1,4-Dioxane

1,4-Dioxane is highly soluble in water, does not bind to soils, and readily leaches to groundwater. The compound is known to co-occur at sites where chlorinated solvents have been used (Anderson et al. 2012, Adamson et al. 2014). Given 1,4-Dioxane's mobility, a key issue in characterizing these sites is establishing the extent of migration within groundwater.

Sample Location. 1,4-Dioxane has the potential to migrate considerably farther in groundwater than solvents such as TCA [1,1,1-trichloroethane] or its breakdown products due to the compound's complete miscibility and the absence of conditions that promote its biodegradation, which is a consideration for where to take samples during assessment work (MADEP 2015). However, a study reported by Adamson et al. (2014) demonstrated that many 1,4-Dioxane plumes are currently similar or shorter in length than those of co-occurring chlorinated solvents. This pattern was based on empirical data and likely was influenced by the history of solvent usage at different sites (e.g., the first solvents used and released at a site may not have contained 1,4-Dioxane).

Sample Collection & Equipment Decontamination. Materials used in environmental sampling can be a source of 1,4-Dioxane contamination. 1,4-Dioxane also might be present in detergents used to decontaminate environmental sampling equipment. Use of those detergents, therefore, could potentially affect analytical results if sampling equipment is insufficiently rinsed during decontamination. When sampling for 1,4-Dioxane, collection of additional or more frequent field/equipment blanks is recommended prior to and during sampling to ensure no residual 1,4-Dioxane remains on the sampling equipment (MADEP 2015).

Other 1,4-Dioxane Sources. Plume delineation should be sufficient to locate the source of 1,4-Dioxane contamination, but multiple sources of contamination not associated with solvent releases may contribute to the presence of 1,4-Dioxane. For example, products such as shampoos and detergents have been known to contain 1,4-Dioxane, which can enter the environment through wastewater treatment plants and septic systems (MADEP 2015). Mohr (2017) observed that "Where septic, recycled water, or sewer line exfiltration play a significant role in groundwater recharge, 1,4-Dioxane may be present from wastewater/surfactant sources. Surface water sources are more likely to include 1,4-Dioxane from upstream wastewater effluent." Other sources could include laboratories, landfills, military sites, and airports (where de-icing fluids were used).

Plume Delineation. In an evaluation of >2,000 sites in California where groundwater has been affected by chlorinated solvents and/or 1,4-Dioxane, Adamson et al. (2014) Curry et al. (2016) and Davis et al. (2015) present approaches for using on-site laboratories to screen soil and water samples to provide high sample density for delineating 1,4-Dioxane plumes. One approach uses SW-846 Method 8260 with solid-phase micro extraction (SPME) to process 50 samples a day (limit of detection [LOD] for water: 2-20 µg/L); the other approach uses Method 8265, Direct Sampling Ion Trap Mass Spectrometry (DSITMS)/SPME to process 60-80 samples per day (LOD for water: 2-5 µg/L).

Assessment of Biodegradation Potential. Although 1,4-Dioxane has been considered resistant to naturally occurring biodegradation processes, there is evidence that naturally occurring biodegradation can take place at 1,4-Dioxane sites under appropriate conditions (Adamson et al. 2015). If naturally occurring biodegradation is suspected at a site, testing for biomarkers for 1,4-Dioxane degradation and other lines of evidence for attenuation during the remedial investigation is recommended.

Richards (2016) and Gedalanga et al. (2016) present several approaches for obtaining lines of evidence to evaluate the intrinsic biodegradation of 1,4-Dioxane in a groundwater plume. These include establishing spatial distributions, geochemical biodegradation indicator parameters, fate and transport modeling, compound-specific isotope analyses, and biomarker analyses (e.g., using dioxane monooxygenase [DXMO] and aldehyde dehydrogenase [ALDH]).

Alvarez et al. (2014), Gedalanga et al. (2014), and Li et al. (2014) provide discussions on 1,4-Dioxane biomarkers and the development of probes to detect them. The abundance of these biomarkers has been positively correlated with 1,4-Dioxane biodegradation rates (Li et al. 2014, da Silva et al. 2018).

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Additional Resources

Advisory: Active Soil Gas Investigations
California Environmental Protection Agency, Department of Toxic Substances Control, Los Angeles Regional Water Quality Control Board, and San Francisco Regional Water Quality Control Board. 97 pp, 2015

This updated Advisory contains technical information, knowledge, experience and best practices regarding soil gas sampling. The list of target compounds includes 1,4-Dioxane.

Breakthrough in 2D-CSIA Technology for 1,4-Dioxane
Wang, Y.
Remediation Journal 27(1):61-70(2016) [Abstract]

A dual isotope technology based on compound-specific stable isotope analysis of carbon and hydrogen (2D-CSIA) was recently developed to help identify sources and monitor in situ degradation of 1,4-Dioxane in groundwater, reported down to ~1 µg/L for carbon and ~10-20 µg/L for hydrogen using solid-phase extraction based on EPA Method 522. Application of the technology is highlighted in a case study at a 1,4-Dioxane-contaminated site.

Extending the Applicability of Compound-Specific Isotope Analysis to Low Concentrations of 1,4-Dioxane
Bennett, P.
SERDP Project ER-2535, 53 pp, 2017

The project objective was to develop a reliable method to perform CSIA on low aqueous concentrations (1 µg/L) of 1,4-Dioxane in groundwater and then apply it to investigate 1,4-Dioxane biodegradation. It was determined that 0.5 grams of a synthetic carbonaceous sorbent, when added to a 40 mL vial containing aqueous 1,4-Dioxane in the 10 to 100 µg/L range, could adsorb > 99% of the 1,4-Dioxane from solution. The 1,4-Dioxane was recovered from the dried solid sorbent by thermal desorption into a gas chromatograph with isotope ratio mass spectrometry. The method was applied successfully to samples at concentrations in the 1 µg/L range. It is anticipated that the CSIA method will be applied to demonstrate the biodegradation of 1,4-Dioxane in the 1-100 µg/L range.

Fact Sheet: Guidance on Sampling and Analysis for 1,4-Dioxane at Disposal Sites Regulated under the Massachusetts Contingency Plan
Massachusetts Department of Environmental Protection, 8 pp, 2015

This fact sheet provides guidance on the sampling and analysis of 1,4-Dioxane in groundwater at disposal sites regulated under the Massachusetts Contingency Plan, focusing on 1,4-Dioxane in groundwater. It also summarizes 1,4-Dioxane physical and chemical properties, environmental health impacts, state and federal standards and guidelines, and appropriate analytical methods.

Groundwater Sampling for 1,4-Dioxane, PFAS, and Metals Using the Dualmembrane Passive Diffusion Bag Sampler
Andrew, A. and B. Varhol. | 29th Annual David S. Snipes/Clemson Hydrogeology Symposium, 21 October, Clemson, SC, 17 minutes, 2021

EPA Method 8265 is based on solid-phase microextraction (SPME) followed by mass spectrometric analysis using the direct sampling ion trap mass spectrometer (DSITMS). Method 8265 has been demonstrated to provide quantitative analysis of 1,4-Dioxane to limits of detection of 2-5µg/L for groundwater and 10-15µg/kg for soil samples. This presentation illustrates how the method was used in an on-site laboratory to delineate 1,4-Dioxane and VOC plumes at several sites.

High-Resolution 1,4-Dioxane Source Area Characterization
Curry, P.J. and J. Quinnan.
Emerging Contaminants Summit, 25 slides, 2016

This presentation discussed "Smart" site characterization and the use of mobile on-site laboratories for rapid 1,4-Dioxane investigation and delineation of a 1,4-Dioxane plume. Contractors used Method 8260 (solid-phase micro-extraction, or SPME) to process 50 samples/d (water and/or soil) and Method 8265 (direct-sampling ion-trap mass spectrometry, or DSITMS/SPME) to process 60-80 samples/d, and then compared the results. The sampling and analysis capability allowed for high-density sampling and facilitated the ability to use flux-based source evaluation.

High Resolution Site Characterization of 1,4-Dioxane Sites Using a New On-Site, Real-Time Analysis
Davis, W.M., C.P. Antworth, and C.A. Horrell.
IPEC 2015: International Petroleum Environmental Conference Denver, CO. 22 slides, 2015

EPA Method 8265 is based on solid-phase microextraction (SPME) followed by mass spectrometric analysis using the direct sampling ion trap mass spectrometer (DSITMS). Method 8265 has been demonstrated to provide quantitative analysis of 1,4-Dioxane to limits of detection of 2-5µg/L for groundwater and 10-15µg/kg for soil samples. This presentation illustrates how the method was used in an on-site laboratory to delineate 1,4-Dioxane and VOC plumes at several sites.

Mass Flux Toolkit to Evaluate Groundwater Impacts, Attenuation, and Remediation Alternatives
Environmental Security Technology Certification Program (ESTCP), 2006

To help site managers and site consultants estimate mass flux and understand the uncertainty in those estimates, ESTCP funded the development of a computerized Mass Flux Toolkit, free software that gives site personnel the capability to compare different mass flux approaches, calculate mass flux from transect data, and apply mass flux to manage groundwater plumes. The toolkit spreadsheet and associated documentation are available on the ESTCP contractor's website in a zipped file.

A Multiple Lines of Evidence Framework to Evaluate Intrinsic Biodegradation of 1,4-Dioxane
Gedalanga, P., A. Madison, Y.R. Miao, T. Richards, J. Hatton, W.H. DiGuiseppi, J. Wilson, and S. Mahendra.
Remediation Journal 27(1):93-114(2016) [Abstract]

A comprehensive multiple lines of evidence (MLOE) approach provided significant evidence of natural degradation of 1,4-Dioxane comingled with tetrahydrofuran (THF) within a large, diffuse plume. Molecular analyses demonstrated that microorganisms capable of both metabolic and cometabolic degradation of 1,4-Dioxane were present throughout the groundwater plume. Evidence also suggests that THF-driven cometabolic biodegradation as well as catabolic 1,4-Dioxane biodegradation were active at this site.

Results Report for the Demonstration of No-Purge Groundwater Sampling Devices at Former McClellan Air Force Base, CA
U.S. Army Corps of Engineers Omaha District, Air Force Center for Environmental Excellence, and Air Force Real Property Agency. 79 pp, 2005

Analyses of VOCs, metals, anions, and 1,4-Dioxane concentrations in samples from four diffusion and two grab-type no-purge samplers were compared to those from conventional low-flow and three-well-volume purge samples. The HydraSleeve®, Snap Sampler™, PsMS, and RCS appeared to produce results that were similar to or higher than the results obtained using conventional methods (i.e., low-flow and three-volume purge), suggesting that they could be substituted for the conventional methods in at least some situations. Although similar to low-flow results, results obtained using the rigid porous polyethylene sampler tended to be biased low relative to three-volume results; therefore, this sampler was not endorsed for use with 1,4-Dioxane.

Sampling and Analysis: 1,4-Dioxane
Interstate Technology and Regulatory Council (ITRC), 6 pp, 2020

The Interstate Technology and Regulatory Council (ITRC) has developed a series of six fact sheets to summarize the latest science and emerging technologies regarding 1,4-Dioxane. The purpose of this fact sheet is to: describe potential concerns when sampling for 1,4-Dioxane; identify the common analytical methods available for 1,4-Dioxane in different matrices, including water, solids, and air; and highlight the benefits and limitations of the available analytical methods.

Smart Characterization: An Integrated Approach for Evaluating a Complex 1,4-Dioxane Site
Curry, P., N. Welty, J. Wright, D. Favero, and J. Quinnan.
Remediation Journal 27(1):29-45(2016) [Abstract]

Smart characterization concepts discussed in this article include high-resolution site characterization methods to find the contaminant mass flux by integrating relative permeability mapping, classical hydrostratigraphy interpretation, and high-density groundwater and saturated soil sampling. For 1,4-Dioxane, this article provides a phase calculation showing the relative amounts of 1,4-Dioxane in water, soil, and gas. The recommended Smart approach involves the use of specialized high-capacity mobile laboratories.

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Analytical Methods

The intent in this section is not to provide an exhaustive list of analytical methods, but to identify well-established, standard methods, particularly those used for environmental samples. Commercial laboratories will often offer variations on these methods to improve sensitivity for 1,4-Dioxane. Performance and sensitivity may vary by laboratory and sample matrix type; prospective data users are encouraged to contact individual laboratories to ascertain whether their project needs can be met.

Note that many 1,4-Dioxane plumes at contaminated sites can be considered relatively dilute, with maximum concentrations in groundwater generally well below 1 mg/L (Adamson et al. 2014); therefore, it is important to select analytical methods that are appropriate for quantifying low levels of 1,4-Dioxane.

Commercial laboratories commonly analyze for 1,4-Dioxane in water by three methods: EPA Method 522 for drinking water, and EPA SW-846 methods 8260D and 8270E for water and soil.

In 2008 EPA released Method 522, "Determination of 1,4-Dioxane in Drinking Water by Solid Phase Extraction (SPE) and Gas Chromatography/Mass Spectrometry (GC/MS) with Selected Ion Monitoring (SIM)." This method was developed for and is used for regulatory compliance testing of finished drinking water, and it includes performance data showing excellent recovery in the mid ppt (ng/L) concentration range.

1,4-Dioxane can be analyzed like other volatile organic chemicals (VOCs) by ambient temperature purge-and-trap (5030C) and full scan GC/MS (8260D). However, this technique typically is capable only of achieving a lower limit of quantitation (LLOQ) in the high parts-per-billion (ppb; µg/L) range for aqueous samples, which is insufficient for project applications requiring low- to sub-µg/L measurements (MADEP 2015). Poor sensitivity relative to other VOCs analyzed by this technique is a result of poor purging efficiency due to its water solubility (Neslund 2016). Heating samples and standards to a uniform temperature during purging and adding a matrix modifier (typically an inorganic salt such as sodium sulfate) to standards and samples improves purging efficiency (Mohr 2001). These modifications can improve overall measurement sensitivity by 1-2 orders of magnitude and reduce run-to-run variability. Operation of the MS in selected ion monitoring mode can also improve sensitivity by 1-2 orders of magnitude compared to scanning mode. These modifications may be sufficient to meet project requirements in the high parts-per-trillion (ppt, ng/L) range (MADEP 2015, Neslund 2016). Other VOC preparative techniques, such as azeotropic distillation (SW-846 method 5031) and vacuum distillation (SW-846 method 5032), and determinative methods, such as gas chromatography with flame ionization detection (SW-846 method 8015), are also referenced in the table below.

Sensitive determination of 1,4-Dioxane in water also can be accomplished using separatory-funnel or continuous liquid-liquid extraction (SW-846 methods 3510C, 3520A) and analysis by capillary column GC/MS (SW-846 method 8270E) in SIM mode (MADEP 2015, CAS 2010, Test America 2017). This GC/MS method is typically optimized for 1,4-Dioxane as a single analyte. Recovery is not as high (typically ≤ 50%) and tends to be more variable than by the SPE procedure in Method 522, but the measured concentrations can also be recovery-corrected using a mass-labeled 1,4-Dioxane-d8 surrogate, providing high-confidence concentration estimates. If other contaminants of concern are present, a second full run scan may be needed.

The table below summarizes these methods.

MATRIX	METHOD	INSTRUMENTATION	DETECTION LIMIT
Soil, Water	EPA SW-846, Method 5031/ 8015D	GC/FID	12-16 µg/L (8015D Table 1)
Water	EPA Method 1624C (Note: compound listed as a method analyte)	P&T GC/MS (ID or internal standard)	50 µg/L (1624C Table 3); 1 µg/L (heated purge + salt in SIM mode; Mohr 2001)
Soil, Water	EPA SW-846, Method 5030C or 5035A /8260D	P&T GC/MS	36.9-250 µg/L or µg/kg (limit of quantitation for ambient temp purge in scan mode; Neslund 2016); 2 µg/L (detection limit from heated purge + salt addition in scan mode; Mohr 2001)*
Soil, Water, Tissue	EPA SW-846, Method 5032/8260D or Method 8261	VD/GC/MS labeled ID	4-20 µg/L or µg/kg (Mohr 2010)*
Soil, Water	EPA SW-846, Method 3510C or 3520A (waters), Method 3540, 3545, 3546, 3550 (solids) /Method 8270E	LLE, GC/MS	5 µg/L or 330 µg/kg (Separatory funnel extraction for waters; ultrasonic or microwave extraction for soils; scan mode; Neslund 2016)*
Soil, Water	EPA SW-846, Method 8270E SIM ID	LLE, GC/MS-SIM	0.2-0.4 µg/L (Test America); 0.2 µg/L, 1.7 µg/kg (Neslund 2016)
Air	EPA Method TO-15	GC/MS	<1 ppbv (LeBouf et al. 2010)
Air	NIOSH 1602	GC/FID	0.01 mg/m3
Water (Drinking)	EPA Method 522	SPE, GC/MS-SIM	0.04 -0.05 µg/L

Abbreviations: FID — flame ionization detector; GC — gas chromatography; ID — isotope dilution; LLE — liquid-liquid extraction; MS — mass spectrometry; P&T — Purge and Trap; SIM — selected ion monitoring; SPE — solid-phase extraction; VD — vacuum distillation.
* Selected ion monitoring (SIM) can increase the sensitivity of GC/MS analysis by 1-2 orders of magnitude, but some of the spectral information is sacrificed.

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Additional Resources

Challenges and Options for the Analysis of 1,4-Dioxane
Neslund, C.
NEMC 2016: National Environmental Monitoring Conference, 8-12 August, Orange County, CA, 21 slides, 2016 [Abstract]

SW-846 methods 8260 and 8270 can be modified to meet or exceed a health-based advisory level of 3 µg/L. This presentation discusses the details of using 8260 versus 8260 SIM and 8270 versus 8270 SIM as well as the advantages and pitfalls of each.

Determination of 1,4-Dioxane in the Cape Fear River Watershed by Heated Purge-and-Trap Preconcentration and Gas Chromatography-Mass Spectrometry
Sun, M., C. Lopez-Velandia, and D.R.U. Knappe.
Environmental Science & Technology 50(5):2246-2254(2016) [Abstract]

A rapid and sensitive analytical method capable of quantifying 1,4-Dioxane over a wide concentration range in a broad spectrum of aqueous matrices was developed to support dioxane occurrence investigations, source identification, and exposure assessment. Based on heated purge-and-trap pre-concentration and GC-MS with selected-ion storage, the fully automated method has a reporting limit of 0.15 µg/L and allows 1,3-dioxane to be distinguished from 1,4-Dioxane.

Environmental Laboratory Advisory Committee (ELAC) Meeting Minutes: January 14, 2016
New Jersey Department of Environmental Protection, 3 pp, 2016

Issues in the use of 8260 SIM versus 8270 SIM were briefly discussed (page 2).

EPA Contract Laboratory Program Statement of Work for Organic Superfund Methods: Multi-Media, Multi-Concentration
U.S. Environmental Protection Agency, SOM02.4 Exhibits A-C, D, and E-H, 2016

See Exhibit D for CLP-specific information on holding times, preservation, and calibration for 1,4-Dioxane in water by EPA 8270D. Note that the contract-required detection limit for 1,4-Dioxane in water is 2.0 µg/L (page C-8), which may be too high for some applications.

Measurement of 1,4-Dioxane in Surface Water by Headspace GC-MS
Hong, S.-W., J.-B. Lee, S.-H. Lee, H.-S. Lim, and H.-S. Shin.
Analytical Science & Technology 27(1):22-26(2014)

1,4-Dioxane was measured in surface water with headspace GC-MS detection. A 5 mL water sample was placed in a 10 mL headspace vial and saturated with NaCl; the solution was spiked with 1,4-Dioxane-d8 as an internal standard and then sealed with a cap. In water samples collected from the Gum River in June and September 2012, 1,4-Dioxane was detected in the concentration range of 0.49-43.0 µg/L (mean 2.0 µg/L) in about 30% of the samples.

Method 522 Determination of 1,4-Dioxane In Drinking Water by Solid Phase Extraction (SPE) and Gas Chromatography/ Mass Spectrometry (GC/MS) with Selected Ion Monitoring (SIM)
Munch, J.W. and P.E. Grimmett.
EPA 600-R-08-101, 41 pp, 2008

Method 1624, Revision B: Volatile Organic Compounds by Isotope Dilution GC/MS - Appendix A to Part 136
U.S. EPA, Office of Water, 32 pp, Promulgated 1984

The minimum detection limit for dioxane is identified as 10 µg/L.

Optimization of 1,4-Dioxane and Ethanol Detection Using USEPA Method 8260
Jurek, A.
2017 NEMC: National Environmental Monitoring Conference, 7-11 August, Washington, DC. Poster, 2017 [Abstract]

Due to the miscibility of 1,4-Dioxane and ethanol and their propensity to stick to the sparge vessel of the purge and trap during analysis by Method 8260, purge and trap sampling needs to be optimized. This poster investigates seven variations of purge and trap sampling and compares linearity, method detection limits, precision and accuracy, and carryover of several purge and trap sampling parameters.

The Problem with 1,4-Dioxane
Heigel, C., M. Wilken, and C. Ballek.
2016 NEMC: National Environmental Monitoring Conference, 8-12 August, Orange County, CA. 21 Slides, 2016 [Abstract]

Summaries of analytical methods used for dioxane are presented along with methods for sample preparation and results of proficiency testing of the methods in multiple laboratories.

Rapid Analysis of 1,4-Dioxane in Groundwater by Frozen Micro-Extraction with Gas Chromatography/Mass Spectrometry
Li, M., P. Conlon, S. Fiorenza, R.J. Vitale, and P.J.J. Alvarez.
Ground Water Monitoring & Remediation 31(4):70-76(2011)

Innovative micro-extraction of aqueous samples coupled with GC-MS in selected ion-monitoring mode analyzes for 1,4-Dioxane selectively with low ppb detection sensitivity. Freezing the aqueous sample along with the extraction solvent enhances extraction efficiency, minimizes physical interferences, and improves sensitivity, achieving a limit of detection for 1,4-Dioxane to ~1.6 µg/L in a relatively small sample volume (200 µL).

Standard Operating Procedure for Measurement of Purgeable 1,4-Dioxane in Water by GC/MS
U.S. EPA, Region 1, Office of Environmental Measurement and Evaluation.
Standard Operating Procedure (SOP) VOADIOX3, 24 pp, 2004

Technical Fact Sheet — 1,4-Dioxane
U.S. EPA, Federal Facilities Restoration and Reuse Office

This fact sheet provides a summary of information on 1,4-Dioxane, including physical and chemical properties; environmental and health impacts; existing federal and state guidelines; detection and treatment methods; and additional sources of information.

Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods, 3rd Edition
U.S. Environmental Protection Agency, SW-846.

Note: Methods 5030 (Purge-and-Trap for Aqueous Samples), 5032 (Volatile Organic Compounds by Vacuum Distillation), and 5035 (Closed-System Purge-and-Trap and Extraction for Volatile Organics in Soil and Waste Samples) carry a warning that they have poor recovery for soluble chemicals.

Method 5030B: Purge-and-Trap for Aqueous Samples

Method 5031: Volatile, Nonpurgeable, Water-Soluble Compounds by Azeotropic Distillation

Method 5032: Volatile Organic Compounds by Vacuum Distillation

Method 5035: Closed-System Purge-and-Trap and Extraction for Volatile Organics in Soil and Waste Samples

Method 8015C: Nonhalogenated Organics Using GC/FID

Method 8261: Volatile Organic Compounds by Vacuum Distillation in Combination with Gas Chromatography/Mass Spectrometry (VD/GC/MS)

Method 8270C: Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS)

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Validation Methods

EPA and independent laboratories validated the following methods, which are recommended for use as the most up-to-date methods available. However, these methods have not been formally incorporated into the SW-846 Compendium through the public comment process.

Validated Test Method 5030C: Purge-and-Trap for Aqueous Samples

Validated Test Method 5035A: Closed-System Purge-and-Trap and Extraction for Volatile Organics in Soil and Waste Samples

Method 8265: Volatile Organic Compounds in Water, Soil, Soil Gas, and Air by Direct Sampling Ion Trap Mass Spectrometry (DSITMS)

Validated Test Method 8260D: Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS)
This method includes a discussion of using SIM.

Validated Test Method 8270E: Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS)
This method includes a discussion of using SIM.

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