(a) Calculate the number of theoretical plates for each compound and the average
ID: 502840 • Letter: #
Question
(a) Calculate the number of theoretical plates for each compound and the average number of theoretical plates for the column. (b) Calculate the average height of a theoretical plate, in mm. (c) Explain why it is possible for each compound to have a different number of theoretical plates. (a) Calculate the number of theoretical plates for each compound and the average number of theoretical plates for the column. (b) Calculate the average height of a theoretical plate, in mm. (c) Explain why it is possible for each compound to have a different number of theoretical plates. l. The following data were obtained for four compounds separated on a 20-m capillary column compound (min (min) W 8.04 0.15 8.26 0.15 0.16 8.43 (a) Calculate the number of theoretical plates for each compound and the average number of theoretical plates for the column. (b) Calculate the average height of a theoretical plate, in mm. (c) Explain why it is possible for cach compound to have a different number of theoretical plates.
Explanation / Answer
a) N=number of theoretical plates=16(tR/w)^2=16(8.26/0.15)^2=48517 [compound B)
N=number of theoretical plates=16(tR/w)^2=16(8.04/0.15)^2=45967 [compound A]
N=number of theoretical plates=16(tR/w)^2=16(8.43/0.16)^2=44416 [compound C]
b) H=L/N ,H=height equivalent to theoretical plate,N=number of theoretical plates,L=length of column(mm)
compound A, H=(20 m*1000mm)/m/45967=0.435mm
compound B,H=(20 m*1000mm)/m/48517=0.412mm
compound C,H=(20 m*1000mm)/m/44416=0.450 mm
c)column efficiency is different for different compounds,so different peaks have different retention times,hence different N value .N=number of theoretical plates=16(tR/w)^2 ,w=peak width
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