene Chloride (MC) is a volatile halogenated organic and as such is subject to most standard characterization and analytical techniques used on this class of chemicals. Methods such as vertical profiling, dyes, and standard GC/MS are discussed in the main section for DNAPLs detection and site characterization.

Diffusion Samplers

MC-contaminated groundwater can be sampled by Diffusion Samplers (ITRC 2004).

Laboratory Methods

Analysis of MC can be performed using standard analyses such as SW-846 methods 8021b, 8260b, and 8260c.

Field Screening Methods

Draeger makes a detection tube for methylene chloride. The detection range is 20 to 200 ppm. GasTec also makes a detector tube for methylene chloride. There are two products with detection limits of 10 to 150 ppm and 20 to 500 ppm.

MC should be detectable using headspace analysis with a field GC. Standards should be run to verify detection limit requirements. If the GC uses a photoionization detector (PID) instead of an electron capture detector (ECD) the lamp must be 11.7 eV as the standard 10.6 eV lamp will not ionize MC (ionization energy of 11.35 eV (EPA 1994)). Note that this limitation would also be true for an organic vapor analyzer using a PID.

References

Standard Operating Procedure# 2114: Photoionization Detector HNU
U.S. EPA, Emergency Response Team, 16 pp, 1994

This document contains an extensive list of chemicals with their photoionization potentials.

Technical and Regulatory Guidance for Using Polyethylene Diffusion Bag Samplers to Monitor Volatile Organic Compounds in Groundwater
Interstate Technology & Regulatory Council (ITRC). DSP-3, 78 pp, 2004