For [Cr(H2O)6]Cl3: - Primary valence of Cr is 3+ - Secondary valence is satisfied by 6 ligands (H2O) - So secondary valence is 6 For [Co(NH3)5Cl]Cl2: - Primary valence of Co is 2+ - Secondary valence is satisfied by 5 ligands (NH3) and 1 ligand (Cl) - So secondary valence is 6

1. Modern Analytical Techniques (Chem576)
By
Dr. Mesfin Bibiso(PhD, Associate Professor)

2. Introduction
Modern Analytical techniques include:
• Structural analysis of small organic molecules
• UV, IR and MS…
• Sample preparation and micro extraction techniques in the analysis of drugs
• Solid Phase Extraction (SPE) Solid Phase Micro Extraction (SPME)
Liquid Phase Micro Extraction (LPME) Molecularly Imprinted Polimers
(MIPs)
• Chromatographic techniques GC, HPLC, GC/MS, LC/MS
• Statistics, Chemometrics

3. Introduction
• Instrumental analytical chemistry is a scientific field which includes a huge
amount of different techniques
• These techniques are widely used in different parts of the research
• Drug development, quality control, clinical diagnostics, structural analysis
and many more

4. Sample Preparation Technique
• Possible steps in sample preparation techniques include:
• Homogenization, Size reduction
• Extraction
• Concentration
• Clean-up
• Analysis

5. Sample Preparation Technique
The analytical approach
• Analyte : A substance to be measured in a given sample
• Matrix : Everything else in the sample
• Interferences: Other compounds in the sample matrix that interfere with
the measurement of the analyte

6. Sample Preparation Technique
• Analyze/Analysis: Applied to the sample under study
• Determine/Determination: Applied to the measurement of the analyte in the
sample
• Multiple Samples: Identically prepared from another source
• Replicate Samples: Splits of sample from the same source

7. Sampling
• The most important step is the collection of the sample of the material to be
analyzed
• Sample should be representative of the material
• Sample should be properly taken to provide reliable characterization of the
material
• Sufficient amount must be taken for all analysis
• Reflects the true value and distribution of analyte in the original material

8. Sample Preparation Methods
Acid Dissolution and Digestion
• Used for dissolving metals, alloys, ores, glass, ceramics
• Used for dissolving trace elements in organic materials (food, plastics)
• Concentrated acid is added to sample and then heated
• Choice of acid depends on sample to be dissolved and analyte
• Acids commonly used: HCl, HNO3, H2SO4
• HF and HClO4 require special care and supervision

9. Sample Preparation Methods
Fusion (Molten Salt Fusion)
• Heating a finely powdered solid sample with a finely •powdered salt at
high temperatures until mixture melts
• Useful for the determination of silica-containing minerals, glass, ceramics,
bones, carbides
• Salts (Fluxes) Usually Used •Sodium carbonate, sodium tetraborate(borax),
•sodium peroxide, lithium metaborate

10. Sample Preparation Methods
Dry Ashing and Combustion
• Burning an organic material in air or oxygen
• Organic components form CO2and H2O vapor leaving inorganic
components behind as solid oxides
• Cannot be used for the determination of mercury, arsenic, and cadmium

11. Sample Preparation Methods
Wet Ashing
Utilizes acid to decompose the sample.
Example: HF for dissolving silica
HF-HNO3 to dissolve nickel based alloys
HF-HNO3-HClO4 providing strong oxidizing power many matrices
HNO3-H2O2 is suitable for many biological materials

12. Sample Preparation Methods
Extraction
•Used for determining organic analytes using solvents
•Solvents are chosen based on polarity of analyte
•Common Solvents:
Hexane, xylene, methylenechloride

13. Sample Preparation Methods
Solvent Extraction
• Based on preferential solubility of analyte in one of two immiscible phases
• For two immiscible solvents 1 and 2 ,the ratio of concentration of analyte in
the two phases is approximately constant (KD)

14. Sample Preparation Methods
Other Extraction Approaches
Microwave Assisted Extraction …
Heating with microwave energy during extraction
Supercritical Fluid Extraction (SFE)
Use of supercritical CO2 to dissolve organic compounds
Low cost, less toxic, ease of disposal
Solid Phase Extraction (SPE)
Solid Phase Micro extraction(SPME)
The sample is a solid organic material extracted by passing sample through a
bed of sorbent (extractant)

15. Complexes and their Properties
• When a complex ion is formed, each ligand donates an electron pair to the metal
ion. The ligand acts as a Lewis base, while the metal ion acts as a Lewis acid
• In terms of valence bond theory, the filled orbital of the ligand overlaps with an
empty orbital of the metal ion. with an empty orbital of the metal ion
• The VB model proposes that the geometry of the complex ion depends on the
hybridization of the metal ion.

16. Complexes and their Properties
• Complexes are colored or absorb ultraviolet radiation on the
basis for spectrophotometric determination
Example: Transition metal complexes

17. Complexes and their Properties

20. Properties of complex compound

21. Properties of complex compound

22. Properties of complex compound

23. Properties of complex compound

24. Properties of complex compound

25. Properties of complex compound

26. Properties of complex compound

27. Properties of complex compound

28. Properties of complex compound

29. Typical chemical properties of complexes
 Complex ion formation
 Different Shape
 Charge The charge of the complex depends on the relative charges of the
central ion or atom and the ligands
 Different color

30. Elements of the Chemistry of Complexes
• Coordination compounds play an important role in the chemical industry
and in life itself.
• For example, theZiegler-Natta catalyst which is used for polymerization of
ethylene, is acomplex containing the metals aluminum and titanium
• Metal complexes play important role in biological systems
• For example,chlorophyll,which is vital for photosynthes is in plants, is
amagnesium complex and heamoglobin, which carries oxygen to animal
cells, is an iron complex

31. Elements of the Chemistry of Complexes
The important postulates of Werner’s theory are:
Metals exhibit two types of valence: (a) Primary valence (ionizable)
(b) Secondary valence (non-ionizable)
• Primary or ionizable valence is satisfied by negative ions and corresponds
to oxidation state of the metal
• The secondary or non ionizable valence, which is satisfied by negative,
positive or neutral groups, is equal to the coordination number of metal
ion

32. Elements of the Chemistry of Complexes
• Every metal tends to satisfy both its primary and secondary
valence.
• The secondary valence is directed toward fixed positions in
space i.e. this has spatial arrangement corresponding to
different coordination number
• For the complexes CoCl3.6NH3, CoCl3.5NH3 and CoCl3.4NH3, the
number of ionizable ions in these complexes are three, two
and one, respectively. It has been proved by precipitation
reactions and conductivity measurements

33. Elements of the Chemistry of Complexes
• On the basis of Werner’s postulate these compounds are
formulated as:
• [Co(NH3)6]Cl3 , [Co(NH3)5Cl]Cl2 and [Co(NH3)
4Cl2]Cl, respectively,
• The species inside the square brackets being the complex ion
and outside the square brackets the ionisable ions

34. Elements of the Chemistry of Complexes
Exercise
• What is the number of the secondary valence
in the following: [Cr(H2O)6] Cl3 and [Co(NH3)
5Cl]Cl2