Flashcards in Exam 1 Deck (88):
The ability of certain materials to generate an electric charge in response to an applied mechanical stress
Ratio of velocity of light to its velocity traveling thru an object/medium
Noise reduction; recombines reference beam and sample beam after a sample has been split
Light traveling through an object
Velocity of light is lower when.....
Traveling thru something
Travel/movement of waves
Types of Interferences
1. Constructive: increases amplitude
2. Destructive: decreases amplitude; can eliminate a wave completely at its max
Vacuum tube generates microwaves using the interaction between a string of electrons and a magnetic field, moving past a series of open metal cavities
Know the structure of a wave
- wave height
Types of Waves
Shortest wavelength = gamma
Longest wavelength = radio
A. As wavelength decreases, energy increases.
B. The shorter the wavelength, the more power within a wave packet.
C. The more power within a wave packet, the greater the interaction between light and matter.
Electromagnetic radiation can be viewed as.....
The study of the interaction between electromagnetic radiation and matter.
Noise reduction; converts a time domain to a frequency domain
Determines relationship between analytical response and analyte concentration
Data sets are averaged point by point with similar data
Sample that is directly compared to a primary standard; ex. Titration
Using multiple instrument responses to analyze an analyte
Interactions within a sample that can cause extra species in the mixture that are not found in the blank; can cause blanks to become worthless
Difference between a singlet and a triplet state:
A. In an excited singlet state; the electron has the same spin orientation as it had in the ground state (one arrow down, one arrow up)
B. In an excited triplet state; the promoted electron has the same spin orientation as the other electron (both arrows up)
When are singlet and triplet state formed?
When an electron is excited to a higher energy level.
Spectral line associated with absorption or emission of light by an atom, which undergoes a transition that is not allowed by a transition rule.
The Stokes Shift
Difference between positions of the absorption and emission spectra of the same electron transition; occurs when relaxation to a lower energy excited state takes place prior to emission.
Advantages and Disadvantages of Inductively Coupled Plasma
- high limit of detection
- low chemical interference
- stable, reproducible signal
- high maintenance and operating costs
- samples must be dissolved in solution
Advantages and Disadvantages of Flame
- fast, easy to use
- high precision
- large sample quantities needed
- limited to alkali and some earth metals
- issues with refractory elements
Converts characteristic of an analyte into information that can be interpreted
Basic Instrument Design
Stimulus (energy source) —> System under study —> Response
Converts data from one domain to an electrical domain
Types of Blanks:
*used to calibrate instruments*
A. Ideal - identical to sample but withOUT analyte.
B. Solvent - contains the same solvent as the sample.
C. Reagent - contains solvent AND all reagents used in the sample preparation.
Chemicals prepared separately from the standard
Substance added in a constant amount to all samples, blanks, and calibration standards
What does the GC mass spec do?
detects mass to charge ratio; shows isotopes
About the atomic absorbable:
- linear plot obtain due to demonstration of beers law
If data obtained from the AA is NOT linear:
1. You could obtain more points.
2. You have maxed out the detector; dilute your samples
Where are vibrational states found?
Between energy levels
What does atomic X-ray do?
Sees what elements exist within a sample.
What is the most widely used technique?
AA; atomic absorbance
What is the AA used for?
- when looking for a metal and trying to determine concentration
- used in pharmaceutical manufacturing
- it is cheap, fast, and reliable
What is the atomic fluorescence used for?
- lower detection limit than AA
What is X-ray fluorescence used for?
Rocks and minerals, steel/cement industry
Steps in Flame Atomization:
Removal of a solvent
bulk liquid divided into drops
- an increase or decrease in the frequency of sound/light/etc. as the source and observer move towards or away from each other
- if it’s pointing towards you, you see the blue shift (wavelengths are at a higher energy)
- if it’s pointing away from you, you see red shift (wavelengths are at a lower energy)
Changes photon to electron; converting it allows it to be able to be detected by computer.
Difference in energy required to move an electron between bands; difference between HOMO and LUMO
highest occupied molecular orbital
Lowest unoccupied molecular orbital
Factors of band gaps:
C. Make-up (content)
Electrons flow thru conduction band with out an issue
Band gap distance can be jumped; but requires some form of energy
Elergy across a band gap can.....
Absorb or emit radiation (color)
LOOK AT QUANTUM NUMBERS
DO IT BITCH
gives the shell
- ex) Na = 3, Cl=3, He =1
- values of zero to one
- s (l=0)
- p (l=1)
- d (l=2)
- f (l=3)
When selecting an instrument consider.....
D. Detection Limit
E. Dynamic Range
Method of noise reduction; assumes signal varies slowly with time; average of a small number of points
Degree of mutual agreement of data obtained
Measure of systematic error
Instruments ability to discriminate between small difference in analyte concentration.
Minimum concentration of analyte that can be detected
*signal to noise ratio = 3:1*
Signal to Noise Ratio
3 to 1
Range of concentrations at which quantitative measurements can be obtained; distance between LOQ and LOL
Limit of quantitative measurement
Limit of linear response
Degree to which method is free from interference by other species contained in the sample
Background picked up by an instrument
*always present; can be reduced.
Types of Noise:
Caused by uncontrollable variables that affect the chemistry of the system being analyzed; ex. Fluctuations in temperature, pressure, humidity, light, lab fumes, etc.
Types of Instrumental Noise:
A. Flicker Noise
B. Shot Noise
C. Thermal (Johnson) Noise
D. Environmental Noise
Thermal (Johnson) Noise
Caused by thermal agitation of electrons
Found whenever an electron crosses a junction
Sources not totally understood; inversely proportional to frequency (1/f)
Observed in different forms that originate from your surroundings; ex. Elevator, ratio, can be anything
A. Instrumental design
B. Grounding & shielding
D. Analog filtering
F. Synchronous demodulation
G. Lock-in amplifier
H. Software methods (ensemble averaging, boxcar averaging, Fourier transformation)
Scattering of light where wavelength is changed
- Scattering of molecules that are larger than the wavelength
- ex. Why the clouds are white
- Scattering of molecules that are smaller than the wavelength of radiation
- ex. Why the sky is blue
Change in the direction of a vector; small portion of incident light hits destructive interfaces and light is transmitted at all angles from original path.
Occurs when light cross an interface between media that differ in refraction index.
Ex. Puddle in middle of road; mirage
Study of interaction of electromagnetic radiation (light) and matter.
Process where a dissolved sample is vaporized
The splitting of a molecules into smaller molecules or atoms
Process by which an atom or molecules obtains a positive/negative charge due to the loss/gain of electrons
Quant Number ml
Indicates the energy shift; position in sub shell where electron resides.
S (1 spot)
P (3 spots)
D (5 spots)
F (7 spots)
Negative to positive