All solutions were prepared with deionized water (Millipore
Direct-Q3) with a resistivity no less than 18 M-cm. All reagents
were of analytical grade and used without further purification.
Sodium hydroxide was obtained from Dinâmica (Diadema, Brazil)
and ethanol and methanol from Synth (Diadema, Brazil). Fuel
ethanol samples were analyzed after appropriate dilution in
0.5 mol L−1 NaOH. Gasohol samples could be analyzed after simple
manual liquid/liquid extraction after manual agitation (10 mL
of each—1:1 water/sample) in a closed small flask and subsequent
dilution of an aliquot from the aqueous solution containing ethanol
in 0.5 mol L−1 NaOH. The extraction procedure is similar to the one
used by the Brazilian Association of Technical Standards for the
determination of anhydrous ethanol content in gasohol samples