(a) On Column X, Compound A has a retention time of 2.15 minutes, and a peak wid

Question

(a) On Column X, Compound A has a retention time of 2.15 minutes, and a peak width of 0.27 minutes, while Compound B has a retention time of 2.7 minutes and a peak width of 0.8 minutes. On Column Y, Compound A has a retention time of 2.15 minutes, and a peak width of 0.13 minutes, while Compound B has a retention time of 2.5 minutes and a peak width of 0.18 minutes. For both columns, the void time is 1.06 minutes Calculate the following: (Gi) the number of plates (NA and NB) for Component A and Component B (ii) the resolution between Component A and B using width at baseline for (ii reslution between Component A and Component B using the Purnell for both columns; both columns; equation Hint: N NANa) for both columns. (b) Sketch and label the chromatogram obtained on each column in part (a).

Explanation / Answer

Part (a)

1) No. of plates (N) accounts for effectiveness of a column in column chromatography.

According to Tangent Line Method , the equation to calculate no. of plates (N) is,

N = 16 * (Tr / W)2

N = No. of plates

Tr = Retention time and W = Peak width

For component A in column X

NA = 16 * (Tr / WA)2

   = 16 * (2.15 min / 0.27 min)2

   = 16 * 63.41

= 1014.56

NA = 1015 (approx.)

For component B in column X

NB = 16 * (Tr / WB)2

= 16 * (2.7 min/0.8 min) 2

= 16 * 11.39

= 182.25

NB= 182 (approx..)

For component A in column Y

NA = 16 * (Tr / WA)2

= 16 * (2.15 min/0.13 min) 2

= 16 * 273.52

= 4376.32

NA = 4376 (approx..)

For component B in column Y

NB = 16 * (Tr / WB)2

= 16 * (2.5 min/0.18 min) 2

= 16 * 192.90

= 3086.4

NB = 3086 (approx..)

2) Resolution :

In a particular column, two peaks are obtained from two components. The quantitative measure of separation between two peaks is called resolution.

Equation to calculate chromatographic resolution is,

RAB = 2 ( tr,A - tr,B ) / (WB + WA)

RAB = Resolution between two peaks obtained from two components

tr,A = Retention time of component A

tr,B = Retention time of component B

For column X

RAB = 2 ( tr,A - tr,B ) / (WB + WA)

      = 2 ( 2.15 – 2.70 ) / (0.27 + 0.80)

      = - 1.028

But resolution can not be negative. We shall take the ‘mod’ value. Hence resolution of column X is 1.028

For column Y

RAB = 2 ( tr,A - tr,B ) / (WB + WA)

      = 2 ( 2.15 – 2.50 ) / (0.13 + 0.18)

      = - 2.258

But resolution can not be negative. We shall take the ‘mod’ value. Hence resolution of column Y is 2.258

We could take tr,B - tr,A either in above equation.

3) Insufficient data

Part (B)

See the diagram below -

https://drive.google.com/open?id=1sETLMmMnrkCKIaNY4ixCElKeH-BskAtQ

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