# Chemical Forums

## Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: zeshkani on April 12, 2008, 09:25:17 PM

Title: % ethanol in Vodka via GC
Post by: zeshkani on April 12, 2008, 09:25:17 PM
this is the question:
predict the ethanol percentage in vodka sample (0.7mL) and provide a uncertainty in the predicted value ?

the vodka sample was combined with a 40% 1-propanol solution, we used 0.7mL 1-propanol and used 0.7mL of vodka, according to the GC Plot that we got,
the ethanol in Vodka                            The 1-propanol
Area % = 9.883                                Area % = 7.264
Height (µV.Min) = 1178.4                   Height (µV.Min) = 734.5
Area (µV.Min) = 12.7                         Area (µV.Min) = 9.3
Retention time = 1.09Min                   Retention time = 1.2

so from here were do i even start, since i need the (v/v)% ethanol
the equation for (v/v)% = (Volume of solute)/ (Total Volume of solution)
but i cant use this since i dont know the volume of ethanol in vodka at 0.7mL
maybe somebody can point in the right direction on how to solve this
Thx
Title: Re: % ethanol in Vodka via GC
Post by: Arkcon on April 12, 2008, 09:33:03 PM
You don't know exactly how much ethanol there is, but you do know exactly how much iso-propanol there is, right?  And you got an area for IPA, right.  So you can compare the two.  You want a tough chromatography problem, look at this one:  http://www.chemicalforums.com/index.php?topic=25535.msg96375#msg96375