The following questions apply to separation of a solution containing pentanol (F

Question

The following questions apply to separation of a solution containing pentanol (FM 88.15) and 2,3-dimethyl-2-butanol (FM 102.17). Pentanol is the internal standard. Only need answer for part A and C. Part B is correct

a) Separation of a standard solution containing 225 mg of pentanol and 255 mg of 2,3-dimethyl-2-butand Map 0 mL of solution led to a pentanol:2,3-dimethyl-2-butanol relative peak area ratio of 0.880:1.00. Calcula the response factor, F, for 2,3-dimethyl-2-butanol Incorrect In part (a), calculate the response factor, F, from the relative peak areas and the concentrations using the equation Number 0.865 Calculate the areas for pentanol and 2,3-dimethyl-2-butanol gas chromatogram peaks in an unknown or pentanol, the peak height was 23.0 mm and the width at half-height was 3.8 mm. For 2,3-dimethyl-2 butanol, the peak height was 85.8 mm and the width at half-height was 2.0 mm. Assume each peak to be a Gaussian where Ax and X] are the relative peak area and concentration of 2,3-dimethyl-2-butanol, and As Number and [S] are the relative peak area and Pentanol 92.99 concentration of pentanol, the internal standard Number 2,3-Dimethyl-2-butanol 182.6 (Scroll down for more questions.) (c) If the concentration of pentanol in the unknown solution of part (b) was 75.0 mM, what was the 2,3- dimethyl-2-butanol concentration? Number 170 m M

Explanation / Answer

A) Given data:

For pentanol; [Pentanol] = 225 mg/10 mL = 22.5 mg/mL,

For 2,3-Dimethyl-2-butanol; [2,3-Dimethyl-2-butanol] = 255 mg/10 mL = 25.5 mg/mL.

And Apentanol : A2,3-Dimethyl-2-butanol = 0.880:1.00.

A2,3-Dimethyl-2-butanol / Apentanol = 1.00 :0.880

Relative response factor for 2,3-Dimethyl-2-butanol (F),

Formula,

F = (A2,3-Dimethyl-2-butanol /[2,3-Dimethyl-2-butanol]) / (Apentanol /[Pentanol])

i.e. F = (A2,3-Dimethyl-2-butanol x [Pentanol]) /( Apentanol x[2,3-Dimethyl-2-butanol])

F = (A2,3-Dimethyl-2-butanol / Apentanol) x ([Pentanol]/ [2,3-Dimethyl-2-butanol])

F = (1.00/0.880) x (22.5/25.5)

F = 1.136 x 0.882

F = 1.003

Relative response factor for [2,3-Dimethyl-2-butanol] = 1.003.

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C)Let,

For pentanol; [Pentanol] = 75.0 mM,

For 2,3-Dimethyl-2-butanol; [2,3-Dimethyl-2-butanol] = ?

And Apentanol : A2,3-Dimethyl-2-butanol = 0.880:1.00.

A2,3-Dimethyl-2-butanol / Apentanol = 1.00 :0.880

Relative response factor for 2,3-Dimethyl-2-butanol (F) = 1.003,

Formula,

F = (A2,3-Dimethyl-2-butanol /[2,3-Dimethyl-2-butanol]) / (Apentanol /[Pentanol])

i.e. F = (A2,3-Dimethyl-2-butanol x [Pentanol]) /( Apentanol x[2,3-Dimethyl-2-butanol])

F = (A2,3-Dimethyl-2-butanol / Apentanol) x ([Pentanol]/ [2,3-Dimethyl-2-butanol])

Let us put all known values,

1.003 = (1.00/0.880) x (75.0/[2,3-Dimethyl-2-butanol])

1.003 = 1.136 x (75.0/[2,3-Dimethyl-2-butanol])

(75.0/[2,3-Dimethyl-2-butanol]) = 1.003/1.136

(75.0/[2,3-Dimethyl-2-butanol]) = 0.883

[2,3-Dimethyl-2-butanol] = 75.0/0.883

[2,3-Dimethyl-2-butanol] = 84.94 mM = 85 mM (apprx.).

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