QCI part 1

• Wash bottle


  Used to deliver a thin, even stream of liquid to transfer solids completely from the watch glass to the beaker or to transfer precipitates adhering to the interior of the beaker to the filter paper

  
• Rubber Policeman


  Soft rubber tube fitted to the end of a glass rod, used to loosen from the walls of the containing vessel, adhering particles
• Crucible


  Used in the ignition of most drugs and precipitates, made of high grade porcelain, withstand high temperature
• Gooch Filtration Crucible

  Designed for the separation of precipitates by suction filtration, possible to collect, wash, dry and weigh a precipitate in the same crucible
• Desiccator


  Used to maintain a dry atmosphere for objects that might be affected by moisture or carbon dioxide, used to keep samples dry while they are cooling and before they are weighed, in some cases to dry a wet sample
• Burets


  Used for the accurate transfer of a variable amount of solution, primary used is in titration/volumetric analysis - used to hold the standard solution
• Volumetric Flask


  Used to make up standard solutions to a given volume, used for the dilution of solutions to a certain volume

  
• Graduated Cylinder


  Used in making approximate measures of volume
• Pipette


  Used to transfer or deliver specific volumes or a particular volume of solution, often used to deliver a certain fraction (aliquot) of a solution
• Soxhlet Apparatus


  Used for extraction with volatile solvents where small quantities are extracted
• Muffle Furnace


  Used to ignite samples at high temperatures, either to convert precipitates to a weighable form or to burn organic materials prior to inorganic analysis, temperatures up to about 1200°C can be reached
• Cleaning of Volumetric Apparatus

  1. Warm cleaning solution (sodium dichromate in sulfuric acid)

  2. Solution of trisodium phosphate

  3. Solution of synthetic detergent
• Hot solutions should be avoided when cleaning accurately calibrated apparatus as they can cause a permanent change in volume due to thermal aftereffect
• Calibration

  The set of operations that establish, under specified conditions, the relationship between values indicated by an instrument or system for measuring (especially weighing), recording, and controlling
• Parallax Error


  Occurs during reading of the meniscus, can cause the volume to appear smaller than its actual value if the meniscus is viewed from above or larger if viewed from below, common practice is to use the bottom of the meniscus as the point of reference and have the liquid surface at eye level
• Characteristics of Analytical Procedures

  • Accuracy
  • Precision
  • Specificity
  • Linearity
  • Detection unit
  • Quantitation limit
  • Range
  • Robustness
• Accuracy


  Degree of agreement of test results with the true value, or the closeness of the results obtained by the procedure to the true value
• Precision


  Degree of agreement among individual results, the closeness of results that have been obtained exactly the same way
• Repeatability


  AKA: Intra-assay precision, expresses the precision obtained under the same operating conditions over a short interval of time
• Intermediate Precision


  Expresses within-laboratory variations, usually on different days, different analyst, different equipment
• Reproductivity


  Expresses precision between laboratories when a method is transferred from one part of a company to another
• Robustness


  The ability of the procedure to provide analytical results of acceptable accuracy and precision under a variety of conditions
• Linearity


  Indicates the ability to produce results that are directly proportional to the concentration of the analyte in samples
• Range


  An expression of the lowest and highest levels of analyte that have been demonstrated to be determinable for the product
• Specificity


  The ability to measure unequivocally the desired analyte in the presence of other components such as excipients and impurities that may also be expected to be present
• Detection Limit


  The smallest quantity of an analyte that can be detected, and not necessarily determined, in a quantitative fashion
• Quantitation Limit


  The lowest concentration of an analyte in a sample that may be determined with acceptable accuracy and precision
• Sensitivity


  Indicates how responsive it is to a small change in the concentration of an analyte
• Accuracy


  Indicates the closeness of the measurement to the TRUE or ACCEPTED VALUE and is expressed by the errors
• Absolute Error


  Difference between the measured value and the true value, mean error is the average of several measurements
• Relative Error


  Found by dividing the absolute error by the true value, the absolute or mean error expressed as a percentage of the true value
• Types of Errors in Analysis

  • Intermediate Errors (Random/Accidental Error)
  • Determinate Errors (Systemic Error)
  • Gross Errors
• Intermediate Errors


  Slight variations in a series of observations made by the observer under identical conditions, result from causes difficult to detect and impossible to eliminate, sources are differences in judgement and skill of the analyst
• Determinate Errors


  Recur in a constant manner in each of a series of determination, usually detectable and may be eliminated, sources are personal errors, errors of method, and apparatus/instrumental errors
• Gross Errors


  Usually occur only occasionally, often large, may cause result to be either low or high, often the product of human errors, easily recognized as they involve a major breakdown in the analytical process
• Animal Assays


  • Digitaloid Drugs (Digitalis, Pigeons)
  • Insulin (Rabbit)
  • Glucagon (Cats)
  • Oxytocin (Chicken/Rat)
  • Cortocotropin (Adrenocorticotropic hormone, Rats)
  • Chorionic Gonadotropin (Female Rats)
  • Heparin (Sheep)
  • Protamine Sulfate (Sheep)
  • Cod liver oil (Vitamin D Activity, Rachitic Rat)
  • Parathyroid (Dog)
  • Vasopressin (Rats)