Hi!
I have been running an automated SPE of 1,4-dioxane analysis for 100ml samples and have done much of the initial quality control data on 500 ml samples. I find that the Resprep EPA method 521 activated charcoal cartridges worked really well and best for low level detection, although it does take longer for the extraction process to complete due to the larger sample volume.
The 100ml sample option has worked well in my labs favor because smaller sample bottles are cheaper for purchase and we save time on the extraction process. However, when using AC-2 Sep-Pak activated carbon cartridges from Waters, we have seen a fingerprint formation of peaks of the 58 ion that makes it tough to confirm the identity of our target analyte in samples with low levels of 1,4-dioxane (<0.40 ug/L) due to coelution of the analyte 58 ion and the fingerprint peaks we see in the extraction(only seen in extracted samples). I am still in search of a solution to this issue, but it is the biggest impediment I have when performing this method.
Good luck with your analysis and if you find any solutions please share!