Question

A mixture of two compounds (A and B) was separated by gas chromatography on a non-polar column. The chromatogram was recorded on a chart recorder that fed paper at a constant speed of 100 mm per minute, and a mark was made on the chart when the sample was injected. The first peak on the chromatogram corresponds to compound A, and that peak was observed at a distance of 5.42 cm from the sample injection point, and it had a height of 4.9 cm and a width at half-height of 1.7 cm. The peak corresponding to B was observed at a distance of 8.99 cm from the injection point, and it had a height of 5 cm and a width at half-height of 2.3 cm. What was the percentage of compound A in the mixture?

a. 49.49
b. 50.51
c. 57.99
d. 42.01

Answer 1

Formula to calculate peak = Height * width at half-height

Peak area for compound A

= 4.9cm*1.7cm = 8.33cm2

Peak area for compound B

= 5.0cm *2.3cm = 11.5 cm2

Percentage of compound A

= [Peak area of A/ Total peak area]*100

= [8.33 / (8.33+11.50)]*100

= 42.01

Answer is "Option d"