Normalized Intensity (a. u.) 0.5 1.0 A 3D-printed GC column (shown below) was created for use with "micro" gas chromatography applications. To prove its utility, it was used to separate a mixture of alkanes (C9-C18, C22, C24). For the separation shown below, the column temperature was ramped from 40 °C to 250 °C at a rate of 30 °C per minute. (a) 9 10 = 1 mm 12 13 15 22 0.0 0 100 200 300 400 Time (sec) a) What detector would you use for this analysis? Justify your selection. b) Explain how the chromatogram would change if the separation was run isothermally. c) Explain how the chromatogram would change if the temperature ramp were increased to 50 °C per minute.

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

1) Study the chromatograph (below) of a mixture of Compounds A and B, run on the GCs in the teaching labs at CU Boulder. Compound A has the shorter retention time. STAAT 61 1.11 227 RT TYPE AREA XXXX XXXX XXXX AREAS 0.009 55874 44.117 ARIHT 0.61 XX XX XX 1.11 2.27 XX XX XX TOTAL AREA=XX MUL FACTOR=XX 1. What is the retention time of compound A? Compound B? 2. Which compound is present in a larger amount? 3. Which compound has the lower boiling point? 4. What would happen to the retention times of compounds A and B if the column temperature were raised? 5. You suspect that compound B is octane. What can you do to provide supporting evidence for this hypothesis?

Study the chromatograph (below) of a mixture of Compounds A and B, run on the GCs in the teaching labs at CU Boulder. Compound A has the shorter retention time. You suspect that compound B is octane. What can you do to provide supporting evidence for this hypothesis?

1. From spinach, the chromatographic analysis will yield two major substances: (a) B-carotene (C40H56), which will separate from the spinach mixture to form a yellow band, and (b) chlorophyll A (CSSH72MGN4OS), which will separate from the mixture to form a green band. i. Describe the characteristics and draw structures of these molecules. ii. From the spectrophotometric analysis, what wavelength (Amax) would you expect ß-carotene (C40H56) to absorb? What wavelength would chlorophyll A (CssH72MgN4O5) absorb?

Please don't provide handwritten solution ...

6

1c

A gas chromatography column containing a poly(dimethylsiloxane) stationary phase is used to separate the molecules listed. Place the molecules in the order they will elute from the column. Refer to a list of retention indexes for several molecules. Elutes first hexane benzene heptane 2-pentanone 1-nitropropane octane Elutes last Anawer Bank

What is 4d?