Recent advancements in liquid chromatography include the development of ultrahigh pressure liquid chromatography (UHPLC) and an increased use of capillary columns that had previously only been used with gas chromatography. Both of these advances have made the development of portable LC systems possible. For example, Axcend Corp. makes a portable system that uses a capillary column with an internal diameter of 150-μm-that is packed with 1.7-um stationary phase particles. In contrast, a traditional LC column has a 4.6 mm internal diameter and utilizes 5-um stationary phase particles. a) Explain one advantage that is afforded by the use of a capillary column in liquid chromatographic separation. Explain one disadvantage of capillary columns. b) Explain how the use of smaller stationary phase particles can improve the resolution of a separation. Include any relevant equations that support your explanation. c) A scientist at Rowan University is using the Axcend LC to conduct analyses of F pharmaceutical and illicit drugs. Figure 3F from his paper (copied here) shows the separation of morphine (peak 18) and its metabolites: 6-acetylmorphine (peak 19) and heroin (peak 20). Look up the structures of these molecules. Based on the structures of these compounds, do you believe this method used reversed- or normal-phase partition chromatography? Be sure to explain how you came to this conclusion. Signal (MAU) 4.0 3.5 30 25- 1.5 1.0 0.5- 0.0 24 26 28 3.0 20 3.2 3.4 3.6 3.8 4.0 4.2 44 Time (min) d) Use peaks 19 and 20 of the above chromatogram to calculate the resolution (R) and the number of theoretical plates (M) for this column. e) In the analysis of morphine and its metabolites using this portable LC, there is a lot of "dead time" between the elution of each analyte. Propose two parameters that could be adjusted to reduce wasted time without compromising the quality of the separation (as shown, the method is being run as a gradient elution with a flow rate of 2 µL/min). Explain the theory that supports your proposed changes.
Recent advancements in liquid chromatography include the development of ultrahigh pressure liquid chromatography (UHPLC) and an increased use of capillary columns that had previously only been used with gas chromatography. Both of these advances have made the development of portable LC systems possible. For example, Axcend Corp. makes a portable system that uses a capillary column with an internal diameter of 150-μm-that is packed with 1.7-um stationary phase particles. In contrast, a traditional LC column has a 4.6 mm internal diameter and utilizes 5-um stationary phase particles. a) Explain one advantage that is afforded by the use of a capillary column in liquid chromatographic separation. Explain one disadvantage of capillary columns. b) Explain how the use of smaller stationary phase particles can improve the resolution of a separation. Include any relevant equations that support your explanation. c) A scientist at Rowan University is using the Axcend LC to conduct analyses of F pharmaceutical and illicit drugs. Figure 3F from his paper (copied here) shows the separation of morphine (peak 18) and its metabolites: 6-acetylmorphine (peak 19) and heroin (peak 20). Look up the structures of these molecules. Based on the structures of these compounds, do you believe this method used reversed- or normal-phase partition chromatography? Be sure to explain how you came to this conclusion. Signal (MAU) 4.0 3.5 30 25- 1.5 1.0 0.5- 0.0 24 26 28 3.0 20 3.2 3.4 3.6 3.8 4.0 4.2 44 Time (min) d) Use peaks 19 and 20 of the above chromatogram to calculate the resolution (R) and the number of theoretical plates (M) for this column. e) In the analysis of morphine and its metabolites using this portable LC, there is a lot of "dead time" between the elution of each analyte. Propose two parameters that could be adjusted to reduce wasted time without compromising the quality of the separation (as shown, the method is being run as a gradient elution with a flow rate of 2 µL/min). Explain the theory that supports your proposed changes.
Macroscale and Microscale Organic Experiments
7th Edition
ISBN:9781305577190
Author:Kenneth L. Williamson, Katherine M. Masters
Publisher:Kenneth L. Williamson, Katherine M. Masters
Chapter9: Column Chromatography: Fluorenone, Cholesteryl Acetate, Acetylferrocene, And Plant Pigments
Section: Chapter Questions
Problem 5Q
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Question
Transcribed Image Text:Recent advancements in liquid chromatography include the development of ultrahigh pressure liquid
chromatography (UHPLC) and an increased use of capillary columns that had previously only been used
with gas chromatography. Both of these advances have made the development of portable LC systems
possible. For example, Axcend Corp. makes a portable system that uses a capillary column with an
internal diameter of 150-μm-that is packed with 1.7-um stationary phase particles. In contrast, a traditional
LC column has a 4.6 mm internal diameter and utilizes 5-um stationary phase particles.
a) Explain one advantage that is afforded by the use of a capillary column in liquid chromatographic
separation. Explain one disadvantage of capillary columns.
b) Explain how the use of smaller stationary phase particles can improve the resolution of a separation.
Include any relevant equations that support your explanation.
c) A scientist at Rowan University is using
the Axcend LC to conduct analyses of F
pharmaceutical and illicit drugs. Figure 3F
from his paper (copied here) shows the
separation of morphine (peak 18) and its
metabolites: 6-acetylmorphine (peak 19)
and heroin (peak 20). Look up the
structures of these molecules. Based on the
structures of these compounds, do you
believe this method used reversed- or
normal-phase partition chromatography?
Be sure to explain how you came to this
conclusion.
Signal (MAU)
4.0
3.5
30
25-
1.5
1.0
0.5-
0.0
24 26 28 3.0
20
3.2 3.4 3.6 3.8 4.0 4.2 44
Time (min)
d) Use peaks 19 and 20 of the above
chromatogram to calculate the resolution (R) and the number of theoretical plates (M) for this
column.
e) In the analysis of morphine and its metabolites using this portable LC, there is a lot of "dead time"
between the elution of each analyte. Propose two parameters that could be adjusted to reduce wasted
time without compromising the quality of the separation (as shown, the method is being run as a
gradient elution with a flow rate of 2 µL/min). Explain the theory that supports your proposed
changes.
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