Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: payata on April 16, 2019, 08:40:19 AM

Hey Guys!
I have a problem with task below, hope you can navigate/ help me with it ???
In a 100 mL measuring flask 30 µL of butan1ol is placed by pipetting, The flask is filled to the mark with technical grade acetone,
The solution is analysed once and the following areas are found:
Area of
propan2ol 854
Area of
butan1ol 405
Calculate the concentration (v/v%) of propan2ol in the sample, Show the calculations:
What I did until now, I deviated Area of sample / Area of Internal standard (which is butan1ol, 0,03% v/v), I know that concentration I should find by drawing standard curve, but how if concentration is not given?
So formula should looks like that: c= (Area of sample/Area of IS  intercept)/slope . but, how to calculate concetration to draw std curve? ???
Thank you in advance!

The only thing you can do it to assume signal to be directly proportional to the surface area.
This is equivalent to assuming at C=0 Area=0  this way you have two points to build your curve on.

I'm not quite sure if assumec=0, please look below
the answer is given c= (854/405+0,0116)/35,529 = 0,0597%
this is what the Lecturer gave to us ??? and I really do not how he got intercept, and slope for that, plus concentration

There is no way to derive the formula used from the numbers given, so either you are missing something (earlier part of the lecture, page in a book, whatever), or you were given incomplete data.

All class got same as I, so I think I will write to Lecturer and confirm :D
Thank you for reply!