analytical 1

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analytical 1
2012-02-13 12:17:31
analytical chemistry

analytical test 1
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  1. Define Selectivity.
    Selectivity is the ability to distinguish diferent components of a sample.
  2. Define Sensitivity.
    Sensitivity is the ability of an instrument to descriminate between small difference in [analyte].
  3. What is Analytical Sensitivity?
    Slope/Standard deviation, defined from concentration.
  4. What are the 2 factors of sensitivity?
    • 1) precision
    • 2) Slope of Calibration Curve
  5. Define Linearity.
    Linearity is in reference to the plots of a calibration curve to be one dimensional in respect to eachother with a high r^2 value close to 1.
  6. Define Range.
    Range is the area of variation in the upper and lower limits of the detection limit.
  7. What are the two kinds of ranges concerning the sensitivity of an instrument.
    When discussing the sensitvity of an instrument the two things to be considered are:

    Limit of Detection:

    Limit of quantification:
  8. Define Detection Limit i.e. Limit of dection.
    The limit of dection is the minimum amount of analyte that can be detected by a method @ a known confidence level.
  9. Define the limit of quantification.
    The limit of quantification is the smallest amount that the researcher can measure with reasonable accuracy with that instrument.
  10. What is the minimal extingguishable signal of an instrument?
    The minimal extinguishable signal of an instrament is determined by

    This is also known as calculating the figures of Marrit (FOM)
  11. What is the Nernst Equation?
  12. Define polarization.
    Polarization is the deviation of electric potential from the predicted value of the nernst equation.

    • Attributed to 2 things:
    • 1. concentration polarization
    • 2. kinetic polarization
  13. What is Kinetic Energy?
    The over potential required to overcome the activation energy
  14. grams of a solid reacted on working electrode?
    moles reacted =
  15. What is the basic set up for a 3-electrode system?
    • Working electrode: where rxn of interest occurs
    • Auxillary electrode: Completes circuit w/o adding additional
    • elecrons
    • Reference electrode: measures potential directly at the working electrode
  16. Discribe strengths and weaknesses of the voltammerty technique:

    • Strengths:
    • fast

    • Weaknesses:
    • charging current
    • can only distinguish peaks of 0.02 V apart
    • sensitivity of 10^-4
  17. Discribe strengths and weaknesses of the voltammerty technique:

    Differential pulse polargraphy
    • Strengths:
    • Peaks are more easily distinguished
    • enables the ability to distinguish peaks from 0.04 V from eachother
    • Sensivity of 10^-7 to 10^-9

  18. Discribe strengths and weaknesses of the voltammerty technique:

    square wave voltammetry

    • 1)most effective excitation signal
    • 2) Very fast 10ms to yield data
    • 3) Same sensitivity as DPP (10^-7 to 10^-9)
    • 4) high [ ] of analyte at surface
  19. Discribe strengths and weaknesses of the voltammerty technique:

    Cyclic Voltammetry

    • 1) Mostly qualitative, can be quantitative
    • 2) studies redox reactions and intermediate


    1) not as sensitivity as pulse methods
  20. Discribe strengths and weaknesses of the voltammerty technique:

    Stripping analysis

    • 1) great for small amounts of sample
    • 2) Sensitivity of ^-6 to 10^-9
  21. define frequency
    the number of oscillations of the electric field vector per unit time

    units: 1/p
  22. define velocity and units
    The velocity of a wave is the length the wave travels over time.

    This value is known as the speed of light, 3.0x10^8 m/s or 3.0x10^10 cm/s
  23. Define wavelength
    The linear distance between successive maxima or minima of a waves

    Units: cm s^-1
  24. define wave number
    Wave number is defined as the number of waves per centimeter and is equal to

    Units: cm^-1
  25. what is plank's constant and the equation to calculate energy in joules
    Plank's Constant 6.63x10^-34

  26. define Emission spectroscopy
    Emission spectroscopy is the excitation by heat or a chemical rxn (chemiluminescence) to monitor wavelengths of light that is emitted.
  27. Define: Photoluminescence spectroscopy
    excitation by electromagnetic radiation, 2 types

    • 1) fluorescence
    • 2) phosphorescence
  28. define fluorescence
    emission occurring fro s1 to s0, 10^-4 sec to 10^-8
  29. define phosphorescence
    emission occurring from T1 to S0 between states of different mutiplicity
  30. define absorbance
    pass light through a sample and measure absorbance as a funcition of wavelength
  31. What are Beers law's limitations?
    Beers Law's limitations are:

    • 1) only work ok dilute samples
    • 2) If particles are close, they will affect eatchothers charge distrucbution.
    • 3) if close, it will aslo affect the spectrum and linearity
    • 4)can get complexs and ppt that affect spectrum (chemical deviations)
    • 5) association and dissociation rxns with solvents or other molecules in matrix
    • 6) Instrument deviation, quality of monochrometer