analysis

• Methods of Analysis in Quantitative Pharmaceutical Chemistry

  • Volumetric analysis
  • Physicochemical methods
  • Gravimetric analysis
  • Special method
• Volumetric analysis


  Determination of the volume of a solution of known concentration required to react with a given amount of the substance to be analyzed
• Physicochemical methods


  • Based on some specific physical or chemical property or properties of the substance being analyzed
  • Requires the utilization of an instrumental technique
• Instrumental techniques in physicochemical methods

  • Chromatographic
  • Spectrophotometric
  • Electrometric
  • Thermal conductimetric
  • Refractometric
  • Polarimetric
• Gravimetric analysis


  Separation by extraction, precipitation, or other means of the constituent to be determined either in the natural state or in the form of a definite compound, the composition of which is known to the analyst, and the weighing of the resulting product
• Special methods


  Those which require a distinct type of technique, such as alkaloidal assaying
• Analyte or Titrand


  Substance being analyzed
• Titrant


  Solution of known concentration
• Indicator


  Chemical which changes color at or very near the point in the titration where equivalent quantities of analyte and titrant have reacted; used to determine end points, hydrogen-ion concentration or pH, or to indicate that a desired change in pH has been effected
• Rules for the use of indicators

  • Use 3 drops of indicator test solution unless otherwise directed
  • When a strong acid is titrated with a strong alkali or vice-versa, methyl orange, methyl red, or phenolphthalein may be used
  • When a weak acid is titrated with a strong alkali, use phenolphthalein as the indicator
  • When a weak alkali is titrated with a strong acid, use methyl red as the indicator
  • A weak alkali should never be titrated with a weak acid, or vice-versa, since no indicator will give a sharp end point
  • The appearance of a color is more easily observable than is the disappearance. Therefore, always titrate where possible to the appearance of a color
• Stoichiometric point or equivalence point


  The theoretical point at which equivalent amounts of each have reacted
• End point


  The point at which there occurs a sudden change in some property of the reaction mixture, a change which is made apparent by use of indicators
• A titration is feasible only when the end point is very close to the theoretical stoichiometric point
• The surface of liquids in narrow tubes is always curved, because of capillarity; the surface or meniscus is always concave when the liquid wets the tube and convex when it does not
• Readings should always be made at the lowest point of the meniscus
• Chemical Reactions Used in Titrimetric

  • Neutralization (acid-base)
  • Oxidation-Reduction
  • Precipitation
  • Complexation
• Requirements for a reaction to be used for titrimetric analysis

  • The reaction must proceed to completion
  • The reaction must proceed in a stoichiometric manner
  • A suitable end-point-detecting device must be available
  • For direct titrimetric methods, the reaction must be rapid so a sharp end point is discernable
• % weight variation

  (actual weight per capsule / average weight of capsules) x 100
• Weight Variation Test of Tablets using Statistical Quality Control
• Preparation and standardization of 0.1 N Sulfuric acid
• Preparation and standardization of 0.1 N Sodium Hydroxide
• Assay technique of Tartaric acid