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Instrumental Analysis I > Exam #1 > Flashcards

Exam #1 Flashcards

1
Q

Define Analyte

A
  • chemical to be measured
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2
Q

Define Matrix

A
  • non-analyte components of a sample
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3
Q

Define Qualitative Analysis

A
  • information regarding the identity of the analyte
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4
Q

Define Quantitative Analysis

A
  • numerical information regarding the relative concentration of the analyte in a sample
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5
Q

What are the two types of analytical methods?

A
  • classical

- instrumental

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6
Q

Describe the classical analytical method

A
  • separation by precipitation, extraction, distillation

- gravimetric and titrimetric analysis

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7
Q

Describe the instrumental analytical method

A
  • separation by chromatography and electrophoresis

- analysis involving electromagnetic radiation, electrical properties, mass to charge ratio

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8
Q

What is the broad example on how analytical instruments work?

A
  • the stimulus elicits a response from the analyte in the sample
  • use of a narrow band of visible light to measure extent of absorption
  • the stimulus exerts energy source towards the object under study and the response is the analytical information
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9
Q

Define Data Domains

A
  • methods of encoding chemical and physical characteristics
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10
Q

What kind of domains are classical?

A
  • nonelectrical domains
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11
Q

What kind of domains are instrumental?

A
  • electrical domains
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12
Q

Define Time Domain

A
  • information is stored as time relationship of signal fluctuations (frequency is related to intensity)
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13
Q

Define Analog Signals

A
  • information is encoded as the magnitude of an electrical quantity (ex) voltage, current
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14
Q

Define Digital Signals

A
  • information is encoded in a 2-level scheme as binary numbers; serial data & amp; parallel data
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15
Q

Define Serial Data

A
  • a type of digital signal

- encoded on a single transmission line

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16
Q

Define Parallel Data

A
  • a type of digital signal

- all data encoded simultaneously

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17
Q

Define Time Domain

A
  • information is stored in the time domain as the time relationships of signal fluctuations
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18
Q

What is a Detector?

A
  • device that records a change to an environmental variable (light)
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19
Q

What is a Detection System?

A
  • entire assemblies that record these changes
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20
Q

What is a Transducer?

A
  • converts information in nonelectrical domain to electrical domain and vice versa
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21
Q

What is a Sensor?

A
  • analytical devices that monitor specific chemicals continuously and reversibly
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22
Q

What are the 3 types of Instrumental Calibration?

A
  • external standard calibration
  • standard addition
  • internal standard method
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23
Q

What is External Standard Calibration?

A
  • standards containing the analyte are prepared
  • calibration curve of response versus standard concentration used to determine unknown concentrations
  • use method of least squares to obtain the equation of the line
    measure response (y) of unknown to calculate the concentration (x)
  • works when no interferences from matrix components in sample
  • a great method when a matrix is out of the equation
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24
Q

What is Standard Addition?

A
  • standards are added to sample aliquots
  • the graph is used for calibration
  • sample is spiked with different volumes of standard
  • corrects for some matrix effects
    unknown concentration cx=bcs/mVx where b=intercept and m=slope, cs is the concentration of the standard and Vx is the volume of the unknown
  • needs lots of each sample in order to analyze
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25
Q

What is Internal Standard method?

A
  • the internal standard is added to all samples, blanks calibration standards
  • calibration involves ratio of analyte to internal standard signal as a function of concentration
  • may correct for instrumental and method variations
  • may be difficult to find an internal standard
  • should be as similar to analyte as possible but must be distinguishable
  • must not be in the sample
  • considered the best method
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26
Q

Define Spectroscopy

A
  • interaction of electromagnetic radiation and matter
27
Q

Define Spectrometry

A
  • measurement of the intensity of radiation with a photoelectric transducer
  • includes visible, ultraviolet, infrared, microwave, radio-frequency, gamma rays, and x-rays (entire range of electromagnetic wave)
28
Q

What are the Superpositions of Waves?

A
  • when 2 or more waves traverse the same space, they can add to become bigger or interfere to become smaller
  • when 2 waves are completely in phase, maximum constructive interference occurs
  • when 2 waves are completely out of phase, maximum destructive interference occurs
29
Q

What is Diffraction?

A
  • a parallel beam of monochromatic radiation is bent following passage through a narrow opening
  • allows separation of light due to constructive interference at specific wavelengths
30
Q

Define photons

A
  • a stream of discrete particles

- light

31
Q

Define Quantized

A
  • atoms, ions, and molecules existing only in certain discrete states characterized by specific amounts of energy
32
Q

What are the Electronic Energy States?

A
  • atoms, ions and molecules possess quantized energy states from the motion of electrons
33
Q

What are the 3 types of energy states

A
  • slectronic energy states
  • vibrational states
  • rotational states
34
Q

Define Vibrational States

A
  • occurs when atoms in a molecule periodic motion while the molecule as a whole has constant transitional and rotational motion
35
Q

Define Rotational States

A
  • the rotation of molecules around their centers of mass
36
Q

What is Sensitivity?

A
  • the ability of an analytical technique to distinguish between small differences in concentration
  • there are 2 types: calibration sensitivity and analytical sensitivity
37
Q

Define Calibration Sensitivity (m)

A
  • the slope of the calibration curve at the concentration of interest
38
Q

Define Analytical Sensitivity (gamma)

A
  • includes measurement precision gamma=m/ss where ss is the standard deviation of the measurement and gamma is insensitive to amplification factors and measurement units
39
Q

What is Limit of Detection?

A
  • LOD

- minimum concentration detectable at a known concentration level

40
Q

What is Linear Dynamic Range?

A
  • LDR
  • extends from lowest concentration at which quantitative measurements may be made to the concentration departure from linearity occurs by 5%
41
Q

What is Selectivity?

A
  • the degree to which a method is free from interferences by the sample matrix
42
Q

Define Photometer

A
  • source, filter and detector
43
Q

Define Spectrometer

A
  • measures intensity of radiation as a function of wavelength
44
Q

Define Spectrophotometer

A
  • a spectrometer that allows the determination of the ratios of two beams for absorption spectrometry
45
Q

Define Spectrofluorometer

A
  • spectrophotometer used for fluorescence measurements
46
Q

Define Coherent Radiation

A
  • radiation that is made up of wave trains having identical frequencies or sets of frequencies and phase relationships that are constant with time
47
Q

What is Dispersion of a Transparent Substance?

A
  • the variation in refractive index as a function of wavelength
48
Q

What is Anomalous Dispersion?

A
  • the sharp change in refractive index of a substance in a wavelength region where absorption is occuring
49
Q

What is the Work Function of a Substance?

A
  • a constant that measures the energy required to remove an electron from the surface of the substance
50
Q

Define the Photoelectric Effect

A
  • involves the emission of electrons from the surface of a substance brought about by a beam of radiation
51
Q

What is the Ground State of a Molecule?

A
  • the lowest energy state
52
Q

Define Electronic Excitation

A
  • the process by which electrons in a substance are promoted from their ground state to higher electronic states by absorption of energy
53
Q

Define Blackbody Radiation

A
  • the continuum radiation emitted by a solid when it is heated
54
Q

Define Fluorescence

A
  • a type of emission which is brought about by irradiating atoms, ions, or molecules with electromagnetic radiation
55
Q

Define Phosphorescence

A
  • a type of emission brought by irradiating a molecular system with electromagnetic radiatio
56
Q

Define Resonance Flurescence

A
  • a type of emission in which the radiation produced is of the same wavelength as that used to excite the fluorescence
57
Q

Define Photon

A
  • a bundle or particle or radiant energy with a magnitude of hv, where h is Planck’s constant and v is the frequency of the radiation
58
Q

Define Absorptivity

A
  • defined by the equation a=A/bc where A is the absorbance of a medium contained in a cell length of b and concentration c
  • the path length b is expressed in cm
  • the concentration is expressed in units such as g/L
59
Q

What is the Wavenumber?

A
  • the reciprocal of the wavelength in centimeters
60
Q

What is Relaxation?

A
  • the process whereby an excited species loses energy and returns to a lower energy state
61
Q

What is the Stokes Shift?

A
  • the difference in wavelength between the incident radiation and the wavelength of fluorescence or scattering
62
Q

What is a Spectroscope?

A
  • an optical instrument for visual identification of spectra

- a device with an entrance slit, dispersing element, and an eyepiece that can be moved along the focal plane

63
Q

What is a Spectrograph?

A
  • a device with an entrance slit, a dispersing element, and a large aperture ext that allows a wide range of wavelengths to strike a multi channel detector in the focal plane
64
Q

What is a Spectrophotometer?

A
  • an instrument with monochromator or polychromator and photodetector arranged to allow the ratio of two beams to be obtained

Instrumental Analysis I (1 decks)

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