Mock Exam 2 Flashcards
the log of the ratio of the irradiance striking the sample and the radiant power emerging from the other side
absorbance
the fraction of incident radiation that passes through a sample
transmittance
process in which a molecule emits a photon due to transition between states of the same spin multiplicity
fluorescence
emission of light during a transition between states of different spin multiplicity (eq triplet to singlet)
phosphorescence
a graph of luminescence intensity versus luminescence wavelength obtained with a fixed excitation wavelength
emission spectrum
a graph of luminescence versus excitation frequency or wavelength
excitation spectrum
any state of an atom or molecule with more than the minimum possible energy
excited state
state of an atom or molecule with the minimum possible energy
ground state
electronic state in which all electron spins are paired
singlet
an electronic state in which there are two unpaired electrons t
triplet
process in which emission from an excited molecule is decreased by energy transfer to another molecule
quenching
In luminescence, a decrease in emission intensity due to absorption of excitation or emission irradiance by analyte molecules
self-absorption
the range of wavelengths or frequencies of an absorption or emission band, typically measured at a height equal to half of the peak height
bandwidth
the application of numerical algorithms to data to reduce noise
digital smoothing
in atomic absorption, periodic blocking of the beam allows a distinction to be made between light from the source and light from the flame
beam chopping
improvement of signal by averaging successive scans
signal averaging
relative population of two states at thermal equilibrium related to the degeneracy of the ground and excited states, the energy gap between them, the temp, and a constant
boltzman distribution
a molecule moving toward a source of radiation experiences a higher frequency than one moving away from the source
doppler effect
in spectroscopy, line broadening due to collisions between molecules
pressure broadening
most intense peak in a mass spectrum
base peak
integer mass of the species with the most abundant isotope of each of the constituent atoms
nominal mass
in mass spectrometry, an ion that has not lost or gained any atoms during ionization
molecular ion
process of breaking a liquid into a mist of fine droplets
nebulization
a suspension of very small liquid or solid particles in air or gas
aerosol
Which does not result in deviations from linearity in a Beer’s law plot of absorbance versus concentration? (Check all that apply):
_light losses at the cell interface
_a wide bandwidth relative to the width of the absorption band
_stray radiation
_equilibrium between different forms of the analyte
_all are sources of nonlinearity
light losses at the cell interface
When a molecule absorbs an infrared photon, which of the molecular transitions is observed? (Check best answer): _electronic _vibrational _rotational _nuclear spin
vibrational
When a molecule absorbs UV radiation which molecular transition is observed?
electronic
When a molecule absorbs a microwave, which molecular transition is observed?
rotational
when a molecule absorbs an X-ray, which molecular transition is observed?
nuclear spin
- In comparing fluorescence spectroscopy to UV‑Vis absorption spectroscopy, which of the statements is true? (Check the best answer.)
_____ Fluorescence measurements are more precise and less noisy because only the intensity of the emitted light is measured.
_____ Fluorescence measurements do not suffer deviations from linearity like absorbance measurements do.
_____ Fluorescence measurements have better detection limits because at low concentrations a low intensity emission signal is being measured against a low intensity background signal.
_____ Fluorescence instruments are less expensive than absorption measurements.
Fluorescence measurements have better detection limits because at low concentrations a low intensity emission signal is being measured against a low intensity background signal.
- Classify the phrases based on whether they describe fluorescence or phosphorescence. (Label each line F or P as appropriate.)______ S1 to S0______ lower energy______ shorter wavelength
(F) S1 to S0
(P) lower energy
(F) shorter wavelength
Classify the phrases based on whether they describe fluorescence or phosphorescence. (Label each line F or P as appropriate.)
___ triplet to singlet
___ higher energy
___ longer wavelength
(P) triplet to singlet
(F) higher energy
(P) longer wavelength
- If I am developing a LC/MS method for polar molecules and want to maximize production of the molecular ion (that is minimize fragmentation), what type of ionization would I use? (Check the best answer.)
______ Electrospray Ionization
______ Electrospray Ionization with Collision Induced Dissociation
______ Electron Impact Ionization
______ Matrix Assisted Laser Desorption/Ionization (MALDI)
______ Direct Analysis in Real Time (DART)
electrospray ionization
Causes fragmentation because it has a low vacuum with N2 or helium
Electrospray ionization with collision induced dissociation
used in GC/MS where electrons interact with solid or gas phase atoms or molecules to produce ions
electron impact ionization
Can’t be used with LC/MS; used with polymer and biological samples; is a soft ionization that involves a laser striking a matrix of small molecules to make the analyte molecules into the gas phase without fragmenting or decomposing them.
Matrix assisted laser desorption/ionization (MALDI)
can’t be used with LC/MS; like MALDI but with atm pressure; an ion source that produces electronically or vibronically excited-state species from gases such as helium, argon, or nitrogen that ionize atmospheric molecules or dopant molecules; Analytes with low ionization energy may be ionized directly.
Direct Analysis in Real Time (DART)
If I would like to use a mass spectrometry with my chromatography technique and I’d like a relatively inexpensive mass spectrometer with unit resolution, I’d likely chose which mass spectrometer? (Check the best answer.)
______ Time of Flight (TOF)
______ Triple Quadrupole (QqQ)
______ Transmission Quadrupole – collision cell - Time of Flight (Q-TOF)
______ Transmission Quadrupole
______ Orbitrap
transmission quadrupole
ions of different masses accelerated through the same electric field have different velocities. The lighter ions move faster than the heavier ions. This finds the mass to charge ratio by measuring the time that each group of ions requires to travel a fixed distance to the detector
gives higher resolution than unit resolution
time of flight mass spectrometer
a tandem mass spectrometer consisting of two quadrupole mass analyzers in series, with a (non-mass-resolving) radio frequency (RF)–only quadrupole between them to act as a cell for collision-induced dissociation.
can get a low detection limit
Triple Quadrupole (QgQ) mass spectrometer
a mass spectrometer that separates ions by passing them between four parallel metallic rods to which are applied direct current and oscillating electric fields, Resonant ions with the right m/z ratio pass through the chamber to the detector while non resonant ions are deflected into rods and are lost
expensive
transmission quadrupole
a device that traps ions in stable orbits around a central cathode; ions oscillate from one end of the trap to the other, inducing image currents in the outer electrodes; fourier image analysis gives m/z for oscillating ions
expensive
orbitrap
If I have decreased signal for the neutral alkali metal that I am trying to measure by atomic spectroscopy due to its low ionization potential, what kind of interference is it? (Check the best answer.) \_\_\_\_\_\_ Spectral Interference \_\_\_\_\_\_ Physical Interference \_\_\_\_\_\_ Chemical Interference \_\_\_\_\_\_ Ionization Interference
ionization interference
in atomic spectroscopy, any optical process that affects light intensity at the analytical wavelength. Created by substance that absorb, scatter, or emit light of the analytical wavelength
spectral interference
interference in atomic spectroscopy cause by any component of the sample that alters sample transport or nebulization, For example differences in viscosity or density of samples due to their matrix
physical interference
in atomic spectroscopy, any chemical reaction that alters the efficiency of atomization
chemical interference
If I wanted a light source that gives a narrow bandwidth of light without the need of filters, which of the following would be the best choice? (Check the best answer.)
______ A blackbody source like a globar
______ An arc source like a deuterium lamp
______ A line source like a mercury vapor lamp
______ A laser
a laser
A laser works by light amplification through stimulated emission. The amplification occurs in the optical cavity created by what objects?
mirrors
Atomic spectroscopy must provide background correction to distinguish analyte signal from absorption, emission, and optical scattering of the sample matrix, the flame, red-hot graphite furnace, or plasma. Which of the following is the name of the technique whereby a strong magnetic field, applied parallel to the light path through a furnace, is pulsed on and off to create alternating periods of signal due sample and background and signal due to the background alone? (Choose the best answer.)
\_\_\_\_\_\_ subtract adjacent pixels of CID display \_\_\_\_\_\_ beam chopping \_\_\_\_\_\_ deuterium lamp \_\_\_\_\_\_ Zeeman effect
zeeman effect
the effect of splitting of a spectral line into several components in the presence of a static magnetic field
zeeman effect
a low-pressure gas-discharge light source often used in spectroscopy when a continuous spectrum in the ultraviolet region is needed.
deuterium lamp
If you want to do quantitative atomic spectroscopy of many analytes at the lowest possible detection limits, what technique should you choose? (Choose the best answer.)
\_\_\_\_\_\_ ICP-MS \_\_\_\_\_\_ Graphite Furnace AA \_\_\_\_\_\_ X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy \_\_\_\_\_\_ ICP-Optical Emission \_\_\_\_\_\_ Atomic Fluorescence \_\_\_\_\_\_ Flame AA \_\_\_\_\_\_ Laser Ablation – ICP
ICP-MS
If you want to do quantitative atomic spectroscopy of FEW analytes at the lowest possible detection limits, what technique should you choose? (Choose the best answer.)
\_\_\_\_\_\_ ICP-MS \_\_\_\_\_\_ Graphite Furnace AA \_\_\_\_\_\_ X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy \_\_\_\_\_\_ ICP-Optical Emission \_\_\_\_\_\_ Atomic Fluorescence \_\_\_\_\_\_ Flame AA \_\_\_\_\_\_ Laser Ablation – ICP
Atomic fluorescence
If you want to do quantitative atomic spectroscopy of many analytes as low as 100s ppt, what technique should you choose? (Choose the best answer.)
\_\_\_\_\_\_ ICP-MS \_\_\_\_\_\_ Graphite Furnace AA \_\_\_\_\_\_ X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy \_\_\_\_\_\_ ICP-Optical Emission \_\_\_\_\_\_ Atomic Fluorescence \_\_\_\_\_\_ Flame AA \_\_\_\_\_\_ Laser Ablation – ICP
ICP-Optical Emission
If you want to do quantitative atomic spectroscopy of Few analytes as low as 100s ppt, what technique should you choose? (Choose the best answer.)
\_\_\_\_\_\_ ICP-MS \_\_\_\_\_\_ Graphite Furnace AA \_\_\_\_\_\_ X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy \_\_\_\_\_\_ ICP-Optical Emission \_\_\_\_\_\_ Atomic Fluorescence \_\_\_\_\_\_ Flame AA \_\_\_\_\_\_ Laser Ablation – ICP
Graphite furnace AA
If you want to do quantitative atomic spectroscopy of FEW analytes as low as ppb detection limits, what technique should you choose? (Choose the best answer.)
\_\_\_\_\_\_ ICP-MS \_\_\_\_\_\_ Graphite Furnace AA \_\_\_\_\_\_ X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy \_\_\_\_\_\_ ICP-Optical Emission \_\_\_\_\_\_ Atomic Fluorescence \_\_\_\_\_\_ Flame AA \_\_\_\_\_\_ Laser Ablation – ICP
Flame AA
If you want to do qualitative atomic spectroscopy of a solid sample with many analytes at % levels most economically, what technique should you choose? (Choose the best answer.)
\_\_\_\_\_\_ ICP-MS \_\_\_\_\_\_ Graphite Furnace AA \_\_\_\_\_\_ X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy \_\_\_\_\_\_ ICP-Optical Emission \_\_\_\_\_\_ Atomic Fluorescence \_\_\_\_\_\_ Flame AA \_\_\_\_\_\_ Laser Ablation – ICP
X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy
If you want to do qualitative atomic spectroscopy of a solid sample with many analytes at as low as ppb levels most economically, what technique should you choose? (Choose the best answer.)
\_\_\_\_\_\_ ICP-MS \_\_\_\_\_\_ Graphite Furnace AA \_\_\_\_\_\_ X-Ray Fluorescence or Laser Induced Breakdown Spectroscopy \_\_\_\_\_\_ ICP-Optical Emission \_\_\_\_\_\_ Atomic Fluorescence \_\_\_\_\_\_ Flame AA \_\_\_\_\_\_ Laser Ablation – ICP
Laser Ablation – ICP
Describe how ELISA (enzyme‑linked immunosorbent assay) is used to quantify the amount of analyte in a sample by placing the steps in order from first (1) to last (7).
______ A nonfluorescent reactant is introduced
______ The surface is washed to remove unbound sample
______ An antibody, specific for the analyte, is bound to a polymer support
______ The surface is washed to remove unbound enzyme-linked antibody.
______ Sample containing analyte is incubated with the polymer-bound antibody
______ The enzyme converts the nonfluorescent reactant into a fluorescent product
______ The antibody-analyte complex is incubated with an enzyme-linked antibody, specific for a different region of the analyte.
6______ A nonfluorescent reactant is introduced
3______ The surface is washed to remove unbound sample
1______ An antibody, specific for the analyte, is bound to a polymer support
5______ The surface is washed to remove unbound enzyme-linked antibody.
2______ Sample containing analyte is incubated with the polymer-bound antibody
7______ The enzyme converts the nonfluorescent reactant into a fluorescent product
4______ The antibody-analyte complex is incubated with an enzyme-linked antibody,
specific for a different region of the analyte.
