Vocab 2 Flashcards
Provide simultaneous detection of all the dispersed radiation at the same time in the focal plane of the detector
Multichannel Detectors
The ability of a detector to convert radiation to an electrical signal
Responsivity
Ratio of electrical output (V) to incident radiant power (W)
Responsivity
Radiant energy generates current at interface of a semiconductor and a metal
Photovoltaic cells
Incident radiation causes emission of electrons from photosensitive cathode surface
Phototubes
Several electrodes separating cathodes and anodes
Dynodes
Reverse biased p-n junction formed on SI chip causes holes in depletion layer
Si photodiode
Made of semiconductors, acts as light dependent resister
Photoconductivity Detectors
Gas heated in enclosed Golay cell cause reaction in thin membrane
Pneumatic cell
Detects changes in temp at junction between two dissimilar metals
Thermocouples
Resistance thermometer made of semiconductors
Bolometer
Insulator with special thermal and electric properties
Pyroelectric
Arrays of Si photodiodes placed in integrated circuits
Photodiode array detectors
2D array of Si photodiodes
Vidicon
Photons strike MOS on P type Si capacitor
Charge couple devices
Photons strike Si which generates positive charge
Charge injection devices
Energy decay from excited to ground state
Damped oscillating dipole function
Lifetime of decay expressed by
Classical damping constant (γ)
τ
Excited state lifetime
Fourier transformation of an exponentially decreasing amplitude function gives
Lorentzian frequency distribution
One cannot measure exactly both the momentum and position of the electron
Heisenberg uncertainty principle
The product of the uncertainty in the energy of a state and the uncertainty in the lifetime of that state is approximately = h/2π
2nd Heisenberg uncertainty principle
The apparent shift in wavelength of the signal from a source that is moving towards or away from the observer
Doppler effect
Convolution of lorentzian and Gaussian
Voigt profile
Linear combo of Gaussian and lorentzian profiles
Pseudo-voigt sum functions
Product of Gaussian and lorentzian profiles
Pseudo-voigt product functions
Strength of signal level relative to the strength of noise level
Signal to noise ratio
Lowest [analyte] in sample that can be detected but not necessarily quantified
Limit of detection
Lowest [analyte] in sample that can be determined with acceptable precision and accuracy
Limit of quantitation
Magnitude and frequency of experimental noise
Noise power spectrum
Caused when a finite number of energy carrying particles in an optical device or electrons in electrical circuit; small enough to cause detectable statistical fluctuations
Shot noise
Four main types of analog S/N enhancement
Grounding, difference and instrumentation amplifiers, analog filtering, modulation
Shielding electrical cables reduces environmental noise
Grounding
Compares reference versus sample terminal. Difference between reference and sample signal is amplified
Difference and instrumentation amplifiers
Removes high v components, reduces effects of drift and low V noise components
Analog filters
Alters some property of carrier wave by a signal so wave encodes signal info
Modulation
Electronic amplifier detects particular AC frequency signal
Lock in amplifier
Series of discrete, equally spaced windows
Boxcars
What can spectral derivatives do?
Enhance resolution; reduce background; discriminate against broad bands; reduce scattering; suppress matrix effects
Fraction of radiant power transmitted through cell
Transmittance (T)
Optical absorbency is linearly dependent on the solution concentration of the absorbing species
Beers law
Radiation scattered outside the normal range of the wavelength selector, and which is passed through monochromater
Stray light
The re-emission of radiation at longer wavelengths than the wavelength of initial absorption
Fluorescence
Determination of relationship between analyte concentration and analytical response
Calibration
Use of chemical reference materials that provide known comparison between concentration and response for calibration purposes
Standardization
Reproducibility of results, numerical agreement between replicate measurements
Precision
Measure of how close results of analytical measurements come to true value
Accuracy
Environment in which your analytical sample exists
Matrix
Substance that is added in a known constant amount to all samples, blanks, and calibration standards in an analyte
Internal standard
Absolute systematic error, relative systematic error
Bias
Blank plus three times standard deviation of blank
Detection limit
Ability to discriminate between small differences in concentration
Sensitivity
Factors limiting sensitivity
Slope and precision
Quantitative definition of sensitivity; slope of calibration curve at concentration range of interest
Calibration sensitivity
Concentration that gives a signal significantly different from the background. Lowest concentration where you can reliably distinguish signal from blank
Limit of detection (LOD)
Concentration of analyte at which calibration curve departs from linearity by a specified amount
Limit of Linearity (LOL)
Useful range of analytical method, extending from LOQ to LOL
Dynamic range
