Exam #1 Flashcards
(64 cards)
1
Q
Define Analyte
A
- chemical to be measured
2
Q
Define Matrix
A
- non-analyte components of a sample
3
Q
Define Qualitative Analysis
A
- information regarding the identity of the analyte
4
Q
Define Quantitative Analysis
A
- numerical information regarding the relative concentration of the analyte in a sample
5
Q
What are the two types of analytical methods?
A
- classical
- instrumental
6
Q
Describe the classical analytical method
A
- separation by precipitation, extraction, distillation
- gravimetric and titrimetric analysis
7
Q
Describe the instrumental analytical method
A
- separation by chromatography and electrophoresis
- analysis involving electromagnetic radiation, electrical properties, mass to charge ratio
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
9
Q
Define Data Domains
A
- methods of encoding chemical and physical characteristics
10
Q
What kind of domains are classical?
A
- nonelectrical domains
11
Q
What kind of domains are instrumental?
A
- electrical domains
12
Q
Define Time Domain
A
- information is stored as time relationship of signal fluctuations (frequency is related to intensity)
13
Q
Define Analog Signals
A
- information is encoded as the magnitude of an electrical quantity (ex) voltage, current
14
Q
Define Digital Signals
A
- information is encoded in a 2-level scheme as binary numbers; serial data & amp; parallel data
15
Q
Define Serial Data
A
- a type of digital signal
- encoded on a single transmission line
16
Q
Define Parallel Data
A
- a type of digital signal
- all data encoded simultaneously
17
Q
Define Time Domain
A
- information is stored in the time domain as the time relationships of signal fluctuations
18
Q
What is a Detector?
A
- device that records a change to an environmental variable (light)
19
Q
What is a Detection System?
A
- entire assemblies that record these changes
20
Q
What is a Transducer?
A
- converts information in nonelectrical domain to electrical domain and vice versa
21
Q
What is a Sensor?
A
- analytical devices that monitor specific chemicals continuously and reversibly
22
Q
What are the 3 types of Instrumental Calibration?
A
- external standard calibration
- standard addition
- internal standard method
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
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
25
What is Internal Standard method?
- 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
26
Define Spectroscopy
- interaction of electromagnetic radiation and matter
27
Define Spectrometry
- 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
What are the Superpositions of Waves?
- 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
What is Diffraction?
- 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
Define photons
- a stream of discrete particles
| - light
31
Define Quantized
- atoms, ions, and molecules existing only in certain discrete states characterized by specific amounts of energy
32
What are the Electronic Energy States?
- atoms, ions and molecules possess quantized energy states from the motion of electrons
33
What are the 3 types of energy states
- slectronic energy states
- vibrational states
- rotational states
34
Define Vibrational States
- occurs when atoms in a molecule periodic motion while the molecule as a whole has constant transitional and rotational motion
35
Define Rotational States
- the rotation of molecules around their centers of mass
36
What is Sensitivity?
- the ability of an analytical technique to distinguish between small differences in concentration
- there are 2 types: calibration sensitivity and analytical sensitivity
37
Define Calibration Sensitivity (m)
- the slope of the calibration curve at the concentration of interest
38
Define Analytical Sensitivity (gamma)
- 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
What is Limit of Detection?
- LOD
| - minimum concentration detectable at a known concentration level
40
What is Linear Dynamic Range?
- LDR
- extends from lowest concentration at which quantitative measurements may be made to the concentration departure from linearity occurs by 5%
41
What is Selectivity?
- the degree to which a method is free from interferences by the sample matrix
42
Define Photometer
- source, filter and detector
43
Define Spectrometer
- measures intensity of radiation as a function of wavelength
44
Define Spectrophotometer
- a spectrometer that allows the determination of the ratios of two beams for absorption spectrometry
45
Define Spectrofluorometer
- spectrophotometer used for fluorescence measurements
46
Define Coherent Radiation
- radiation that is made up of wave trains having identical frequencies or sets of frequencies and phase relationships that are constant with time
47
What is Dispersion of a Transparent Substance?
- the variation in refractive index as a function of wavelength
48
What is Anomalous Dispersion?
- the sharp change in refractive index of a substance in a wavelength region where absorption is occuring
49
What is the Work Function of a Substance?
- a constant that measures the energy required to remove an electron from the surface of the substance
50
Define the Photoelectric Effect
- involves the emission of electrons from the surface of a substance brought about by a beam of radiation
51
What is the Ground State of a Molecule?
- the lowest energy state
52
Define Electronic Excitation
- the process by which electrons in a substance are promoted from their ground state to higher electronic states by absorption of energy
53
Define Blackbody Radiation
- the continuum radiation emitted by a solid when it is heated
54
Define Fluorescence
- a type of emission which is brought about by irradiating atoms, ions, or molecules with electromagnetic radiation
55
Define Phosphorescence
- a type of emission brought by irradiating a molecular system with electromagnetic radiatio
56
Define Resonance Flurescence
- a type of emission in which the radiation produced is of the same wavelength as that used to excite the fluorescence
57
Define Photon
- 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
Define Absorptivity
- 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
What is the Wavenumber?
- the reciprocal of the wavelength in centimeters
60
What is Relaxation?
- the process whereby an excited species loses energy and returns to a lower energy state
61
What is the Stokes Shift?
- the difference in wavelength between the incident radiation and the wavelength of fluorescence or scattering
62
What is a Spectroscope?
- 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
What is a Spectrograph?
- 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
What is a Spectrophotometer?
- an instrument with monochromator or polychromator and photodetector arranged to allow the ratio of two beams to be obtained
