You could take a look at this:
http://www.portablefuelsystems.com/AlcoholSeparator.htm
The guy behind it does post on these forums. Out of the Phoenix, AZ area.
There's another thread on one of the forums on here that went back and forth on this device and other processes. The conclusion I came away with is the device here does remove alcohol, but the resulting fuel does not meet a spec. So I guess in this case, it had better be for Experimental use only. Though at ~$2500 for the unit, you had better be burning a lot of auto gas, and getting your tax rebates from the state (for not using the fuel on-road) to make up the cost...

For my economics, say the delta 100LL to autogas price (including tax rebate) is $2.50/gallon based on this week's prices in my area. That's 1000 gallons burned before the investment breaks even. Just checking my fuel log, I've burned 527 gallons in 3 1/2 years of operation. So that would be between 6 and 7 years for it to pay off for me, not including the added inconvenience of hauling the unit to the auto gas station and back for refills. If you're running more hours and/or a higher burn rate aircraft, it could pay off a lot quicker.