final exam

Question 1

sensitivity

Answer 1

the magnitude of the change in signal resulting from an incremental change in analyte concentration
the higher the sensitivity, the lower the limit of detection

Question 2

limit of detection (LOD)

Answer 2

the lowest concentration of a compound that may be statistically differentiated from the background noise

Question 3

selectivity

Answer 3

the ability of the method to discriminate between two different atoms/ions/compounds

Question 4

what is spectroscopy

Answer 4

it typically involves the measurement of the interaction of matter and radiation
radiation may be in the form of light, electrons, or magnetic fields

Question 5

what does Beer’s Law quantitate

Answer 5

absorbance (in spectrophotometry)

Question 6

advantages of absorbance spectroscopy

Answer 6

• spectral data possible (absorption spectra are characteristic)
• technology widely available
• may be used as detection scheme in chromatography (improving selectivity)
• multiple species may absorb at a given wavelength (useful if epsilon(lambda) is know for multiple lambda for each species in the particular matrix in question)

Question 7

limitations of absorbance spectroscopy

Answer 7

• epsilon is environmentally sensitive (pH, solvent, etc.) so matrix effects may be problematic
• sensitivity typically limited (not great for trace analysis)
• linearity of Beer’s Law limited (often to < 0.01 M)

Question 8

what does UV absorbance spectroscopy involve

Answer 8

promotion of electrons to higher energy levels

Question 9

what does IR absorption spectroscopy involves

Answer 9

it excites vibrational energy levels of the absorbing molecule (bandes de Maude)

Question 10

group frequency region

Answer 10

contains spectral features corresponding to particular functional groups

Question 11

fingerprint region

Answer 11

contains features arising from the characteristic combination of functional units in the molecule

Question 12

what is vapour-phase IR spectroscopy used for

Answer 12

measurement of breath ethanol concentration

Question 13

advantages and limitations of IR spectroscopy

Answer 13

• compounds have characteristic IR spectra (ID easier)
• IR is a form of absorption so Beer’s law is possible to a certain extent
• acuracy and precision may be lower than that encountered with UV-Vis techniques

Question 14

basics of atomic spectroscopy

Answer 14

• in some cases, knowledge of the relative elemental composition is required
• flame atomic absorption spectroscopy : solutions converted to aerosols and then introduced into a flame

Question 15

fluorescence

Answer 15

occurs when an electron is excited through photon absorption, and the excited state energy is dissipated through re-emission of a photon

Question 16

advantages and limitations of fluorescence spectroscopy

Answer 16

• significantly more sensitive than absorptive methods
• selectivity can be enhanced by judicious choice of both lambda exc and lambda em
• may require labeling when used as detection scheme in chromatography, electrophoresis
• environmentally sensitive

Question 17

applications of fluorescence spectroscopy

Answer 17

detection of semen stains on fabric

Question 18

chromatography

Answer 18

separation of constituents in a mixture through differential interaction between two phases - a mobile phase and a stationnary phase

Question 19

resolution

Answer 19

ability of a method to separate two constituents (manifested as the extent of peak overlap)

Question 20

what is electrophoresis used for

Answer 20

inorganic ions, amino acids, catecholamines, drugs, proteins and nucleic acids

Question 21

mechanism of amphetamin / methamphetamine

Answer 21

increasing the concentration of norepinephrine and dopamine in the synapse, through inhibition of reuptake and neurotransmitter release

Question 22

MDMA (ecstasy)

Answer 22

synthetic drug that promotes release and inhibits reuptake of serotonin in nerve synapses

Question 23

stimulants presented in class

Answer 23

• amphetamine / methamphetamine
• MDMA
• cocaine

Question 24

cocaine mechanism

Answer 24

inhibition of dopamine reuptake

Question 25

depressants presented in class

Answer 25

• alcohol
• opioids
• benzodiazepines

Question 26

hallucinogens talked about in class

Answer 26

• cannabis / THC

- LSD

Question 27

marquis test

Answer 27

• purple with opioids (heroin, morphine, etc.)

- orange-brown with meth / amph

Question 28

Duquenois-Levine test

Answer 28

purple with cannabinoids

Question 29

Van Urk test

Answer 29

blue-purple with LSD

Question 30

Scott test

Answer 30

cocaine

Question 31

conduction

Answer 31

heat transfer to another body or within a body by direct contact, “molecular propagation”

Question 32

convection

Answer 32

heat transfer by circulation within a medium

Question 33

radiation

Answer 33

electromagnetic energy

Question 34

requirements for spontaneous combustion

Answer 34

• a process that slowly releases heat
• insulation of the substrate so that heat is retained and can accumulate
• availability of air for combustion

Question 35

possible sources of ignition

Answer 35

thermal, electrical, mechanical, chemical

Question 36

major detectable elements in gunpowder (gunshot residue)

Answer 36

• lead (Pb)
• barium (Ba)
• antimony (Sb)

Question 37

modified griess test

Answer 37

specific for nitrates found in partially burned gunpowder

Question 38

sodium rhodizonate test

Answer 38

specific for lead

Question 39

medullary index

Answer 39

diameter of the medulla divided by the diameter of the hair shaft