The primary association of 1,4-dioxane with environmental releases was its use as a stabilizer and a chemical inhibitor with chlorinated solvents, particularly 1,1,1-trichloroethane. While this was the most common source, 1,4-dioxane was used for a wide variety of other industrial processes as well. In addition, it should be noted that 1,4-dioxane is present in numerous consumer and commercial products that can enter the environment via septic systems and/or landfills.
Practitioners are reminded of the additional considerations that must be taken into account if 1,4-dioxane is considered a potential contaminant of concern. 1,4-dioxane’s physical properties make it especially challenging to analyze for (and remediate) in groundwater sample media. This is especially true for groundwater associated with regulatory criteria of less than 1 ug/L.
From an analytical perspective, 1,4-dioxane can be prepared for analysis as a volatile organic compound (VOC) or as a semivolatile organic compound (SVOC). As discussed, due to its physical properties, it cannot be easily purged as a VOC. In addition, due to its use as a chemical stabilizer for some chlorinated solvents, the presence of 1,4-dioxane is often suspected at these sites. For sites with high chlorinated VOC groundwater concentrations, these high CVOC analyte concentrations require samples to be diluted, often substantially, prior to analysis. These dilutions result in very high detection limits for 1,4-dioxane given that the sensitivity by Method 8260 is marginal even without any dilution. It should be noted that dilutions would still be required for high CVOC concentrations present in a sample, regardless if the analysis is being conducted specifically for 1,4-dioxane only. For these reasons, Alpha Analytical does not recommend utilizing a VOC approach, such as Method 8260, when the required detection limit is less than 1 ug/L.
Alpha Analytical offers two analytical method options for the analysis of 1,4-dioxane when the required reporting limit is less than 1 ug/L. The choice of which method to use depends on your project application and any associated regulatory requirements. Alpha Analytical holds both DOD ELAP and NELAC certification for 1,4-dioxane analysis by either Method 8270M or Method 522. An overview of both methods follows. We would be happy to discuss the relative merits of each approach with you if you need additional information.
Modified Method 8270 SIM w/Isotope Dilution
Superior chromatographic performance and greater sensitivity is achieved when Method 8270 is modified for 1,4-dioxane specifically with the mass spectrometer operated in the selected ion mode incorporating the isotope-dilution technique for greater analytical certainty. Isotope dilution techniques incorporate a deuterated form of the target analyte (1,4-dioxane-d8), which is spiked into every sample to act as a target-specific internal standard that is incorporated into the sample quantitation to normalize extraction recoveries. This approach also has the advantage of having no interference from chlorinated solvents as samples can be analyzed from sites with high concentrations of VOCs present with no dilutions required.
EPA Method 522
Method 522 has been promulgated by EPA for the analysis of 1,4-dioxane in drinking water. This procedure also utilizes GC/MS SIM (no isotope dilution) but it utilizes a different preparative procedure. Aqueous samples are extracted by a solid phase extraction (SPE) technique. It should be noted that this methodology was developed specifically for the drinking water matrix with very specific and prescriptive sample preservation requirements. These requirements can be modified for groundwater samples; however, this method so modified cannot be used to analyze public water system samples. Groundwater with varying dissolved / suspended solids content may also impact the performance of the Method 522 SPE procedure. For public water supply samples, Method 522 must be used as written for 1,4-dioxane samples. For drinking water samples from a private water supply, either the 8270 SIM isotope dilution method or Method 522 can be used, as long as all associated regulatory considerations are met.
There are a lot of additional considerations required if low level 1,4-dioxane analysis is required. Make sure to address any questions you may have with the laboratory upfront, as sampling containers and preservation will vary between the methods. Practitioners are also advised to incorporate field blanks (make sure they are 1,4-dioxane free) into their sampling programs at a conservative frequency whenever low-level analysis is required. Lastly, make sure you recognize that any detergents used for decontamination of sampling equipment could potentially be a source of 1,4-dioxane.