The following data are for a liquid chromatographic column:
Length of packing (L) 24.7 cm
Flow rate 0.313 mL/min
VM 1.37 mL
VS 0.164 mL
A chromatogram of a mixture of species A, B, C and D provided the following data
Retention time
Nonretained 3.1 -
A = 5.4
B = 13.3
C = 14.1
D = 21.6
Width of peak
A = 0.41
B= 1.07
C= 1.16
D= 1.72
Calculate the Retention Factor for A,B,C and D.
I've done that...
A= 0.74
B= 3.29
C= 5.96
D= 4.44
Calculate the Distribution constant for A,B,C and D? (having trouble here)
And Calculate the following..
(a) the number of plates from each peak and the mean.
Number of plates = 16*tr^2/w^2
a = 2775.49
b = 2472.04
c = 2363.97
d = 2523.30
mean = 2533.7
(b) the plate height for the column. (having lots of trouble here)
Calculate for species B and C,
The selectivity factor = tr'2/tr'1
which = 3.54/3.29
= 1.07
the length of column necessary to separate the two species with a resolution of 1.5. ( I cant do this one please help)
Thanks, to whoever helps me out with this, I am having so much trouble
The retention time looks good for A, except that you should have 0.792-- one more significant figure, so I will move on to the next problem. This is only for A, and I think you can perform the rest after I am done. To solve for the distribution constant, perform the following:
k=K/Beta
Where
k=0.74
Beta=VM/VS=1.37 mL/0.164 mL
and
K=???
Solve for K:
K=0.74*(1.37 mL/0.164 mL)
K=0.74*8.354
K=6.18
For the number of plates:
Use the following equation:
N=16*(Tr/W)^2
Where
Tr=5.4
W=0.41
and
N=???
Solve for N:
N=16*(5.4/0.42)^2
N=2.64 x 10^3
*** I'll let you solve for the mean.
For the plate height, use the following equation:
N=L/H
Where
N=2.64 x 10^3
L=24.7 cm
and
H=??
Solve for H:
L/N=H
24.7 cm/2.64 x 10^3=H
H=0.00934=9.34 x 10^-3
For the selectivity factor, it looks good, but we have a difference in the last significant figure:
Use the equation below and solve for alpha:
Alpha=tr2/tr1
Where
tr'2=14.1
and
tr'1=13.5
Alpha=14.1/13.5=1.04
I don’t understand the answer do it for me step by step so I can understand it
How do I solve the mean
To calculate the distribution constant for A, B, C, and D, you need to use the following formula:
Distribution constant (K) = (Retention factor (R) - 1) / Retention factor (R)
For species A, the retention factor (R) is 0.74. Therefore:
K for A = (0.74 - 1) / 0.74 = -0.35/0.74 = -0.47
Similarly, you can calculate the distribution constant for B, C, and D using their respective retention factors.
For the plate height (H) of the column, you can use the following equation:
H = Length of Packing (L) / (5.54 * Number of Plates)
To calculate the plate height for species B, use the value of L (24.7 cm) and the number of plates you calculated (2472.04).
H for B = 24.7 / (5.54 * 2472.04) = 24.7 / 13,670.72 = 0.0018 cm
Similarly, you can calculate the plate height for species C using the number of plates obtained for species C.
To determine the length of column necessary to separate species B and C with a resolution of 1.5, you need to use the following formula:
L = (5.54 * (tr'C - tr'B))² / (16 * (H² + H²))
Here, tr'C represents the retention time of species C, and tr'B represents the retention time of species B. H is the plate height you calculated for species B.
Substitute the values and calculate the length (L) required to achieve a resolution of 1.5.
I hope this helps! If you have any further questions, feel free to ask.