1. Introduction to Analytical Chemistry

2. What is Analytical Chemistry?
Analytical chemistry seeks ever improved means of measuring the chemical composition of natural and artificial materials
The techniques of this science are used to identify the substances which may be present in a material and determine the exact amounts of the identified substances
Qualitative: provides information about the identity of an atomic, molecular or biomolecular species
Quantitative: provides numerical information as to the relative amounts of species
Definitions from

3. The Role of Analytical Chemistry
-Friedrich Wilhelm Ostwald
“Analytical Chemistry, or the art of recognizing different substances and determining their constituents, takes a prominent position among the applications of science, since the questions which it enables us to answer arise wherever chemical processes are employed for scientific or chemical purposes.”

4. The Role of Analytical Chemistry
Analytical chemists work to improve the reliability of existing techniques to meet the demands of for better chemical measurements which arise constantly in our society
They adapt proven methodologies to new kinds of materials or to answer new questions about their composition.
They carry out research to discover completely new principles of measurements and are at the forefront of the utilization of major discoveries such as lasers and microchip devices for practical purposes.
Medicine
Industry
Environmental
Food and Agriculture
Forensics
Archaeology
Space science
All branches of chemistry draw on the ideas and techniques of analytical chemistry

5. History of Analytical Methods
Classical methods: early years (separation of analytes) via precipitation, extraction or distillation
Qualitative: recognized by color, boiling point, solubility, taste
Quantitative: gravimetric or titrimetric measurements
Instrumental Methods: newer, faster, more efficient
Physical properties of analytes: conductivity, electrode potential, light emission absorption, mass to charge ratio and fluorescence, many more…

6. Classification of Modern Analytical Methods
Gravimetric Methods determine the mass of the analyte or some compound chemically related to it
Volumetric Methods measure the volume of a solution containing sufficient reagent to react completely with the analyte
Electroanalytical Methods involve the measurement of such electrical properties as voltage, current, resistance, and quantity of electrical charge
Spectroscopic Methods are based on the measurement of the interaction between electromagnetic radiation and analyte atoms or molecules, or the production of such radiation by analytes
Miscellaneous Methods include the measurement of such quantities as mass-to-charge ratio, rate of radioactive decay, heat of reaction, rate of reaction, sample thermal conductivity, optical activity, and refractive index

7. Analytical Methodology
1. Understanding and defining the problem
2. History of the sample and background of the problem
3. Plan of action and execution
4. Analysis and reporting of results

8. 1. Understanding and Defining
the Problem
What accuracy is required?
Is there a time (or money) limit?
How much sample is available?
How many samples are to be analyzed?
What is the concentration range of the analyte?
What components of the system will cause an interference?
What are the physical and chemical properties of the sample matrix? (complexity)

9. 2. History of sample and background
of the problem
Background info can originate from many sources:
The client, competitor’s products
Literature searches on related systems
Sample histories:
synthetic route
how sample was collected, transported, stored
the sampling process

10. 3. Plan of Action Performance Characteristics: Figures of Merit s2
Which analytical method should I choose? How good is the measurement, information content
How reproducible is it? Precision
How close to the true value is it? Accuracy/Bias
How small of a difference can be measured? Sensitivity
What concentration/mass/amount/range? Dynamic Range
How much interference? Selectivity (univariate vs. multivariate)
bias =  - xt s2
Sm = Sbl+ ksbl
S = mc + Sbl

11. 4. Analyzing and Reporting Results
No work is complete until the “customer” is happy!
Analytical data analysis takes many forms: statistics, chemometrics, simulations, etc…
Analytical work can result in:
peer-reviewed papers, etc…
how sample was collected, transported, stored
technical reports, lab notebook records, etc...

12. Components of an Analytical Method
Obtain and store sample
Pretreat and prepare sample
Extract data
from sample
Perform measurement
(instrumentation)
Compare results
with standards
3-Processing the Sample
-Preparing Solutions: Physical and Chemical Changes
-Most analyses are performed on solutions of the sample made with a suitable solvent. Ideally, the solvent should dissolve the entire sample, including the analyte, rapidly and completely. The conditions of dissolution should be sufficiently mild that loss of the analyte cannot occur or is minimized.
-Conversion of the analyte in insoluble materials into a soluble form is often the most difficult and time-consuming task in the analytical process
-At this point in the analysis, it may be possible to proceed directly to the measurement step, but more often than not, we must
eliminate interferences in the sample before making measurements
4-Eliminating Interferences
-Eliminate substances from the sample that may interfere with the measurement step
-Species other than the analyte that affect the final measurement are called interferences
-A scheme must be devised to isolate the analytes from interferences before the final measurement is made.
-Techniques or reactions that work for only one analyte are said to be specific
-Techniques or reactions that apply for only a few analytes are selective
5-Calibration and Measurement
-All analytical results depend on a final measurement X of a physical or chemical property of the analyte, which must vary in a known and reproducible way with the concentration of the analyte
-Ideally, the measurement of the property is directly proportional to the concentration, where k is the proportionality constant
-The process of determining k is called calibration
6-Calculating Results
-Computing analyte concentrations from experimental data is usually relatively easy
-Computations are based on raw experimental data collected in the measurement step, the characteristics of the measurement instruments, and the stoichiometry of the analytical reaction
7-Evaluating Results by Estimating Their Reliability
-Analytical results are incomplete without an estimate of their reliability.
-The experimenter must provide some measure of the uncertainties associated with computed results if the data are to have any value
Apply required
statistical techniques
Covert data
into information
Verify results
After reviewing results
might be necessary
to modify and repeat
procedure
Transform
information into
knowledge
Present information
Handbook, Settle

13. Techniques Separation Techniques Gas chromatography
High performance liquid chromatography
Ion chromatography
Super critical fluid chromatography
Capillary electrophoresis
Planar chromatography
Spectroscopic techniques
Infrared spectrometry (dispersive and fourier transform)
Raman spectrometry
Nuclear magnetic resonance
X-ray spectrometry
Atomic absorption spectrometry
Inductively coupled plasma atomic emission spectrometry
Inductively coupled plasma MS
Atomic fluorescence spectrometry
Ultraviolet/visible spectrometry (CD)
Molecular Fluorescence spectrometry
Chemiluminescence spectrometry
X-Ray Fluorescence spectrometry

14. More Techniques Mass Spectrometry Electron ionization MS
Chemical ionization MS
High resolution MS
Gas chromatography MS
Fast atom bombardment MS
HPLC MS
Laser MS
Electrochemical techniques
Amperometric technique
Voltammetric techniques
Potentiometric techniques
Conductiometric techniques
Microscopic and surface techniques
Atomic force microscopy
Scanning tunneling microscopy
Auger electron spectrometry
X-Ray photon electron spectrometry
Secondary ion MS

15. Aqueous Solution Equilibria
Equilibria classified by reaction taking place
1) acid-base
2) oxidative-reductive
Bronsted-Lowry definitions: acid: anything that donates a [H+] (proton donor) base: anything that accepts a [H+] (proton acceptor)
HNO2 + H2O  NO2- + H3O+
NH3 + H2O  NH4+ + OH-
Kb = [NH4+][OH-] / [NH3]
BASE
HA + H2O  A- + H3O+
Ka = [A- ] [H3O+ ] / [HA]
ACID

16. Strength of Acids and Bases
Source:

17. p-Functions
The p- value is the negative base-10 logarithm of the molar concentration of a certain species:
pX = -log [X] = log 1/[X]
The most well known p-function is pH, the negative logarithm of [H3O+].
pH = - log [H3O+]
pKw = pH + pOH = 14
We can also express equilibrium constants for the strength of acids and bases in a log form
pKa = - log(Ka)
pKb = - log (Kb)
Kw = Ka * Kb

18. Strength of Acids and Bases
Source:

19. Titrations
Definition: an analytical technique that measures concentration of an analyte by the volumetric addition of a reagent solution (titrant)- that reacts quantitatively with the analyte
For titrations to be useful, the reaction must generally be quantitative, fast and well-behaved
Advantages Disadvantages
great flexibility large amount of analyte required
suitable for a wide range of analytes lacks speciation (similar structure)
manual, simple colorimetric -subjective
excellent precision an accuracy sensitive to skill of analyst
readily automated reagents unstable

20. Chemical Stoichiometry
Stoichiometry: The mass relationships among reacting chemical species. The stoichiometry of a reaction is the relationship among the number of moles of reactants and products as shown by a balanced equation.
Mass
Moles
Divide by molar mass
Multiply by stoichiometric
ratio
Multiply by molar mass

21. Titration Curves
Strong acid - Strong base
Strong base - Weak acid

22. Titration Curves
Strong base - polyprotic acid

23. Buffer Solutions
Buffers contain a weak acid HA and its conjugate base A-
The buffer resists changes in pH by reacting with any added H+ or OH-, preventing their accumulation. How?
Any added H+ reacts with the base A-:
H+ (aq) + A- (aq) -> HA(aq) (since A- has a strong affinity for H+)
Any added OH- reacts with the weak acid HA:
OH- (aq) + HA (aq) -> H2O + A-(aq) (since OH- can steal H+ from A-)
Example: if 1 mL of 0.1 N HCl solution to 100 mL water, the pH drops from 7 to If the 0.1 N HCl is added to a 0.01 M solution of 1:1 acetic acid/sodium acetate, the pH drops only 0.09 units.

24. Calculating the pH of Buffered Solutions
Henderson-Hasselbach equation

25. Example 1
30 mL of 0.10M NaOH neutralised 25.0mL of hydrochloric acid. Determine the concentration of the acid
1.Write the balanced chemical equation for the reaction NaOH(aq) + HCl(aq) -----> NaCl(aq) + H2O(l)
2.Extract the relevant information from the question: NaOH V = 30mL , M = 0.10M HCl V = 25.0mL, M = ?
3.Check the data for consistency NaOH V = 30 x 10-3L , M = 0.10M HCl V = 25.0 x 10-3L, M = ?
4.Calculate moles NaOH n(NaOH) = M x V = 0.10 x 30 x 10-3 = 3 x 10-3 moles
5.From the balanced chemical equation find the mole ratio NaOH:HCl 1:1

26. Example 1 (continued) 6.Find moles HCl NaOH: HCl is 1:1
So n(NaOH) = n(HCl) = 3 x 10-3 moles at the equivalence point
Calculate concentration of HCl: M = n ÷ V
n = 3 x 10-3 mol, V = 25.0 x 10-3L
M(HCl) = 3 x 10-3 ÷ 25.0 x 10-3 = 0.12M or 0.12 mol L-1

27. Example 2
50mL of 0.2mol L-1 NaOH neutralised 20mL of sulfuric acid. Determine the concentration of the acid
1.Write the balanced chemical equation for the reaction NaOH(aq) + H2SO4(aq) -----> Na2SO4(aq) + 2H2O(l)
2.Extract the relevant information from the question: NaOH V = 50mL, M = 0.2M H2SO4 V = 20mL, M = ?
3.Check the data for consistency NaOH V = 50 x 10-3L, M = 0.2M H2SO4 V = 20 x 10-3L, M = ?
4.Calculate moles NaOH n(NaOH) = M x V = 0.2 x 50 x 10-3 = 0.01 mol
5.From the balanced chemical equation find the mole ratio NaOH:H2SO4 2:1

28. Example 2 (continued) 6.Find moles H2SO4 NaOH: H2SO4 is 2:1
So n(H2SO4) = ½ x n(NaOH) = ½ x 0.01 = 5 x 10-3 moles H2SO4 at the
equivalence point
7.Calculate concentration of H2SO4: M = n ÷ V n = 5 x 10-3 mol, V = 20 x 10-3L
M(H2SO4) = 5 x 10-3 ÷ 20 x 10-3 = 0.25M or 0.25 mol L-1

29. Notes on Solutions and Their Concentrations
Molar Concentration or Molarity – Number of moles of solute in one Liter of solution or millimoles solute per milliliter of solution.
Analytical Molarity – Total number of moles of a solute, regardless of chemical state, in one liter of solution. It specifies a recipe for solution preparation. 
Equilibrium Molarity – (Species Molarity) – The molar concentration of a particular species in a solution at equilibrium.
Percent Concentration
a. percent (w/w) = weight solute X 100%
weight solution
b.volume percent (v/v) = volume solute X 100%
volume solution
c.weight/volume percent (w/v) = weight solute, g X 100% volume soln, mL

30. Some Other Important Concepts
Limit of detection (LOD): the lowest amount (concentration or mass) of an analyte that can be detected at a known confidence level
Linearity: the degree to which a response of an analytical detector to analyte concentration/mass approximates a linear function
Limit of linearity
Slope relates to sensitivity
Detector response
LOQ
LOD
Dynamic range
Concentration
Limit of quantitation (LOQ): the range over which quantitative measurements can be made (usually the linear range), often defined by detector dynamic range
Selectivity: the degree to which a detector is free from interferences (including the matrix or other analytes)

31. Concentration in Parts per Million/Billion
ppm:
cppm = mass of solute X ppm
mass of solution
For dilute aqueous solutions whose densities are approximately 1.00 g/mL, 1 ppm = 1 mg/L
ppb:
cppb = mass of solute X ppb

32. Density and Specific Gravity of Solutions
Density: The mass of a substance per unit volume. In SI units, density is expressed in units of kg/L or g/mL.
Specific Gravity: The ratio of the mass of a substance to the mass of an equal volume of water at 4 degrees Celsius. Dimensionless (not associated with units of measure).

33. Other Helpful Information
Prefixes for SI Units
giga- G 109
mega- M 106
kilo- k 103
deci- d 10-1
centi- c 10-2
milli- m 10-3
micro- u 10-6
nano- n 10-9
pico- p 10-12
femto- f 10-15
atto- a 10-18