Sample/practice exam 2015, questions - test 2 PDF

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Test 2...

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CHEM 3590 Instrumental Analysis Practice questions for Test 2 Note: for the test you will be asked to answer 8 questions out of 10.

QUESTION 1: Given the four following compounds: Acetone, acetaldehyde, ethane, ethanol. a) What would be their elution order in gas chromatography (GC)? Justify. b) Would derivatization be necessary to analyze these compounds by GC? Justify.

QUESTION 2: Suggest a derivatization reaction for fatty acids being analyzed by GC with a flame ionization detector. Justify your choice and write a chemical equation if appropriate.

QUESTION 3: What is the difference between the total ion current and a selected ion current in gas chromatographymass spectrometry (GC/MS)?

QUESTION 4: Given the four compounds shown here

Which mode of HPLC would you prefer to use for their complete separation, and what would be their elution order? Justify and mention the types of mobile and stationary phases used.

QUESTION 5: What are the differences between a UV absorption spectrum and an excitation spectrum obtained using a spectrofluorimeter?

QUESTION 6: What would the positive mode electrospray ionization spectrum of a protein molecule of MW 1500 look like? In other words, determine m/z values for ions likely to be observed.

QUESTION 7: Two amino acids, serine (pI = 5.68) and tryptophan (pI = 5.89), are to be separated by cation exchange chromatography on beads coated with sulfonic acid groups (pKa = -2). If the mobile phase is at pH 4, which amino acid forms the stronger interaction with the beads (and will elute second)? Justify.

QUESTION 8: Dry beads sold for size exclusion chromatography occupy 0.8 mL per gram. When mixed with solvent, they occupy 1.5 x as much volume. a) Calculate Vm for a 50 mL column. b) Can you derive the V0 value from this calculation?

QUESTION 9: What is the significance of determining Kd during an affinity chromatographic experiment?

QUESTION 10: a) Why is fluorescence detection more sensitive than UV-absorbance for HPLC experiments? b) Name two major disadvantages of fluorescence detection vs. UV-absorption.

QUESTION 11: What are the main differences between a quadrupole and an ion trap m/z analyzer?

QUESTION 12: Name four parameters that one could change to speed up the elution of compounds in HPLC and justify your choices.

QUESTION 13: For the compound methyl-ethyl ketone, draw an electron impact ionization mass spectrum, with molecular ion and main fragments.

QUESTION 14: Suggest a fluorescence label for the analysis of monosaccharides by HPLC. Comment on the advantages of using this method for the analysis of multiple monosaccharides in a mixture.

QUESTION 15: Explain the principle of size exclusion chromatography....