Please help! not sure how to calculate Cunk. B. Unknown Mixture Multiple injecti
ID: 835594 • Letter: P
Question
Please help! not sure how to calculate Cunk.
B. Unknown Mixture Multiple injections of a sample will usually result in different peak areas for a given component because it is difficult to reproduce the injection volume. These variations are compensated for by adjusting (normalizing) the component peak area by dividing it by the peak area of the internal standard (decane). In this way the concentration of each component in your unknown can be determined by a simple comparison of normalized peak areas:
[(Component AREA/Decane AREA)unk / (Component AREA/Decane AREA)std] = Cunk/Cstd
where (Component AREA/Decane AREA)unk is the normalized peak area for a particular component in the unknown solution, (Component AREA/Decane AREA)std is the average normalized peak area for a particular component in the standard solution, and Cunk and Cstd are the unknown and standard concentrations of that component, respectively. Report the mean concentration and its RMD for each component of the unknown. The precision of your results should be 2-3%.
Explanation / Answer
A)
Here, the number of theoretical plates (N) for octane using: N=16(tR/w)^2
where tR = retention time and W is the magnitude of the base of the triangle defining the octane
So, respectively:
For octane piking the data from serial no 2.
2.) tR = 2.445 min = 2.445 * 60 s = 146.7 s
, Area = (1/2) * H *W
W = (2 * area) / H
= 2 * (Area/ Height ) s
= 2 * 1.6770 s
= 3.354 s
Therefore, number of theoretical plates (N) for octane using:
N=16(tR/w)^2
= 16*( 146.7 / 3.354) ^2
= 30609 ( approx)
B).Since,
[(Component AREA/Decane AREA)unk / (Component AREA/Decane AREA)std] = Cunk/Cstd
where (Component AREA/Decane AREA)unk is the normalized peak area for a particular component in the unknown solution, (Component AREA/Decane AREA)std is the average normalized peak area for a particular component in the standard solution, and Cunk and Cstd are the unknown and standard concentrations of that component, respectively.
Here, Standard solution is decane
Then, then.
4210975.59 / 676082.01 = Cunk/Cstd
As you have not mentioned the dtrenght of std solution. Let take the std ,soluion as 1 M.
Then, Cunk = (4210975.59 / 676082.01 ) * 1
= 6.228 M
You can further refer to the below refrence for solving the problem, it will really help you, as you have not provided the full information about the question.
Refrence : http://www.chemistry.adelaide.edu.au/external/soc-rel/content/int-std.htm