Data/Observations: In the chromatogram of a mixture of cyclohexanol and heptanal, there are 8 peaks. Retention times are 1.783, 2.111, 2.181, 2.832, 3.798, 4.012, 4.268, and 4.351 (min) in an increasing order. Areas are 5193372, 27743, 1333, 1283, 4005, 1734332, 3526677, and 2079050. Each area corresponds to each retention times.
Calculations & Results: -Student mixture (cyclohexanol and heptanal)- Retention times of peak# 6, 7, and 8 from the student mixture look similar to the standard retention times of cyclohexanol and heptanal. The first peak has the largest area; 5193372, it is about a half of the total area, and the fourth peak is the smallest area, 1283. From 5 and 8 peaks, they are merged together rather than a straight line for …show more content…
As the retention time of the standard cyclohexanol is 3.959 min, the sixth peak (4.012) of the student mixture, the closest peak, represents cyclohexanol. In the same way, the seventh peak (4.268) represents heptanal whose standard retention time is 4.170. The order of the retention times corresponds to their polarity; polar analyte interacts more strongly with polar columns. Cyclohexanol has one electronegative atom with only 6 carbons, but heptanal has one electronegative atom with 7 carbons. Therefore, cyclohexanol is relatively polar than …show more content…
Based on the data presented in the Data Set A chromatographic separation, can you explain why there is such a steep decline in column efficiency with temperature change?
As the temperature is increasing, the equilibrium partitioning of the sample with the stationary phase will not be established. Then, the components of the mixture may elute together or be incompletely separated. To sum up, as the temperature increases, the number of theoretical plates decreases, the efficiency decreases.
6-19 Consider the above gas chromatogram for a mixture of analytes X and Y: Calculate the number of theoretical plates for the column in reference to the peaks of each component (X and Y)
Based on the graph, Wx is 45s, Wy is 30s, tR,x is 235s, and tR,y is 280s.
Theoretical plates for X are 16(235/45)2=436.346
Theoretical plates for Y are 16(280/30)2=1393.777 If the column is 12 m long, calculate the height equivalent theoretical plate (HEPT, in plates per cm) for this
Calculations & Results: -Student mixture (cyclohexanol and heptanal)- Retention times of peak# 6, 7, and 8 from the student mixture look similar to the standard retention times of cyclohexanol and heptanal. The first peak has the largest area; 5193372, it is about a half of the total area, and the fourth peak is the smallest area, 1283. From 5 and 8 peaks, they are merged together rather than a straight line for …show more content…
As the retention time of the standard cyclohexanol is 3.959 min, the sixth peak (4.012) of the student mixture, the closest peak, represents cyclohexanol. In the same way, the seventh peak (4.268) represents heptanal whose standard retention time is 4.170. The order of the retention times corresponds to their polarity; polar analyte interacts more strongly with polar columns. Cyclohexanol has one electronegative atom with only 6 carbons, but heptanal has one electronegative atom with 7 carbons. Therefore, cyclohexanol is relatively polar than …show more content…
Based on the data presented in the Data Set A chromatographic separation, can you explain why there is such a steep decline in column efficiency with temperature change?
As the temperature is increasing, the equilibrium partitioning of the sample with the stationary phase will not be established. Then, the components of the mixture may elute together or be incompletely separated. To sum up, as the temperature increases, the number of theoretical plates decreases, the efficiency decreases.
6-19 Consider the above gas chromatogram for a mixture of analytes X and Y: Calculate the number of theoretical plates for the column in reference to the peaks of each component (X and Y)
Based on the graph, Wx is 45s, Wy is 30s, tR,x is 235s, and tR,y is 280s.
Theoretical plates for X are 16(235/45)2=436.346
Theoretical plates for Y are 16(280/30)2=1393.777 If the column is 12 m long, calculate the height equivalent theoretical plate (HEPT, in plates per cm) for this