Analytical techniques

  1. what is the principle behind spectrometry
    Measuring electromagnetic radiation using photons of energy as photons move from its excited state to ground state. Certain wavelengths of energy are absorbed and emitted. The emitted energy can be seen as colors of light
  2. what is the equation to convert transmittance to absorbance
    abs= -log(T)
  3. what is beer's law
    abs = Σbc
  4. what are and describe the components of spectrometer
    • light source - provides the electromagnetic radiation
    • monochromator - selects wavelength at a specific region
    • sample 
    • detector - converts transmitted energy to electrical energy
  5. what are the components of a monochromator
    • filter
    • prism
    • diffraction grating
  6. What is the bandpass on a monochromator
    1/5 x30 nm = 6nm
  7. at what wavelength does a tungsten light source emit
    300nm - 1200nm
  8. what wavelength does a deuterium light source emit?
  9. what wavelength does a Xe and Hg light source emit
    UV and visible spectrum
  10. what are the components of an atomic absorbance spectrometer
    • light
    • monochromator
    • heat
    • PM tube (detector)
  11. what is the purpose of a chopper and which detectors is it used for?
    • to block heat and keep light when using an atomic absorbance spectrophotometer
    • used with any detector
  12. what are the components of a fluorometer?
    • light source
    • attenuator - controls light intensity
    • primary and secondary filter
    • sample
    • detector
  13. what is the principle behind fluorometer
    measures the intensity of emitted fluorescent light as photons of energy moves from excited state to ground state.
  14. what is a bandpass?
    range of wavelengths transmitted and calculated as width at half the maximum transmittance
  15. describe the photocell
    response time
    external supply
    • cheapest
    • low sensitivity
    • no low, no high
    • slow
    • no external supply
  16. describe the phototube
    response time
    • expensive
    • middle sensitivity
    • middle linearity
    • fast response time
    • yes external supply
  17. describe the photomultiplier tube
    response time
    • most expensive
    • highest sensitivity
    • best linearity
    • fast
  18. describe the diode
    response time
    • cheap
    • high sensitivity
    • medium linearity
    • fast response time
    • responds to 1λ
  19. describe the photodiode array
    response time
    has a linear array that allows it to responds to a specific wavelength resulting in complete UV/visible spectrum analysis
  20. what are the quality assurance requirements for a spectrophotometer
    • wavelength accuracy
    • stray light
    • linearity
  21. how is wavelength accuracy checked
    checked by standard absorbing solutions/filters with absorbance of known wavelength
  22. which filters are commonly used for wavelength accuracy
    • didymium 
    • holmium oxide
  23. how is stray light QC'd
    • stray light is any outside wavelengths transmitted by the monochromator
    • most common causes are reflection of light from scratches or dust particles in light path
    • results to absorbance error especially in high absorbance range. Places limits on upper range of linearity
  24. how is linearity QC'd
    linearity is occurs when a change in concentration results in a straight line calibration curve, via Beer's law
  25. what are the advantages and disadvantages of fluorometry
    • advantages: greater specificity and sensitivity
    • disadvantage: very sensitive to environmental changes
  26. describe the principle behind fluroescence emission and excitation spectrum and its difference
    • in emission spectrum, the excitation wavelength is held constant and the emission intensity is measured as a function of the emission wavelength
    • in an excitation spectrum the emission is measured at one wavelength while the excitation wavelengths are scanned
  27. What are the components of electrophoresis
    • power supply
    • electrodes
    • buffer
    • gel 
    • images analysis
  28. what is the function of a buffer in electrophoresis
    • protein with negative charges
    • provides electric current
  29. what are the components of a chromatography
    • mobile phase (gas or liquid)
    • stationary phase (solid or liquid)
  30. what is the mode of separation for chromatography sample
    • adsorption
    • partition
    • steric exclusion
    • ion exchange chromatography
Card Set
Analytical techniques
-electromagnetic radiation -spectrophotometer -detectors -atomic abs spectrometer -fluorometer