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Which column is more efficient: plate height = 0.1 mm or plate height = 1 mm?

Short Answer

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The solution is

the column with a lower plate height of 0.1 mm would be preferred. Because there would be less band dispersion, it would be more efficient.

Step by step solution

01

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In this job, we'll see whether column is more efficient: one with a plate height = 0.1 mm or one with a plate height =1 mm.

02

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Consider the van Deemter equation, which explains how plate height is affected by column and flow rate:

H=A+Bux+C×ux

where denotes numerous pathways, Buxdenotes longitudinal diffusion, and denotes equilibration time.

- In addition, the following is the formula for plate height:

H=LNN=LH

1. The value of H = 0.1 mm is inversely proportional to the value of (lower H=larger N ).

2. The size of H = 1.0 mm is inversely proportional to the size of N (larger H=smaller N ).

03

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Examine the Purnell equation for resolution now:

Resolution =N4α-1αk21+k2

1. The resolution is proportional toN (the larger the N , the higher the resolution).

2. Resolution is proportional toN (lower N = lower resolution).

04

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As a result, the column with a lower plate height of 0.1 would be preferred. Because there would be less band dispersion, it would be more efficient

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Most popular questions from this chapter

(a) Explain why the diffusion coefficient of CH3OHis greater than that of

sucrose in Table 23-1.

(b) Make an order-of-magnitude estimate of the diffusion coefficient of water

vapor in air at 298K.

A chromatographic procedure separatesof unknown mixture on a column with a length of 40cmand a diameter of 0.85cm . (a) What size column would you use to separate 100mgof the same mixture? (b) If the flow is 0.22mL/minon the small column, what volume flow rate should be used on the large column? (c) The mobile phase occupies 35%of the column volume. Calculate the linear velocity for the small column and the large column.

23-41. Describe how nonlinear partition isotherms lead to non-Gaussian band shapes. Draw the chromatographic peak shapes produced by an overloaded gas chromatography column and an overloaded liquid chromatography column.

23-42. A separation of 2.5mgof an unknown mixture has been optimized on a column of length L and diameter d .

(a) Explain why you might not achieve the same resolution if the 2.5mgof unknown mixture were injected in twice the injection volume.

(b) Explain why you might not achieve the same resolution if5.0mg of unknown mixture were injected in the original injection volume.

A Gas chromatogram of a mixture of toluene and ethyl acetate is shown here:

(a)Use the width of each peak (measured at the base)to calculate the number of theoretical plates in the column. Estimate all lengths to the nearest 0.1 mm.

(b)Using the width of the toluene peak at its base, calculate the width expected at half height. Compare the measured and calculated values. When the thickness of the the line is significant relative to the length being measured, it is important to take the pen line width into account. You can measure from the edge of one line to the corresponding edge of the other line,as shown here.

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