Questions

CH420 / CH620 Forensic Chemistry Part 2 Exam—Due Wednesday December 7, 2020

100 points possible Name _____________________________

Multiple Choice. Select the BEST answer for each question (3 points each). Enter your answers in

the Moodle Quiz.

1. Headspace sampling takes advantage of what type of equilibrium?

A. liquid-liquid equilibrium

B. liquid-solid equilibrium

C. liquid-vapor equilibrium

D. hypostatic equilibrium

2. Which of the following can affect the affinity of an analyte for a particular phase?

A. volatility

B. polarity

C. hydrogen-bonding interactions

D. all of these

3. Which of the following is a synonym for the term hydrophilic?

A. hydrophobic

B. lipophilic

C. hypsochromic

D. lipophobic

4. Which of the following can be used to manipulate a partition equilibrium?

A. pH

B. molecular mass

C. boiling point

D. Duck® tape

5. The structures of naproxen (pKa = 4.2) and codeine (pKa = 8.2) are given below. A liquid-liquid

extraction of a mixture of naproxen sodium and codeine hydrochloride that would partition naproxen

into the aqueous layer and codeine into the organic layer would require an aqueous layer pH of

A. 10.2

B. 2.2

C. 6.2

D. 4.2

6. Which of the following is not a qualitative identification method discussed in this class?

A. Fourier-transform infrared spectroscopy

B. aptamer binding assay

C. thin-layer chromatography

D. time of flight mass spectrometry

7. Which of the following is not an acceptable confirmatory test under SWGDRUG guidelines?

A. Fourier transform infrared spectroscopy (FTIR)

B. Enzyme-linked immunosorbent assay (ELISA)

C. Mass spectrometry (MS)

D. Nuclear magnetic resonance spectroscopy (NMR)

8. Which of the following techniques is considered to be a non-destructive technique?

A. Gas chromatography-mass spectrometry (GC-MS)

B. qualitative color tests

C. Fourier transform infrared spectroscopy (FTIR)

D. Enzyme multiplied immunoassay technique (EMIT)

9. Heroin is a basic drug with a pKa of 7.95. At which pH will heroin’s lipid solubility be greatest?

A. 9.95

B. 7.95

C. 7.0

D. 5.95

10. The generic equation representing EI mass spectrometric ionization is best represented by?

A. A+ + e- → A

B. A + B+ → A+ + B

C. E = mc2

D. A + e- → A+ + 2e-

11. Which of the following discriminations can FTIR NOT make?

A. the salt form versus the free base form of a basic drug

B. the R- versus the S- enantiomer of a drug molecule

C. the R,S- versus the S,S- diastereomers of a drug molecule

D. the bromide salt versus the citrate salt of a basic drug

12. Which of the following bonds has highest stretching frequency in the IR?

A. C-C

B. C=C

C. C=O

D. O-H

13. Which of the following is NOT an advantage of ATR over transmittance for FTIR sampling?

A. easy sample preparation

B. improved signal to noise ratio (S/N)

C. eliminates ion exchange problems with salts of basic drugs

D. variety of items that can be sampled

14. The mass of an analyte is given in the mass spectrum by its

A. base peak.

B. bae peak.

C. parent ion peak.

D. molecular ion peak.

15. For an acidic compound, which of the following general extraction approaches is correct?

A. Lowering the pH at least two units below the pKa will render the compound hydrophilic.

B. Lowering the pH at least two units below the pKa will render the compound lipophobic.

C. Lowering the pH at least two units below the pKa will render the compound water soluble.

D. Lowering the pH at least two units below the pKa will render the compound organic soluble.

16. Which of the following is an important consideration when designing an acid-base extraction

protocol for an amphoteric compound?

A. the mass to charge ratio of the compound (m/z)

B. the stretching frequency of the compound

C. the volatility of the compound

D. the isoelectric point of the compound

17. Which of the following instruments is most appropriate for confirmatory qualitative organic

analysis?

A. Fourier transform infrared spectroscopy (FTIR)

B. Atomic emission spectroscopy (OES or AES)

C. Atomic absorption spectroscopy (AAS)

D. Gas chromatography (GC)

18. Which of the following instruments is most appropriate for separation and analysis of a mixture

of compounds in a biological matrix?

A. High performance liquid chromatography (HPLC)

B. Gas chromatography (GC)

C. Fourier transform infrared spectroscopy (FTIR)

D. Enzyme-linked immunosorbent assay (ELISA)

19. Which of the following techniques employs the least energetic electromagnetic radiation?

A. visible spectroscopy

B. near infrared spectroscopy

C. far infrared spectroscopy

D. ultraviolet spectroscopy

20. A compound with a very low Kow is best described as being

A. lipophilic

B. hydrophobic

C. problematic

D. hydrophilic

21. A basic compound has a pKa of 0.3. Which of the following statements is true?

A. The compound will be in its salt form at a pH of 3.

B. The compound is a very weak base.

C. The compound is amphoteric.

D. The compound cannot be extracted into water.

A new class of drugs that has become a problem in recent years is the synthetic cannabinoids, two examples of

which are called JWH-018 and JWH-250 (pictured below), commonly found in a product called “Spice.” Answer

questions 22, 23, 24, and 25 about these two compounds.

22. Which of the following differences would you expect to observe between the FTIR spectra of

JWH-018 and JWH-250?

A. JWH-018 should have a higher C=O stretching frequency than JWH-250.

B. JWH-250 should have a sharp band around 1000 to 1200 cm-1 that JWH-018 should lack.

C. Both A and B.

D. None of these.

JWH-018 JWH-250

23. Which of the following is another difference between the FTIR spectra of JWH-018 and JWH-250?

A. JWH-250 should have a higher C=O stretching frequency than JWH-018.

B. JWH-018 should have a sharp band around 1000 to 1200 cm-1 that JWH-250 should lack.

C. Both A and B.

D. None of these.

24. One way to distinguish the mass spectra of JWH-018 and JWH-250 is by their molecular ion

peaks. Which pair of m/z ratios represents the respective M+ peaks of JWH-018 and JWH-250?

A. 342 and 336

B. 018 and 250

C. 339 and 333

D. 341 and 335

25. While their M+ peaks help to distinguish them, the mass spectra of JWH-018 and JWH-250 have

a very high-abundance peak in common between them. That peak arises from bond cleavage alpha

to the ketone carbonyl, resulting in a common fragment ion for both compounds. What is its m/z

ratio?

A. 270

B. 324

C. 241

D. 214

Another new class of drugs is a group of analogs of the controlled substances cathinone and methcathinone,

most often found in products marketed as “Bath Salts.” These substances, shown below, have chemical

structures very similar to each other and are thus difficult to distinguish by FTIR or GC-MS. Answer questions

26 and 27 about these substances.

26. Despite the difficulty in distinguishing these compounds by FTIR and GC-MS, some of them will

differ significantly in both their mass spectra and their FTIR spectra. Which of the above compounds

will differ from ALL the others by its FTIR spectrum in the region from 3500 to 3300 cm-1, and which

will differ from ALL the others in the region from 1300 to 1000 cm-1?

A. Compound A will differ from ALL others in the 3500 to 3300 cm-1 region; Compound E will differ

from ALL others in the 1300 to 1000 cm-1 region.

B. Compound C will differ from ALL others in the 3500 to 3300 cm-1 region; Compound F will differ

from ALL others in the 1300 to 1000 cm-1 region.

C. Compound B will differ from ALL others in the 3500 to 3300 cm-1 region; Compound C will differ

from ALL others in the 1300 to 1000 cm-1 region.

D. Compound D will differ from ALL others in the 3500 to 3300 cm-1 region; Compound E will

differ from ALL others in the 1300 to 1000 cm-1 region.

A B C

D E F

27. Since FTIR and GC-MS are limited in their power to discriminate among these six compounds,

which of the following methods would be more useful and should allow easy identification of all six

compounds?

A. HPLC with MS detection

B. Atomic absorption spectroscopy

C. Solid-phase extraction followed by ELISA

D. Nuclear magnetic resonance (NMR) spectrometry

28. Which of the following phase equilibria is most relevant in arson analysis?

A. solid-solution equilibrium

B. solution-solution equilibrium

C. solid-gas equilibrium

D. liquid-solution equilibrium

29. Which of the following could not meet SWGDRUG guidelines for drug identification?

A. FTIR spectroscopy and a color test

B. TLC and capillary electrophoresis

C. Raman spectroscopy and melting point

D. GC, liquid chromatography, and fluorescence spectroscopy

30. Cocaine hydrochloride is soluble in which of the following solvents?

A. hexane

B. chloroform

C. diethyl ether

D. none of these

Essay Question (10 points). Expand your answer to additional pages.

31. Choose one of the instrumental methods discussed either in lecture or in the textbook and

describe its operation and function in a way that a layperson (nontechnical) would understand.