The comparison of EELS to conventional IR and Raman spectroscopy, the advantage and limitation of EELS. Concept introduction: In an electron energy-loss spectroscopy (EELS), a low energy beam of electron strikes the surface of the sample and excites vibrations. In infrared spectroscopy, the measurement of transmitted infrared radiations is done after they passed through the sample, and in Raman spectroscopy, the scattered radiations in the visible region are measured after they are passed through the sample.

Question

(a 4 shows scanning electron microscope (SEM) images of extruded actions of packing bed for two capillary columns of different diameters, al 750 (bottom image) and b) 30-μm-i.d. Both columns are packed with the same stationary phase, spherical particles with 1-um diameter. A) When the columns were prepared, the figure shows that the column with the larger diameter has more packing irregularities. Explain this observation. B) Predict what affect this should have on band broadening and discuss your prediction using the van Deemter terms. C) Does this figure support your explanations in application question 33? Explain why or why not and make any changes in your answers in light of this figure. Figure 4 SEM images of sections of packed columns for a) 750 and b) 30-um-i.d. capillary columns.³

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Chapter 21, Problem 21.6QAP

Interpretation Introduction

Interpretation:

The comparison of EELS to conventional IR and Raman spectroscopy, the advantage and limitation of EELS.

Concept introduction:

In an electron energy-loss spectroscopy (EELS), a low energy beam of electron strikes the surface of the sample and excites vibrations. In infrared spectroscopy, the measurement of transmitted infrared radiations is done after they passed through the sample, and in Raman spectroscopy, the scattered radiations in the visible region are measured after they are passed through the sample.

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(a 4 shows scanning electron microscope (SEM) images of extruded actions of packing bed for two capillary columns of different diameters, al 750 (bottom image) and b) 30-μm-i.d. Both columns are packed with the same stationary phase, spherical particles with 1-um diameter. A) When the columns were prepared, the figure shows that the column with the larger diameter has more packing irregularities. Explain this observation. B) Predict what affect this should have on band broadening and discuss your prediction using the van Deemter terms. C) Does this figure support your explanations in application question 33? Explain why or why not and make any changes in your answers in light of this figure. Figure 4 SEM images of sections of packed columns for a) 750 and b) 30-um-i.d. capillary columns.³

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34. Figure 3 shows Van Deemter plots for a solute molecule using different column inner diameters (i.d.). A) Predict whether decreasing the column inner diameters increase or decrease bandwidth. B) Predict which van Deemter equation coefficient (A, B, or C) has the greatest effect on increasing or decreasing bandwidth as a function of i.d. and justify your answer. Figure 3 Van Deemter plots for hydroquinone using different column inner diameters (i.d. in μm). The data was obtained from liquid chromatography experiments using fused-silica capillary columns packed with 1.0-μm particles. 35 20 H(um) 큰 20 15 90 0+ 1500 100 75 550 01 02 594 05 μ(cm/sec) 30 15 10