Chapter 27, Problem 27.26QAP

Interpretation Introduction

Interpretation:

Percentages of each component should be calculated.

Concept introduction:

Area normalization method is used in quantitative analysis of compounds in chromatography. In this method of quantification, complete elution of all analytes in the sample is required. Following formulas are required for the calculation.

$\begin{array}{l}\text{Corrected}\text{area=Relative}\text{area×}\text{Relative}\text{detector}\text{response}\\ \text{Percentage}\text{of}\text{the}\text{compound=}\frac{\text{Corrected}\text{area}\text{of}\text{interested}\text{compound}}{\text{Total}\text{corrected}\text{area}}\text{×100\%}\end{array}$

Answer to Problem 27.26QAP

$\begin{array}{l}\text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{A}}\text{=19}\text{.1\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{B}}\text{=12}\text{.5\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{C}}\text{=37}\text{.8\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{D}}\text{=18}\text{.5\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{E}}\text{=11}\text{.9\%}\end{array}$

Explanation of Solution

Given information:

Compound	Relative peak area	Relative detector response
A	32.5	0.70
B	20.7	0.72
C	60.1	0.75
D	30.2	0.73
E	18.3	0.78

Corrected areas of compound can be calculated as follows.

$\begin{array}{l}Correctedare{a}_A=Relativearea\times Relativedetectorresponse\\ =32.5\times 0.70\\ =22.75\\ Correctedare{a}_B=Relativearea\times Relativedetectorresponse\\ =20.7\times 0.72\\ =14.90\\ Correctedare{a}_C=Relativearea\times Relativedetectorresponse\\ =60.1\times 0.75\\ =45.08\\ Correctedare{a}_D=Relativearea\times Relativedetectorresponse\\ =30.2\times 0.73\\ =22.05\\ Correctedare{a}_E=Relativearea\times Relativedetectorresponse\\ =18.3\times 0.78\\ =14.27\\ Totalcorrectedarea=22.75+14.9+45.08+22.05+14.27\\ =119.05\end{array}$

Now, the percentage of compound can be calculated as follows:

$\begin{array}{l}\text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{A}}\text{=}\frac{\text{Corrected}\text{area}\text{of}\text{interested}\text{compound}}{\text{Total}\text{corrected}\text{area}}\text{×100\%}\\ \text{=}\frac{\text{22}\text{.75}}{\text{119}\text{.05}}\text{×100\%}\\ \text{=19}\text{.1\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{B}}\text{=}\frac{\text{Corrected}\text{area}\text{of}\text{interested}\text{compound}}{\text{Total}\text{corrected}\text{area}}\text{×100\%}\\ \text{=}\frac{\text{14}\text{.9}}{\text{119}\text{.05}}\text{×100\%}\\ \text{=12}\text{.5\%}\end{array}$

Or,

$\begin{array}{l}\text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{C}}\text{=}\frac{\text{Corrected}\text{area}\text{of}\text{interested}\text{compound}}{\text{Total}\text{corrected}\text{area}}\text{×100\%}\\ \text{=}\frac{\text{45}\text{.08}}{\text{119}\text{.05}}\text{×100\%}\\ \text{=37}\text{.8\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{D}}\text{=}\frac{\text{Corrected}\text{area}\text{of}\text{interested}\text{compound}}{\text{Total}\text{corrected}\text{area}}\text{×100\%}\\ \text{=}\frac{\text{22}\text{.05}}{\text{119}\text{.05}}\text{×100\%}\\ \text{=18}\text{.5\%}\end{array}$

Also,

$\begin{array}{l}\text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{E}}\text{=}\frac{\text{Corrected}\text{area}\text{of}\text{interested}\text{compound}}{\text{Total}\text{corrected}\text{area}}\text{×100\%}\\ \text{=}\frac{\text{14}\text{.27}}{\text{119}\text{.05}}\text{×100\%}\\ \text{=11}\text{.9\%}\end{array}$

Conclusion

Thus,

$\begin{array}{l}\text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{A}}\text{=19}\text{.1\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{B}}\text{=12}\text{.5\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{C}}\text{=37}\text{.8\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{D}}\text{=18}\text{.5\%}\\ \text{Percentage}\text{of}\text{the}{\text{compound}}_{\text{E}}\text{=11}\text{.9\%}\end{array}$