Instrumentation and Analytical Principles

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Instrumentation and Analytical Principles
2013-06-06 21:02:51
Polarography Spectrophotometry HPLC

Polarography, Spectrophotometry, HPLC
Show Answers:

  1. What does Polarography employ?
    Employs an electrochemical cell
  2. What type of instrumentation gradually increases the voltage applied between two electrodes of the cell in contact with a solution containing the analyte?
  3. How is the current measured in Polarography?
    Voltage change versus current plotted to produce a polargram
  4. What is true about the amount in the current and the concentration of the analyte in Polargraphy?
    Amount of increase in current (i.e. the wave height) proportional to the concentration of analyte
  5. What type of voltammetry is based on polargraphy?
    Anodic Stripping Voltammetry
  6. How does Anodic stripping voltammetry work?
    • Negative potential applied to one of the electrodes
    • Trace metal ions in the solution reduced and plated onto anodic electrode - preconcentrating step
    • Plating electrode used as anode in polargraphic cell - metal stripped off anode
    • Current flow during stripping provides polarogram that identifies and quantifies the analyte being measured (trace metals)
  7. What is used to assay heavy metals such as lead in blood?
  8. What is an instrument that uses the principle of charged particles moving through a magnetic or electric field, with ions being separated from other charged particles according to their mass-to-charge ratios?
    Mass spectrometer
  9. How is a sample separated by their mass-to-charge ratios in Mass Spectrometry?
    Electrons bombard a sample, ionizing the compound into fragment ions, which are separated by their mass-to-charge ratios
  10. How is the identification and quantification of a sample produced by Mass Spectrometry?
    • The mass spectrum produced is unique for a compound (identification)
    • The number of ions produced relates proportionally to concentration (quantification)
  11. What is a high-quality technique for identifying drugs or drug metabolites, amino acid composition of proteins, and steroids?
    Mass spectrometry
  12. What also has applications in the field of proteomics?
    Mass spectrometry
  13. How does the Mass Spectrometry work?
    • Eluate gas from a gas chromatograph may be introduced into a mass spectrometer that functions as the detector system OR
    • Liquid eluate may be introduced from a high-performance liquid chromatograph
  14. Name the components of a Mass Spectrometer
    • Ion source
    • Vacuum system
    • Analyzer
    • Detector
    • Computer
  15. What happens at the Ion Source in Mass Spectrometry?
    • Samples enter the ion source and are bombarded by the ionization beam
    • When the sample is in gas form and introduced from a gas chromatograph, the ion source may be electron or chemical ionization
  16. What component of the Mass Spectrometry bombards the sample by the ionization beam?
    Ion source
  17. What component in Mass Spectrometry prevents collision of ions with other molecules when electronic or magnetic separation is occurring?
    Vacuum system
  18. What are the types of Analyzer in Mass Spectrometry?
    • Beam type
    • Trapping type
  19. Which type of analyzer is a destructive process, where ions pass through the analyzer one time and then strike the detector?
  20. What is a beam-type analyzer, where mass-to-charge ratios are scanned during a prescribed time period to form a mass spectrum?
  21. What component of a Mass Spectrometry usually detects ions using electron multipliers, such as discrete dynode and continuous dynode electron multipliers?
  22. What component of the Mass Spectrometry converts the detector's signal to a digital form?
    Computer and software
  23. To further improve selectivity and sensitivity, what system can be used?
    Tandem mass spectrometers
  24. What type of spectrometer is used where a gas chromatograph or high-performance liquid chromatograph is connected to two mass spectrometers (GC/MS/MS) OR (HPLC/MS/MS)?
    Tandem Mass Spectrometers
  25. In Tandem Mass Spectrometers what happens?
    Ions of a specific mass-to-charge ratio are allowed to continue to the second mass spectrometer, where additional fragmentation occurs and final analysis is done
  26. Name the components of High-Performance liquid chromatograph (HPLC)
    • Solvent reservoir(s)
    • One or more pumps to propel the solvent(s)
    • Injector
    • Chromatographic column
    • Detector
    • Computer to process data and control the operation of the system
  27. What is a type of liquid chromatography where the mobile phase is a liquid that is passed over the stationary phase of the column?
    HPLC (High-performance liquid chromatography)
  28. What is the separation of the solutes in a sample governed by in HPLC?
    Governed by the selective distribution of the solutes between the mobile and stationary phases
  29. What are commonly used for the mobile phase of HPLC?
  30. Name the solvents commonly used for the mobile phase of HPLC
    • Acetonitrile
    • Methanol
    • Ethanol
    • Isopropanol
    • Water
  31. What type of elution in HPLC happens when the strength of solvent remains constant during separation?
    Isocratic elution
  32. What type of elution in HPLC happen when the strength of solvent continually increases (%/min) during separation?
    Gradient elution
  33. Name the types of elutions in the mobile phase of HPLC
    • Isocratic elution
    • Gradient elution
  34. What phase in HPLC is an organic material covalently bonded to silica that may be polar or nonpolar in composition?
    Stationary phase
  35. What are the types of phases in the Stationary phase of HPLC?
    • Normal phase
    • Reversed phase
  36. What phase of HPLC occurs when polar stationary phase and nonpolar mobile phase?
    Normal phase liquid chromatography
  37. What phase of HPCL occurs when Nonpolar stationary phase and polar mobile phase?
    Reversed phase liquid chromatography
  38. What type of delivery system in HPLC uses a solvent reservoir from which the pump can push the mobile phase through the column?
    Solvent-delivery system
  39. What component of HPLC produces a signal for ID and quantification of the solutes?
  40. What are the commonly used detectors in HPLC?
    • Spectrophotometer
    • Photodiode array
    • Fluorometer
    • Electrochemical
    • Mass Spectrometer
  41. How is the concentration of a light-absorbing analyte in solution determined?
    • A spectrophotmeter measures light transmitted by that analyte in solution
    • Such an analyte may absorb, transmit, and reflect light to varying degrees, but always of a characteristic nature for the analyte
  42. Name the components of a spectrophotometer
    • Power supply
    • Light source
    • Entrance slit
    • Monochromator
    • Exit slit
    • Cuvet/sample cell
    • Photodetector
    • Readout device
  43. What component of a spectrophotometer produces an intense, reproducible, constant beam of light?
    Light source or exciter lamp
  44. Name the types of incandescent lamps
    • Tungsten
    • Deuterium
  45. What is the Tungsten lamp used for?
    Most common, used in visible and infrared regions
  46. What is the Deuterium lamp used for?
    Used in the ultraviolet region
  47. When a lamp is changed in a spectrophotometer, what must happen and why?
    • The instrument must be recalibrated
    • Changing the light source changes the angle of the light striking the monochromator
  48. What type of monochromators are used in photometers?
    • Glass filters
    • Interference filters
  49. What type of monochromators are used in spectrophotometers?
    • Diffraction gratings
    • Prisms
  50. What is the range of wavelengths in nanometers that is transmitted by the monochromator and exit slit between two points of a spectral scan where light transmitted is one-half of the peak (maximum) transmittance?
    Bandpass or spectral bandwidth
  51. What allows lamp light to enter, and is fixed in position and size?
    Entrance slit
  52. What disperses the light into wavelengths?
  53. What selects the bandpass of the monochromator that allows light of the selected wavelength to pass throught the cuvet onto the detector?
    Exit slit
  54. What part of the spectrophotometer converts the elctromagnetic radiation (light energy) transmitted by a solution into an electrical signal that is measured?
  55. With photodetectors, what is true about the more light transmitted?
    The more light transmitted, the more energy, and the greater the electrical signal that is measured
  56. What part of the spectrophotometer is when the electrical energy from a detector is displayed on some type of digital display or readout system (which may be a chart recorder or computer printout)?
    Readout device
  57. What kind of properties does Electromagnetic radiation have?
    Wave-like and particle-like properties
  58. Describe radiant energy
    Characterized as a spectrum from short wavelength to long wavelength - cosmic, gammy rays, X-rays, ultraviolet, visible, infrared, microwaves, radiowaves
  59. Define wavelength
    The distance traveled by one complete wave cycle (distance between two successive crests) measured in nanometers (nm)
  60. If the wavelength is short, then what does that also mean?
    The shorter the wavelength, the greater the energy contained in the light, and the greater the number of photons
  61. How is light classified?
    Light is classified according to its wavelength
  62. What light classification has very short wavelengths?
    Ultraviolet (UV) light
  63. What light classification has very long wavelengths?
    Infrared (IR) light
  64. What has to happen for white light to occur?
    All visible wavelengths of light (400-700 nm) are combined
  65. What color shows when a wavelength of light transmitted (not absorbed) by an object?
    Visible color
  66. What are particles of light called?
  67. When an atom absorbs a photon, what happens to the atom?
    The atom becomes excited
  68. How do atoms become excited when an atom absorbs a photon?
    • Occurs 3 ways:
    • Electron is moved to a higher energy level
    • Mode of the covalent bond vibration is changed
    • Rotation around its covalent bonds is changed
  69. What happens when energy is absorbed as a photon, an electron is moved to a higher energy level where it is unstable?
    • An excited electron is not stable and will return to ground state
    • An electron will emit energy in the form of light (radiant energy) of a characteristic wavelength
    • Absorption or emission of energy forms a line spectrum that is characteristic of a molecule and can help identify a molecule