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Chapter 32: Problem 2

Test your knowledge of chromatographic theory - define the following terms: (a) Dead time \(\left(t_{0}\right)\) (b) Retention time \(\left(t_{\mathrm{R}}\right)\) (c) Capacity factor (k) (d) Separation factor \((\alpha)\) (e) Column efficiency \((N)\).

Short Answer

Expert verified
(a) Dead time is the time it takes for an unretained solute to pass through the system. (b) Retention time is the time from the sample injection to the detection of the peak. (c) Capacity factor is a measure of the column's ability to separate compounds. (d) Separation factor quantifies the differential retention of two analytes. (e) Column efficiency measures the performance of the column in separation.

Step by step solution

01

Define Dead time \(\left(t_{0}\right)\)

Dead time, represented by \(\left(t_{0}\right)\), is the time it takes for an unretained solute to pass through the chromatographic system. It is essentially the time taken for a substance to go through the column without interacting with the stationary phase.
02

Define Retention time \(\left(t_{\mathrm{R}}\right)\)

Retention time, represented by \(\left(t_{R}\right)\), is the time from the injection of the sample to the detection of the analyte's peak. It measures how long a component of the mixture sticks to the column.
03

Define Capacity factor (k)

The capacity factor, represented by \(k\), is a measure of the column's ability to separate compounds. It's calculated as the difference between the retention time and the dead time, divided by the dead time: \(k = (t_R - t_0) / t_0\).
04

Define Separation factor \((\alpha)\)

The separation factor, represented by \(\alpha\), quantifies the differential retention of two analytes. It is the ratio of the capacity factors of two components being separated: \(\alpha = k_2 / k_1\).
05

Define Column efficiency \((N)\)

Column efficiency, represented by \(N\), measures the performance of the column in a chromatographic separation. It is usually measured by the number of theoretical plates. A higher \(N\) value signifies higher column efficiency.

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Most popular questions from this chapter

Test your knowledge of detector terminology. Explain what the following acronyms stand for: (a) \(\mathrm{FID}\) (b) \(\mathrm{TCD}\) (c) \(\mathrm{ECD}\) (d) DAD.

Calculate the capacity factor, resolution and number of theoretical plates of two components from a chromatogram. Quinaldine and nicotine have retention times of \(5.9\) and \(6.2\) min, respectively on a \(30 \mathrm{~cm} \times 0.25 \mathrm{~mm}\) id \(\times 0.25 \mu \mathrm{m}\) film thickness DB5 column. If the peak width of quinaldine is \(0.16\) min and for nicotine is \(0.18 \mathrm{~min}\), calculate (a) Capacity factor for quinaldine and nicotine (b) Column resolution (c) Average number of theoretical plates in the column (column efficiency, \(N\) ) per compound. Note: the retention time of the unretained component is \(1.0 \mathrm{~min}\).

Calculate the resolution and efficiency of two compounds. Compounds \(X\) andY have retention times of \(18.40\) and \(20.63\) min, respectively, on a 30 \(\mathrm{cm}\) column. If the peak widths at the peak bases are \(1.11\) and \(1.21\) min, respectively, calculate: (a) The resolution factor for the two peaks. (b) The efficiency of each peak.

Check your knowledge of liquid chromatography detectors. Make a list of the various major types of liquid chromatography detector in order, from highest to lowest sensitivity. Which of these methods is most versatile and why?
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