2. Nature of AnaChem

• Analytical chemistry


  A measurement science consisting of a set of powerful ideas and methods that are useful in all fields of science and medicine
• Analytical chemistry techniques are in demand in industries like quality assurance, forensic science, food safety, medical technology and so much more
• The Mars rovers Spirit and Opportunity arrived on Mars for a 3 month mission


  January 2004

  
• A major result from Spirit's alpha particle X-ray spectrometer (APXS) and Mossbauer spectrometer was finding concentrated deposits of silica and, at a different site, high concentrations of carbonate
• The Pathfinder spacecraft delivered the Sojourner rover to the Martian surface

  July 4, 1997
• Analytical instruments returned information on the chemical composition of rocks and soil

  
• Investigations by the Pathfinder lander and rover suggested that Mars was at one time in its past warm and wet with liquid water on the surface and water vapor in the atmosphere

  
• The Mars Science Laboratory aboard the rover Curiosity arrived on August 6, 2012 with a host of analytical instruments on board


  Late 2011

  
• CHEMCAM (LIBS)


  The LIBS (Laser induced breakdown spectroscopy) instrument will provide determination of many elements with no sample preparation. It can determine the identity and amounts of major, minor, and trace elements and can detect hydrated minerals
• Analytical chemistry techniques


  • Soil test kit to determine nitrate, phosphate, and potassium levels
  • Water test kit to determine pH, hardness, or nitrate concentration

  
• Qualitative Analysis


  Reveals chemical identity of elements and compounds in a sample
• Quantitative Analysis


  Determines the relative amounts of each substance in a sample
• Analytes


  Components of a sample that are to be determined
• Matrix


  The material in which the analyte is found
• Assay


  Used when a material "matrix" that is known by a particular name is subjected to an analysis to determine the level of a named "analyte" substance inside the material

  
• Roles of Analytical Chemistry

  • Determine the concentrations of O2 and CO2 in blood samples
  • Measure quantities of hydrocarbons, NOx, and CO in automobile exhaust gases for emission-control devices
  • Quantitative measurements of ionized Ca in blood serum to diagnose parathyroid disease
  • Quantitative determination of N in foods to determine protein content and nutritional value
  • Analysis of steel during production for carbon, nickel, and chromium to achieve desired properties
  • Measure mercaptan content of household gas supplies to warn of dangerous leaks
  • Help farmers tailor fertilization and irrigation schedules to meet plant needs
• Chemistry is often called the central science; analytical chemistry's central position signifies its importance and breadth of interactions with many other disciplines
• Types of Analysis


  • Qualitative analysis - determine identity of analyte(s)
  • Quantitative analysis - determine quantities of known analyte(s)
• Quantitative Analytical Methods


  • Gravimetric methods - determine mass of analyte or related compound
  • Volumetric methods - use volume of reagent solution to react with analyte
  • Electroanalytical methods - measure electrical properties to determine composition
  • Spectroscopic methods - based on interaction of electromagnetic radiation with analyte
• Quantitative Analysis Flow


  1. Acquire sample

  2. Select method

  3. Process sample

  4. Carry out chemical dissolution

  5. Measure property X

  6. Eliminate interferences

  7. Calculate results

  8. Estimate reliability of results
• Choosing a Quantitative Analysis Method

  • Level of accuracy required
  • Economic factors like number of samples and components
  • Time investment for preliminary operations
• Acquiring the Sample


  • Sample must represent the bulk material composition
  • Sampling is the process of collecting a representative small mass
• Processing the Sample


  • Solid samples are ground, mixed, and stored
  • Liquid samples with dissolved gases must be contained to prevent changes
• Samples are stored for various lengths of time before analysis begins
• If the analyte is a gas dissolved in a liquid


  The sample container must be kept inside a second sealed container
• Quantitative Analysis flow chart

  1. Acquire sample

  2. Select method

  3. Is sample soluble?

  4. Carry out chemical dissolution

  5. Eliminate interferences

  6. Measure property X

  7. Calculate results

  8. Estimate reliability of results
• Replicate samples


  Masses or volumes have been determined by careful measurements with an analytical balance or with a precise volumetric device
• Replication


  Improves the quality of the results and provides a measure of their reliability
• Preparing solutions


  Ideally, the solvent should dissolve the entire sample, including the analyte, rapidly and completely
• Interference


  A species that causes an error in an analysis by enhancing or attenuating (making smaller) the quantity being measured
• No hard and fast rules can be given for eliminating interference
• Calibration


  The process of determining the proportionality constant k in the equation cA=kX
• Calculating results


  Computations are based on the raw experimental data collected in the measurement step, the characteristics of the measurement instruments, and the stoichiometry of the analytical reaction
• Evaluating results


  Providing some measure of the uncertainties associated with computed results
• Feedback Control Systems


  1. Measure actual state

  2. Determine desired state

  3. Does desired state = actual?

  4. Change control quantity
• Examples of feedback control systems include the concentration of Cl in a swimming pool or to ensure the balance of Nitrogen, Phosphorus and Potassium minerals in soil
• Feedback system


  The process of continuous measurement and control
• Feedback loop


  The cycle of measurement, comparison, and control
• A dead white-tailed deer was found near a pond in the Land between the Lakes National Recreational area in Kentucky
• Grass surrounding nearby power line poles was wilted and discolored, suggesting a herbicide containing arsenic may have been used