Nature of Analytical Chemistry

• Chemical Tests– a reagent or reagents are added to the sample to determine its composition. Example: Benedict’s test for glucose Salkowski’s test for cholesterol, Phosphate test shows yellow precipitate
• Flame Tests –detect the presence of certain elements, primarily metal ions, based on each element's characteristic emission spectrum
• Sodium– intense yellow flame
• Calcium– red flame
• Gravimetric method–determine the mass of the analyte or some compound chemically related to it.
• In gravimetric analysis, the analyte (substance of interest) is converted to an insoluble substance (precipitate) that is isolated and weighed.
• Volumetric method –the volume of a solution of a known concentration, containing sufficient reagent to react completely with the analyte is measured.
• Instrumentation methods –with the use of scientific instruments
• Electroanalytical method –study an analyte by measuring potential and/or current in an electrochemical cell containing the analyte.
• Spectroscopic method –based on the measurement of the interaction between electromagnetic radiation and analyte atoms or molecules
• Other instrumentation:

  1. Flame photometry
  2. Mass spectrometry
  3. Chromatography
  4. Electrophoresis
  5. Optical activity
  6. Refractive Index
• Qualitative –determination of identity of the chemical species
• Quantitate –determination of the relative amount of the chemical specie in each amount of sample
• • Macro analysis - amount of analyte is more than 0.10 grams (100 mg)
• • Semimicro analysis - amount of analyte is between 0.010 - 0.10 grams
• • Micro analysis — amount of analyte is 10-4 to 10-2 grams
• Ultramicro analysis - amount of analyte is less than 10-4 grams
• • Major Constituent- amount of analyte is 1-100% of the population
• • Minor Constituent- amount of analyte is 0.1-1% of the population
• • Trace Constituent- amount of analyte is .01-0.1% (1ppb-100ppm) of the population
• • Ultratrace Constituent- amount of analyte is below 1ppb
• Sampling- is the process of collecting a small mass of a material whose composition accurately represents the bulk of the material being sampled. It is the most difficult aspect of analysis
• • Real samples- Analysis of real samples are complicated because of the presence of sample matrix
• Sampling process must ensure that the items chosen are representative of the bulk of material or population.
• Gross samples - these are representative samples that are collected from the source
• Laboratory samples - these are samples that are reduced in size and being homogenized so that they are measurable in the lab