Analysis Techniques

Prof.Dr. Figen KAYA

LECTURE

• YOU WIL SELECT A REPRESENTATIVE

• SOME LECTURE NOTES AND HANDOUTS WILL BE PROVIDED

http://www.yarbis.yildiz.edu.tr/fkaya-Duyurular

• ONE MIDTERM EXAMINATIONS

• HOMEWORK ASSIGMENTS

RULES

• ARRIVE TO CLASS ON TIME

• DO NOT READ ANYTHING ELSE (NEWSPAPER) IN CLASS

• MOBILE PHONES

• ASK QUESTIONS IN ENGLISH

Course Materials • ASM Handbook Volume 10 Materials Characterization, ISBN 0-

87170-007-7 • Materials Characterization; An Introduction to Microscopic and

Specroscopic Methods, Y.Leng, Wiley Publishing ISBN 978-0-470-82298-2

• Chemical Analysis, Modern Instrumentation Methods and Techniques, F.Rouessac, A.Rouessac, Wiley Publishing, ISBN 978-0-470-85903-2

• Principles of Instrumental Analysis, D.A.Skoog, F.J.Holler, T.A.Nieman, Saunders College Publishing. ISBN0-03-002078-6

• Quantitative Chemical Analysis, D.C.Harris. W.H.Freeman and Company ISBN:0-7167-4464-3

What is Analysis?Analysis: What are the constituents of the sample?Analytical chemistry deals with methods for determining the chemical composition of samples of matter.

Analysis could be classify into two categories:1- Qualitative Methods2- Quantitative Methods

Constituent: A component part of something (i.e. Composite, cpompound, mixture etc.) Hot water Coffee granules Sugar Milk Cream Cacao powder

Qualitative Analysis:The aim of qualitative analysis is a complete, detailed description. Qualitative method yield information about the identitiy of atomic or molecular species or the functional groups in the sample.→Which atom/atoms, molecule/molecules are coming together in the make up of the sample?

Group= Green tokens (pieces)+Yellow tokens+Blue tokens+Red tokens

Quantitative AnalysisQuantitative Analysis; we classify features, count them, and even construct more complex statistical models in an attempt to explain what is observed.Quantitative method provides numerical information as to the relative amount of one or more of these companents.→How many/ how much grams? volumes? of atom/atoms or molecule/molecules in the sample

Group= 6 Green tokens (pieces)+8 Yellow tokens+6 Blue tokens+10 Red tokens

Classification of Analytical Methods1- Classical Methods (Wet Chemical Methods):The analyses are carried out by seperating the components of interest (analytes) in a sample by;*Precipitation, *Extraction*Distillation.

For qualitative analses, the seperated components are treated with reagents that yielded products that could be recognised by;→their colors, → their boiling or melting points, → their solubilities in a series of solvents,→their odors,→ their optical activities,→their reactive indexes

• Reagent: A substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs.

Reagent: Cobalt(II)thiocyanateC2CoN2S2→ RedAfter reaction with cocaine

→ turns to Blue

• Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic (i.e. alkaline) conditions.

• hydroxyphenoxazone

For quantitative analyses, the amount of analyte is determined by gravimetric or by titrimetric measurements.• Gravimetric measurement: the mass of the

analyte is determined.• Titrimetric measurement: The volume or mass

of a standart reagent required to react completely with the analyte is measured.

Instrumental Methods:Use of physical properties of analytes such as;→Conductivity→electrode potential→light absorption or emission→flourescence to analyse quantitative analysis of samples.Seperating and determining chemical make up of a sample by machines and devices.

Instrumental Methods:

Instrumental Methods could be classify into 4 different groups:1) Spectroscopic Methods2)Electrochemical Methods3) Cromotographic Methods4) Thermal Methods

Spectroscopy• What Is Spectroscopy?

Spectroscopy is a technique that uses the interaction of energy with a sample to perform an analysis.

Studying the properties of matter through its interaction with different frequency components of the electromagnetic spectrum.Latin: “spectron”—ghost or spiritGreek: “ σκοπειν ”—to see

SpectrumWith light, you aren’t looking directly at the molecule—the matter—but its “ghost.” You observe the light’s interaction with different degrees of freedom of the molecule. Each type of spectroscopy—different light frequency—gives a different picture X Rays → XRD spectrum.UV light → UV spectrumIR (Infra Red) light → IR-Raman spectrum

Electromagnetic wave (radiation) is an energy form that may be propagated through space and may interact

with atoms and molecules to alter their energy state.

• What is a Spectrum? The data that is obtained from spectroscopy is called a spectrum. A spectrum is a plot of the intensity of energy detected versus the wavelength (or mass or momentum or frequency, etc.) of the energy.

Goals:

• Understand how light interacts with matter and how you can use this to quantitatively understand your sample.• Understand spectroscopy the way you understand other common tools of measurement like the watch or the ruler.• See that spectroscopy is a set of tools that you can put together in different ways to understand systems → solve chemical problems.

The immediate questions that we want to address are:

• What does light do to sample?• How do you produce a spectrum?• What EXACTLY is a spectrum a measurement of?

What does a spectrum measure?

Interaction of light with a sample can influence the sample and/or the light.Method involves: (1) excitation and (2) detection.

• Excitation: The activity produced in any system that is caused by stimulation.

In most spectroscopies, we characterize how a sample modifies light entering it.

1) Absorption: Change in intensity I of incident lightSample attenuates light → transmission T=I/I0

Absorption:

• We measure the absorption of light at different frequency or wavelength.

2) Emission: Excitation induces emission of light from the sample

Includes: • Fluorescence (emission from excited electronic singlet states)• Phosphorescence (emission from excited electronic triplet states)• Raman Scattering (light scattering involving vibrational transition) (usually of

different frequency).

3) Optical Rotation: Change of phase of light incident on sample (rotation of polarization)

What Are Types of Spectroscopy?

There are as many different types of spectroscopy as there are energy sources! Here are some examples:1. Atomic (Optical) Emission Spectroscopy2. Atomic Absorption Spectroscopy 3. Inductively Coupled Plasma Atomic Emission Spectroscopy4. UV- Visible Absorption Spectroscopy5. Infra-Red Spectroscopy (IR/FT-IR)6. Raman Spectroscopy7. X Ray Diffraction8. X Ray Flourescence spectrometry9. Mass spectrometry10. X-ray photoelectron spectroscopy (XPS) 11. Auger electron spectroscopy (AES),

Let’s work on describing absorption.

What are the axes?

X-axis: Characterizes the input light in terms of frequency-wavelength-energy• Wavelength λ (nm, μm, Å),• Frequency ν (cycles/sec or s-1 or Hz)

• Energy (expressed as eV or as cm-1)E = hν

λ→Wavelengthυ→frequencyc →Speed of light

Y-axis: Absorption= (Beer’s Law)I0 = light intensity incident on the sampleI = light intensity after the sampleε = molar decadic extinction coefficient (M−1cm −1 ) – absorption coefficientc = concentration (M)L = sample length (cm)

Electromagnetic wave (radiation) is an energy form that may be propagated through space and may interact with atoms and molecules to alter their

energy state.

What Information Is Obtained?A spectrum can be used to obtain information on;→atomic and molecular energy levels,→ molecular geometries, → chemical bonds, → interactions of molecules, and related processes. Often, spectra are used to identify the components of a sample (qualitative analysis). Spectra may also be used to measure the amount of material in a sample (quantitative analysis).

What Instruments Are Needed?

There are several instruments that are used to perform a spectroscopic analysis. In simplest terms, spectroscopy requires;→An energy source (commonly a laser, but this could be an ion source or radiation source) and

What Instruments Are Needed?

→ A device for measuring the change in the energy source after it has interacted with the sample (often a spectrophotometer or interferometer).

Dedector: