Purpose of the Course

1
Introduction

• Purpose of the Course
• Lecture
• Introduce the methodology of analytical chemistry
• Examine the theory of wet analytical chemistry
• Wet analytical chemistry is based on ionic
  equilibria
• Examine small sample statistics
• Determine the expected reliability of an analysis
  from the quality of the apparatus and procedures
  use to make measurements propagation of
  uncertainty
• Consider experimental design so as to improve the
  reliability of experimental results
• Consider how to calculate the probability that
  two samples are not the same
• Consider how to compare the precisions of two
  analytical procedures so as to determine whether
  the differences in means are due to determinate
  or indeterminate error

2
Introduction

• Purpose of the Course
• Laboratory
• Learn the procedures that are associated with
  particular kinds of analyses
• Learn the correct ways to manipulate glassware
  and other measuring apparatus so as to obtain
  the best precision possible given the reliability
  of the apparatus
• Learn how to carry out multiple simultaneous
  procedures
• Definition of analytical chemistry involves the
  separating, identifying and determining of the
  relative amounts of the analytes in a sample of
  matter
• Qualitative analysis deals with the identity of
  analytes
• Quantitative analysis involves determining the
  relative amounts of analytes in a sample of
  matter
• Often a separation step is necessary for both
  qualitative and quantitative analysis
• The role of analytical chemistry in the sciences

3
Introduction

• Classification of quantitative methods of
  analysis
• Two measurements are required in quantitative
  analysis
• Mass or volume of sample
• A quantity proportional to the amount of analyte
  in the sample
• Gravimetric methods measure the mass of analyte
  or a compound stoichiometrically related to the
  analyte
• Volumetric methods measure the volume of a
  solution containing a substance that reacts
  stoichiometrically with the analyte
• Electroanalytical methods measure potential,
  current, resistance or quantity of electricity
  which can be related to the quantity of analyte
• Spectroscopic methods measure the interaction of
  light of matter which is related to the quantity
  of analyte
• Miscellaneous methods mass spectroscopy, rate of
  radioactive decay, calorimetry, rate of
  reaction, optical activity, refractive index,

4
Introduction

• Steps in a typical quantitative analysis See
  Figure 1-1, p 3 on Skoog, West and Holler
• Selecting a method of analysis
• Level of accuracy and precision required
• High accuracy and precision is expensive in money
  and time
• Number of samples
• Large number of samples may justify extensive and
  expensive set-up
• Few samples may reduce the need for extensive
  set-up
• Complexity and number of analytes
• Sampling
• The sample subject to analysis must be
  representative of the whole sample it must
  faithfully represent the bulk of material from
  which it was taken
• Preparation of the laboratory sample
• Solid samples must be ground
• Inhomogeneous samples must be mixed
• Samples will often be stored before analysis
• Stored samples often react with components in the
  atmosphere O2, H2O
• Samples are usually dried to avoid water
  affecting the results

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6
Introduction

• Steps in a typical quantitative analysis
• Defining replicate samples
• Multiple samples analyzed in the same way improve
  precision
• Measuring the masses or volumes must be done
  precisely and accurately using high quality
  balances and volume measuring equipment
• Preparing solutions of samples
• Most analysis involve preparing solution of
  samples
• Some samples are difficult to dissolve and
  require strong acids, strong bases, ignition in
  air or O2, redox reagents, high-temperature
  fusion with fluxes,
• Eliminating interferences species other than the
  analyte that affect the result of an analysis
• Calibration and measurement
• A physical property, X, of the analyte will be
  related to the concentration or quantity of
  analyte
• cAkX (k is easily calculated for gravimetry and
  coulometry)

7
Introduction

• Steps in a typical quantitative analysis
• Calculating results
• This is a stoichiometry problem
• Estimating the reliability of results
• An analysis without a statement of its
  reliability is useless
• This is a problem of small sample statistics
• Examine the case study of the Deer Kill given in
  the text as Feature 1-1, pages 6-10.