ANACHEM LEC MIDTERMS

• Analytical Chemistry


  • Measurement science
  • Set of powerful ideas and methods
  • Uses methods and instrumentation to investigate chemical and biological systems
  • Medicine, industry environmental quality, food, forensic analysis, etc.
  • Used to maintain quality control and assurance
• Analyst


  • They design, carry-out and interpret measurements
  • The selection and utilization of suitable chemical procedures; familiar and have the ability to operate varied range of instruments
  • Have sound knowledge of statistical treatment of experimental data
• Qualitative Analysis


  Reveals the identity (characteristics of properties) of the constituents (elements & compounds) in a sample
• Quantitative Analysis


  Indicates the amount of each substance in a sample
• Analytes


  The components of a sample (product)
• Functions of Analytical Chemistry

  • Fundamental Research - identification of its constituents by qualitative chemical analysis
  • Product Development - the design and development of a new product. Examples: developments of alloys & polymer composites
  • Product Quality Control - it ensures that the requirements are met. Uniform product quality
  • Monitoring and Control of Pollutants
  • Medical and Clinical Studies
• Definition of Terms


  • Accuracy - the closeness of an experimental measurement or result to the true or accepted value
  • Analyte - constituents (element and compound) which are studied by quantitative or qualitative approach
  • Precision - how close the measurements of the same object are close to each other
  • Assay - a highly accurate determination
  • Background - that proportion of a measurement which arises from sources other than the analyte itself
  • Blank - a measurement or observation in which the sample is replaced by a simulated matrix
  • Calibration - a procedure that enables the response of an instrument related to mass, volume, or concentration
  • Concentration - amount of a substance present in a given mass or volume of another substance
  • Constituent - a component of a sample
  • Detection Limit - the smallest amount or concentration that can be detected
  • Determination - quantitative measure with an accuracy better than 10%
  • Equivalent - amount of a substance that produces, reacts w/ or can be directly equated to one mole
  • Estimation - a semi quantitative measure of amount of an analyte, having an accuracy no better 10%
  • Interference - an effect which alters or obscures the behavior of an analyte
  • Internal Standard - the compound or element that is added to all calibration standard standard & sample– constant known amount
  • Masking - treatment of a sample w/a reagent to prevent interference
  • Matrix - the remainder of the sample– analyte forms a part
  • Method - the overall description of the instructions for a particular analysis
  • Precision - the random or indeterminate error associated w/a measurement or result– variability or reproducibility
  • Primary Standard - a substance whose purity and stability are well established
  • Procedure - a description of the practical steps involved in an analysis
  • Reagent - the chemical used to produced a specific reaction
  • Sample - the substance or portion of a substance
  • Sensitivity - the change in the response from an analyte relative to a small variation in the amount being determination
  • Standard - a pure substance that reacts in a quantitative and known stoichiometric manner
  • Standard Addition - the method of a quantitative analysis whereby the response from an analyte is measured before and after adding a known amount of an analyte to the sample
  • Standardization - determination of the concentration of an analyte or reagent solution from its reaction w/a standard
  • Technique - the principle upon which a group of methods is based
  • Validation of Methods - it is essential to validate the method by analyzing standards which have an accepted analyte content, and a matrix similar to that of the sample
• Classifying Quantitative Analytical Methods

  • Gravimetric Methods - determine the mass of the analyte
  • Volumetric Method - determines the volume of a solution
  • Electroanalytical Methods - involved in the measurement of such electrical properties like watts & voltage
  • Spectroscopic Methods - measurement of the interaction between electromagnetic radiation and analyte atoms or molecules
• Remain Steps of a Typical Quantitative Analysis

  • Calibration and Measurement - Ideally, the measurement of the property is directly proportional to the concentration
  • Calculating Results - Computing analyte concentrations 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 by Estimating their Reliability - Analytical results are incomplete without an estimate of their reliability
• Analytical Problem & Their Solution

  • Choice of Method - the selection of the method of analysis is a vital step in the solution of an analytical problem
  • Sampling
  • Preliminary Sample Treatment
  • Separations - A large proportion of analytical measurements is subject to interference from other constituents of the sample. Interference or interferent - species that causes an error in an analysis
  • Final Measurement
• Law of Conservation of Mass


  • Atoms cannot be created or destroyed in a chemical reaction
  • A balanced equation has the same number of atoms of each element on both sides of the equation
• Oxidation-Reduction


  • Oxidation - loss of electrons of an atom
  • Reduction - gain of electrons of an atom
  • Both processes occur together in a single reaction called an oxidation−reduction or redox reaction. Thus, a redox reaction always has two components, one that is oxidized and one that is reduced
  • A redox reaction involves the transfer of electrons from one element to another
  • GEROA - gain electrons=reduction, oxidizing agent
  • LEORA - lose electrons = oxidation, reducing agent