1,4-Dioxane Analysis by GCMS

Introduction

1,4-Dioxane has always been of concern as an environmental hazard. Currently, EPA 8260 leads to detection limits in the range of 100 ug/L due the water solubility of dioxane.

1,4-dioxane

Now that the California EPA Preliminary Endangerment Assessment (PEA) requires a 2.5 ug/L practical quantitation limit, a new or modified method is needed to satisfy these requirements. Modifications to both purge and trap GCMS method 8260 and to the extraction GCMS method 8270 were evaluated. While both techniques are capable of reaching detection limits of 1-2 ug/L, the extraction method was found to be more reliable. For a quotation...

1,4-Dioxane by Modified EPA 8260: Purge and Trap GCMS

A modification to EPA volatile organics analysis was needed for low level 1,4-dioxane analysis. In the past, one of the main drawbacks with this method has been high detection limits mainly due to the poor purging efficiency of 1,4-dioxane from the water matrix. A number of modifications to Method 8260 were required in order to achieve the PQL of 2.5 ug/L. To eliminate as much of the water from the system as possible, a moisture control module was utilized. A salt, in this case

sodium sulfate, was added to the sample to enhance the purge efficiency of 1,4-dioxane. Also a heated sparge was used to further improve the sensitivity of the method. These modifications combined with optimized scan parameters on the GCMS system greatly improved the sensitivity. Using normal Method 8260 procedures, a detection limit of approximately 100 ug/L was common. With these modifications one can reasonably achieve a detection limit of 2.0 ug/L. However, during repeated attempts to use this procedure, problems were encountered, and the method does not appear to be reliable.

1,4-Dioxane by Modified EPA 8270: Isotope Dilution, Extraction and GCMS

In the new method 1,4-dioxane-d₈ is used as an isotope dilution standard added to the water prior to extraction. The sample is then extracted overnight using continuous liquid-liquid extraction with methylene chloride. The extract is then concentrated to 1 mL and analyzed by GCMS. Even though the extraction efficiency using continuous liquid-liquid extraction is approximately 60%, the isotope dilution analysis minimizes the error caused during extraction and analysis. Percent recoveries of 20 ug/L spikes are normally in the range of 90-105% when corrected using the isotope dilution technique.

Click on 1,4-dioxane for a chromatogram of 1,4-dioxane and 1,4-dioxane-d₈.

In an MDL study, seven replicate water samples spiked at 2 ug/L gave an RSD of only 3.7%. This is an MDL or 0.23 ug/L. We have adopted a reporting limit of 0.5 ug/L.

While none of the current environmental performance studies have samples for 1,4-dioxane, one of our clients had one made by ERA and sent it blind to 4 labs. We analyzed the sample on a RUSH basis (9/21/05) and passed. The certified value was 203 ug/L, and we reported 220. Acceptance criteria were 142-264 ug/L.

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1,4-dioxane analysis, GCMS, EPA Method 8260 and 8270, isotope dilution

Introduction

1,4-Dioxane by Modified EPA 8260: Purge and Trap GCMS

1,4-Dioxane by Modified EPA 8270: Isotope Dilution, Extraction and GCMS