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Ask the Chemist Vol. 3 - 1,4-Dioxane Reporting Limits

I am going to be testing groundwater at a site that is suspected to be contaminated with 1,4-dioxane, and the cleanup standard for groundwater is 3 ug/L. However, I am looking at some laboratory reports for reference, and the limit of detection is 70 ug/L (Method 8260), which is too high to give us meaningful data for this site. Why is the reporting limit for 1,4-dioxane in water so much higher than the other volatiles on the 8260 list? Can anything be done to achieve a meaningful reporting limit?

What is 1,4-dioxane?

The compound 1,4-dioxane is a stabilizer that is often used in chlorinated solvents, paint strippers, greases and waxes. It is often found at sites impacted with chlorinated solvents. Notably, it was used as a stabilizer and corrosion inhibitor with 1,1,1-trichloroethane (TCA) and is commonly detected at sites where TCA is present. In fact, EPA recommends testing for 1,4-dioxane when TCA is a known contaminant.


1,4-dioxane is a volatile organic compound that is highly soluble and leaches readily from soil to groundwater. 
"The chemical is a cyclic either that is highly miscible in water; in fact, it mixes with water so readily that it can be found in groundwater plumes far in advance of any solvents with which it might have entered the subsurface originally."

-EPA Clu-In Technical Overview

Once dissolved in water, 1,4-dioxane favors remaining in solution; the dissolved compound has low potential to volatilize from solution into the vapor state.

How does that affect laboratory analysis?

The characteristics that make 1,4-dioxane more difficult to detect at low levels using the typical laboratory method for volatiles analysis (8260) are its high solubility and low potential to partition from the dissolved phase to vapor. Typical methods for volatiles analysis use purge and trap to concentrate the contaminant vapors from the water sample before analysis by GC/MS. The compound 1,4-dioxane does not purge from the sample as well as other volatiles, resulting in lower recovery of the compound, and a comparable higher detection limit.

To demonstrate, detection and reporting limits for most volatiles are significantly lower than 1,4-dioxane when analyzed by Method 8260.


Typical Limit of Detection (LOD)

Typical Reporting Limit or Limit of Quantitation (LOQ)

Most VOCs

0.05 to 2 µg/L or less

0.5 to 20 µg/L or less


70 µg/L

250 µg/L

How can you measure lower levels of 1,4-dioxane?

To achieve lower detection and reporting limits for 1,4-dioxane, modifications to typical EPA methods must be made. Alternative modified methods that may be used to detect 1,4-dioxane are typically based on Method 8260 or 8270.

At ECCS, to achieve the low-level reporting limits needed for your project, 1,4-dioxane is concentrated from groundwater samples using solid phase extraction (SPE) and is then analyzed by Method 8260 direct injection quantitation techniques. With the modified method, a detection limit (0.057 ug/L) and reporting limit (0.16 ug/L) far below regulatory action limits can be achieved.
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