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.

A student performed chromatography on a mixture of benzoic acid (C6H5CO₂H), acetophenone (C6H5C(O)CH3) and styrene (C6H5CHCH₂). She used alumina (Al₂O3) as the stationary phase and a 9 : 1 mixture of hexane : ethyl ethanoate as the mobile phase. Rank the order in which the compounds moved, from fastest to slowest. benzoic acid acetophenone styrene

A young researcher set out to develop a method for quantifying the polycyclic aromatic hydrocarbon (PAH) content in a contaminated soil sample using open tubular gas chromatography. During the initial stages of method development, the researcher was unable to separate the early eluting compounds, anthracene and naphthalene, with baseline resolution. Select the possible modifications the researcher could make to improve the resolution. use a column with a smaller inner diameter decrease the column length increase the stationary phase thickness increase the temperature choose a different stationary phase

Which of the following are characteristics of normal-phase chromatography?  I - The stationary phase is polar.  II - The mobile phase is more polar than the stationary phase.  III - The eluent strength increases as the mobile phase becomes less polar.  IV - The eluent strength increases as the mobile phase becomes more polar.  V - the stationary phase is nonpolar.    Answers to choose from:  I and IV I, IV and V I and III II and IV II and V ...and why?

Please answer Questions 5-3, 5-4, and 5-5 (GC Gas Chromatography) 5-2. A sample mixture of ethyl benzoate (bp 212 Celsius) and dodecane (bp 216.2 Celsius) is injected on two GC columns.Column A has DC710 silicone oil as the stationary phase, and column B uses polyethylene glycol as the stationaryphase. Which substance would be certain to elute first from column A and would the same material be expected toelute first from column B? Which column, A or B, would be expected to give the better separation of these two substances? 5-3. Question 5-2 refers to separating a mixture of two high boiling liquids by gas chromatography. These materials havesimilar boiling points. List several GC variables and conditions that would make it easier to separate thesesubstances by gas chromatography. 5-4. Capillary GC columns have better resolution than packed columns even though the enormous surface area provided by the packing material is absent in capillary columns. Why? 5-5. Preparative GC requires…

True or False: Liquid-solid  phase column chromatography is used to separate large up to multigram amounts of mixtures, based on their differences (however small) in polarity.

anch of the following components cannot be detected by gas chromatography? 4 Essential oils Alcohols b) Volatile compounds d) Non-volatile compounds 13- is measured as time elapsed from the point of injection to the peak maximum? a)-Column efficiency d)- Delectability c)-Retention time 14- Which of the following can be used to detect the components in gas chromatography a) non-volatile compounds b) volatile compounds c) Salts d) b&c 15-Which of the following methods is often referred to as mechanical separation processes. a)-Gas Chromatography b)-column chromatography c)- Sedimentation 16- For obtaining better resolution in TLC. and then developed with a second solvent at right angles to the first a) Stepwise b) Descending e) Ascending 17- This is defined as transport of electrically charged particles in a direct-current electric field a) ion exchange chromatography b) Electrophoresis c) ultracentrifuge d) exclusion 18-This figure indicates to schematic Diagram of a) Gas chromatography…

An internal standard is incorporated into an analysis method when systematic sources of variation (i.e., variation not under statistical control) exist that cannot be eliminated. A sample must be injected into the chromatographic system in order for it to be analyzed using HPLC. Which type of injection mode would create the largest source of systematic variation? automated sample injector manual sample injector

You have obtained a gas chromatogram of a two component mixture of compounds A and B. The height of peak A is 3.84 cm. and the width at half height is 1 cm. The height of peak B is 3.49 cm. and the width at half height is 1.36 cm. The percentage of a component in the mixture is proportional to peak area. Estimate peak areas by multiplying height by width at half height. What was the percentage of compound B in the mixture? (Enter your answer as a number without any percent symbol or the word percent.)

Use a chemical dictionary, chemical text or encyclopedia to find a specific definition of "chromatography." List a few mobile and stationary phases.