Section 1
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Signal processors
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Last updated
6 years ago
Date created
Mar 1, 2020
Cards (107)
Section 1
(50 cards)
Signal processors
amplify convert so its easily displayed
advantages of fourier
Jaquinot- high throughput high resolving power wavelength reproduction all wavelengths hit detector at once multiplex disadvantage
Interferogram
a graph of output light intensity vs. retardation DISCRETE
Youngs experiment
Intensity of bands as a function of distance along length of screen
Coherent Radiation
-two sources=IDENTICAL frequencies -Phase relationship CONSTANT
X ray
ionizing radicals
amount of groves in a grating
300-2000
Uncertainty
width is 0 if lifetimes are infinite
Commonly used in HPLC
photodiodes
triplet excited is
lower in energy NOOOOOO spin
narrow lines reduce
possibility of interferences
infrared
vibrate/ rotate
Phototube
converts energy of an incoming photon into a current pulse on PHOTOEMISSIVE SURFACE
Photoelectric effect
Pressure Broadens lines by
2-3 Orders of magnitude
Why is a photodiode detector an amazing idea
-simultaneous measurements at many wavelengths -rapid
Decreasing slit width results in _______ resolution
greater spectral resolution
List forms of readout
-computer display -digital or analog readout -strip chart recorder -integrator
What three things are proportional (energy)
E, frequency, waveNUMBER
Heated objects emit radiation
blackbody radiation
Photoelectrons are attracted to
+ dynode, cascade of electrons
amplification of a photomultiplier tube
10 to the 6th
Dispersion
the ability to separate a wavelength
multiplex disadvantages
flicker noise causes degradation of S/N
Atomic line widths are influenced by 4 things
-Uncertainty effect -Doppler -Pressure Broadening -Electronic and magnetic field effects
Wavelength filters
interference absorption (visible)
Lithium
106 lines
Czerney Turner Monochromator
grating isolates individual wavelengths of light
Photomultiplier tube
sealed QUARTZ with an inert gas current pulse is recorded for each incident photon.
Cuvette for visible region
glass or plastic
list the electrical components of light
-transmission -reflection -refraction -absorption
Two types of detectors
heat, photon
Examples of discrete light sources
Hollow Cathode Lamp EDL (electrodeless discharge lamp)
Cuvette for UV or visible
quartz or silica
Microwave
rotate
Chapter 7
Sodium
170 lines
Iron
2340 lines
Doppler shift..... broadens lines by
2 orders of magnitude
fluorescence
light
What controls sampling interval in a interferogram
a laser beam
List the optical methods
-UV -Visible -IR
Photodiode arrays are sensitive to EMR in
visible and ultraviolet regions
Monochromator
prism grating
temp effects
-increases efficiency of the atomization process -line broadens -decrease in peak height -degree of ionization
Visible
excitation
Effective Bandwidth
inverse measure of the quality of the device
advantages of FTIR
-improved S to N ration -better frequency accuracy -speed -built in data handling capabilites
Filters
promotes or removes certain bands of radiation
Emission
heat
Section 2
(50 cards)
spectral
when absorption or emission spectra of an interfering species gets close to that of the analyte
Polarization
Deformation of electron clouds
HCL
Ne or Ar at low vaccuum Lamps receive an applied potential of 300 V DC
how to back ground correct in GFAAS
zeeman background
list types of instrumental noise
-shot -flicker -environmental -thermal
shot noise
current moving across a junction
chemical
species in sample matrix interfere with atomization (changes volatility)
In solvents, what is highly restricted?
rotational and vibrational transitions------> leads to broad band absorption
Beers law only works if
light is MONOchromatic <20 nm, dilute
EDL
-quartz tube -argon gas and metal of interest -HIGH vacuum -RF coils -10x more intense than HCL buuuut only works for 15 elements
Modulation
low frequency or dc signals from transducers are converted to a higher frequency amplified filtered with high pass filter demodulated low pass filter
lock in amplifier
coordinates signal between the chopper and the detector identifies the signal being received at the detector
refraction index for liquids
1.3-1.8
heating steps in GFAA
dry ash/ char atomize
if size of particles is large
Scattering
How does HCL work
1. 300 V DV ionizes inert gas 2. Gas generates curent flow in lamp 3. metal ions on cathode get energy and dislodge into vaccuum 4. cloud forms around cathode -----> sputtering 5. some cations excite and return to groud= emit 6. sputter redeposit on cathode/ glass surface
GFAA is very sensitive
over a flame
Refraction is caused by
2 materials w different densities
COLORS AND WAVELENGTHS pg 21 ch 6
Thermal noise other names
johnson noise root mean square voltage white noise
How to get a range in atomization temperatures
changing and varying the fuel/oxidant mixtures
Bends to normal
Less dense to more dense
how does EDL work
-microwave field applied to quartz -Ar gas ionizes -energy is transferred to metal upon collision -metals that are excited return to ground state
How is flame created in FAAS
fuel+ oxidant
Zeeman
-light is passed through polarizer -absorption of analyte occurs at one phase -absorption of blank occurs at both subtracted
Refract index for solids
1.3-2.5
Unique about GFAAs
background correction methods
If size of particles are small
little scattering
things that cause excitation
-absorption of EMR -Electrical discharge -high temp -electron bombardment
Incoherent Radiation
Light emitted by individual events to make a sum of all events
Dispersion
light hits and causes dipole variation in refractive index
flicker noise
is frequency dependent and worse at low frequencies
Signal to noise enhancements
-hardware devices -grounding and shielding - difference amplifiers -analog filtering
List some types of atomizers
Flame Electric Arc Electric spark
Types of emission
-Atomic -X ray -Fluorescence -phosphorescence
thermal noise
thermal agitation of electrons in electrical components inhomogeneities---> voltage fluctuations
if molecules absorbs light
anomalous dispersion
types of noise
-chemical noise - instrumental noise
how to back ground correct in FAAS
continuous light
atomization
analytes of a sample are decomposed and converted to atoms/ions in gaseous state
two types of AAS interference
Spectral Chemical
Raman scattering (inelastic) detector is
around sample
where does atomization occur?
in a flame in an electrically heated graphite tube flushed with inert gas
GFAAS use ____ samplers
auto
instrumental noise is associated with
each component
Absorption, detector is
after sample
Chemical interference in detail
change in the atomization behavior of analyte atomization signal depressed comes from analysis of an analyte in low concentration in a complex matrix
noise degrades
accuracy and precision
Refract index for glass
1.5
The atomization process is the
signal generator
Section 3
(7 cards)