Mock Exam 2 Flashcards by Alyssa Austin

the log of the ratio of the irradiance striking the sample and the radiant power emerging from the other side

absorbance

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the fraction of incident radiation that passes through a sample

transmittance

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process in which a molecule emits a photon due to transition between states of the same spin multiplicity

fluorescence

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emission of light during a transition between states of different spin multiplicity (eq triplet to singlet)

phosphorescence

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a graph of luminescence intensity versus luminescence wavelength obtained with a fixed excitation wavelength

emission spectrum

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a graph of luminescence versus excitation frequency or wavelength

excitation spectrum

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any state of an atom or molecule with more than the minimum possible energy

excited state

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state of an atom or molecule with the minimum possible energy

ground state

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electronic state in which all electron spins are paired

singlet

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an electronic state in which there are two unpaired electrons t

triplet

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process in which emission from an excited molecule is decreased by energy transfer to another molecule

quenching

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In luminescence, a decrease in emission intensity due to absorption of excitation or emission irradiance by analyte molecules

self-absorption

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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

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the application of numerical algorithms to data to reduce noise

digital smoothing

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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

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improvement of signal by averaging successive scans

signal averaging

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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

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a molecule moving toward a source of radiation experiences a higher frequency than one moving away from the source

doppler effect

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in spectroscopy, line broadening due to collisions between molecules

pressure broadening

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most intense peak in a mass spectrum

base peak

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integer mass of the species with the most abundant isotope of each of the constituent atoms

nominal mass

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in mass spectrometry, an ion that has not lost or gained any atoms during ionization

molecular ion

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process of breaking a liquid into a mist of fine droplets

nebulization

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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

14. 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.

15. 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

16. 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.