Analytical Method I

• What are the four basic disciplines in analytical techniques?

  Spectrometry, Luminescence, Electroanalytic Methods, and Chromatography
• What are the subcategories of Spectrometry?

  • Spectrophotometry
  • Atomic Absorption (AAS)
  • Mass Spectrometry (MS)
• What are the subcategories of Luminescence?

  • Fluorescence
  • Chemiluminescence
• What are the subcategories of Electroanalytic Methods?

  • Electrophoresis
  • Potentiometry / Amperometry
• What are the subcategories of Chromatography?

  • Gas
  • Liquid
  • Thin-Layer
• What is the primary goal of photoelectric colorimetry?

  The primary goal is the isolation of discreet portions of the spectrum for purposes of measurement
• What is the difference between spectrophotometric measurement and photometric measurement?

  Spectrophotometric measurement considers the wavelength, while photometric measurement does not.
• How does spectrophotometry determine the concentration of a substance?

  It measures the light transmitted by a solution to determine the concentration of the light-absorbing substance.
• What is a single beam spectrophotometer?

  It is the simplest type of spectrophotometer designed to make one measurement at a time at one specified wavelength.
• What is the function of a double beam spectrophotometer?

  It splits monochromatic light into two components, one passing through the sample and the other through a reference solution.
• What are the two types of double beam spectrophotometers?

  Double beam in space and double beam in time.
• What are the basic components of a single or double-beam configuration spectrophotometer?

  1. Stable source of radiant energy
  2. Filter
  3. Sample Holder
  4. Radiation detector
  5. Signal Processor
  6. Readout device
• What is the visible light spectrum range?

  350 to 700 nm
• What is the role of the light or radiant source in a spectrophotometer?

  It provides polychromatic light and must generate sufficient energy to measure the analyte of interest.
• What are the two types of light sources used in spectrophotometers?

  Continuum source and line source.
• What is the function of the entrance slit in a spectrophotometer?

  It minimizes unwanted or stray light and prevents the entrance of scattered light into the monochromator system.
• What is the purpose of the monochromator in a spectrophotometer?

  It isolates specific or individual wavelengths of light.
• What are the two types of monochromators?

  Prism and diffraction gratings.
• What is the function of the exit slit in a spectrophotometer?

  It controls the width (bandpass) of the light beam, allowing only a narrow fraction of the spectrum to reach the cuvette.
• What is a cuvet in the context of a spectrophotometer?

  It is a container that holds the solution whose concentration is to be measured.
• What are the types of cuvets used in spectrophotometry?

  1. Alumina Silica Glass
  2. Quartz or Plastic
  3. Borosilicate Glass
  4. Soft Glass
• What is the significance of the path length of a cuvet?

  The path length affects the absorbance; a longer path length increases sensitivity.
• What is the function of the photodetector in a spectrophotometer?

  It detects and converts transmitted light into photoelectric energy.
• What are the types of photodetectors used in spectrophotometry?

  1. Barrier Layer Cells
  2. Phototube
  3. Photomultiplier Tube (PMT)
  4. Photodiode
• What is Beer’s Law in the context of spectrophotometry?

  It states that the concentration of the unknown substance is directly proportional to the absorbed light and inversely related to the transmitted light.
• What is percent transmittance?

  It is the fraction of incident light that is transmitted through a substance.
• What is the blanking technique in spectrophotometry?

  • A blank contains serum without the reagent to complete the assay.
  • Reagent blank corrects absorbance caused by the color of the reagent.
  • Measures absorbance of the sample and reagent in the absence of end product.
  • May require ultracentrifugation in cases of turbidity.
• What is the significance of spectrophotometer quality assurance?

  • Ensures accurate wavelength measurement.
  • Maintains reliability of results.
  • Validates the performance of the spectrophotometer.
• What is the speed of visible light?

  300,000 km/s
• What happens to light as it passes through a prism?

  It is refracted, allowing only the desired wavelength to pass through an exit slit.
• How does the function of a prism differ from that of a diffraction grating in a monochromator?

  A prism refracts light, while a diffraction grating bends wavelengths as they pass through grooves.
• What is the role of filters in a spectrophotometer?

  Filters produce monochromatic light based on the principle of constructive interference of waves.
• What is the importance of the bandpass in a spectrophotometer?

  The bandpass determines the total range of wavelengths transmitted, affecting the resolution.
• What is the maximum absorbance limitation caused by stray light?

  Stray light limits the maximum absorbance that a spectrophotometer can achieve.
• What is the effect of scratches on the optical surface of a cuvet?

  Scratches will scatter the light and should lead to the cuvet being discarded.
• What happens if an alkaline solution is left standing in a cuvet?

  It could dissolve the glass, producing etching.
• What is the typical path length of a cuvet?

  1 cm
• How does increasing the path length of a cuvet affect absorbance?

  It increases the absorbance for a given solution by a factor of 10.
• What should be the orientation of the arrow on a cuvet?

  The arrow should be placed facing towards the light source.
• What is the maximum volume that should be filled in a cuvet?

  The maximum volume is usually 1 ml.