A few years ago US EPA lowered a guideline limit to 0.3 ug/L. Some states quickly adopted this limit. Some states lowered it even further to 0.25 ug/L and others raised it a bit to 0.4 ug/L. But the question is, “What method should be used to detect 1,4 dioxane at these very low levels?”
Of course, the answer is, it depends. 1,4 dioxane is very miscible in water so it doesn’t purge very well. This means that your typical volatile analysis like EPA method 8260 is not going to work unless you employ the selective ion monitoring (SIM) technique. Still, the 8260 SIM method approach would require that the sample being tested is pretty clean. That is no other compounds present in high concentrations. Since we know 1,4 dioxane is used as chlorinated solvent stabilizer if these compounds are present in significant amounts then the 8260 method is not a good choice. Also, even if the sample is clean, the data from this method at these low levels is not very reliable due to very low recovery levels.
Another method to consider for 1,4 dioxane low level is a modified 8270 SIM method. This approach uses an isotope dilution extraction which is not affected by high concentrations of chlorinated solvents. The isotope dilution technique compensates for low percent recoveries and generates very low reporting limits and more reliable data than the 8260 approach. Also available is the EPA 522 method designed for drinking water and uses a solid phase extraction and has similar low reporting limits and more reliable data than the 8260 approach. This technique can be affected by a turbid sample.
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