Analysis & Structure of
Molecules
문명희
화학과 분석화학전공
CHEMISTRY
물질의
특성 및 변화
물질의 합성
유기화학
무기화학
분석
분석법개발
분석화학
에너지변화
물리화학
Analytical Chemistry & Life
Drunken driver
Athletes
River contamination
Explosives by terrorists
Food
Environments
QC in Manufacturing
Clinical Examinations
Etc.
Detection of Chemicals
Accuracy
Precision
Development of Analytical Technologies
Classical
Technologies
manual
Time taking
Labor oriented
poor detection limit
•Titration
acid-base, redox, complex
•Precipitation-Weighing
Group Analysis
•Colorimetry
litmus paper,
Computer
Robotics
Instrumental
Analysis
instrumental
reproducible
Ultra low detection
(10억분의 1영역)
•Spectrophotometric methods
X-ray, Atomic Spectroscopy
UV-VIS, IR, microwave
•Separation
(chromatography)
GC, HPLC, SFC
•Electrochemical
Classical Analytical Chemistry
•
Quantitative Analysis
–
gravimetric analysis (중량분석)
Ni
Ni-dimethylglyoxime salt (침전)
무게측정
지시약첨가
–
Volumetric analysis (부피분석)
titration (적정)
색변화관찰
What is Titration ?
Final Goal : Amount ?
농도를 아는 용액
(산, 또는 염기)
H-Acid + M-Base  BH
+ MA
types
분석대상용액
(염기 또는 산)
Acid-Base titration
Redox titration
Precipitation
Spectrophotometric
Physical Methods in AC
• A Great Advance
19th century - Atomic Spectroscopy
Chemical
compound
Ex) Na ---- 589.0 nm
Light
(bright yellow)
What if light source is plasma ?
ICP (Inductively Coupled Plasma)
Colored
light
Inductively Coupled Plasma “torch”
atomic emission
4000 ~
8000 K
plasma
load coil
(~27MHz,
2kW)
Ar 의 이온화 – coil 의 spark
Ar
sample solution
(11~17L/min)
Ce emission
ICP/ optical emission
spectrum of 100 ppm
Cerium solution
plasma continuum
140Ce+
ICPMS spectrum
of 10 ppm Cerium
Analysis of Complicated Mixtures ?
Needs Simplification of Matrix
Separation (or isolation)
Emergence of Chromatography
Chromatography
In Greek Word,
Color + To Write
1903 Tswett (Russian Botanist)
First Observed
Separation of Plant Pigments
as bands on chalk column (CaCO3)
with ether
Chromatographic Separation
M.P
Samples
Sample
A&B
Solid materials
Glass wools
A
Sample
B
Modern Instruments of Chromatography
injector
detector
pump
column
Injector
Sample
loop
column
PC
Data record
Separation Process in Chromatography
Sample Components are
carried by a mobile phase
through a bed of stationary phase
Mobile Phase :
Gas
Liquid
Stationary Phase : Solid (silica, alumina, etc.)
Liquid
Classifications by Phase Type
Mobile
Liquid
Stationary
Solid
Liquid
Gas
Solid
Liquid
Supercritical Fluid
LSC
LLC
GSC
GLC
SFC
Retention of sample molecules !
Where ? -- Stationary Phase (S.P.)
By how ? -- Various Mechansims
1. Adsorption
2. Partition
3. Ion-Exchange
4. Size Exclusion
5. Affinity
1. Adsorption
Stationary Phase - Solid : silica, alumina
LSC, GSC
Separation is due to a series of
Adsorption/Desorption Steps
Solid
(particle)
M.P.
Adsorption
Common S.P. : Silica & alumina
Both Solutes and Solvent are
attracted to the Polar Sites on the S.P.
For Separation,
Solutes need to have different degrees of
ATTRACTION to the phase
2. Partition (distribution)
Solute Partitioning between TWO PHASES
S.P.: Lig. M.P.: Gas --- GLC
S.P.: Lig. M.P.: Liq --- LLC
How does liq. S.P. exist ?
Liq. Immobilized to solid (C18-silica)
Separation is Based on RELATIVE SOLUBILITY
Phase A
Phase B
Partition
Basic Principle - similar to EXTRACTION
High Affinity (Solubility) for S.P.
Retain Longer
One phase - polar
The other phase - nonpolar
Separation of Solutes is based on
differences in this relative solubility
Example
i.e. S.P. : Nonpolar (C18)
M.P.: Water or Methanol
* separation order
- order of interaction
between C18-sample
3. Ion Exchange
Stationary Phase has ionically charged surface
interaction between
Surface-ions: counterions
S.P. : Exchange Resins (Cation, Anion Types)
sample
M.P.
+
+
+
Solid
(particle)
Ion Chromatography (IC)
Chromatographic Process to separate
Ions and some polar molecules
Stationary Phase attract ionic species
by the following principles.
Typical Mechansims
1. Ion Exchange - IEC
2. Ion Exclusion
3. Complexation Effect
Ion Exchange Chromatography
Stationary Phases
Anion Exchange Resins Cation Exchange Resin
+
resin
+
(analyte)
Ion exchange
+
R
resin
resin
NH+ ClR
H
NH+ ClH
+
+
resin
strong
resin
SO3-H+
weak
resin
COO-H+
Ion Exchange
What Affects the Separation Order ?
Ionic Charge : Larger the stronger attraction
Li+, Na+, K+ < Ca+2, Mg+2
F-, Cl-, Br-, H2PO4-, < SO42Atomic Number : Higher the larger Electron Cloud
-- stronger van der Waals Force
Li+ < Na+ < K+ , Ca+2 < Mg+2
F- < Cl- < Br- < H2PO4-
Example
Ion Exchange
Separation of Common Anions
Eluent: 1.8mM Na2CO3, 1.7mM NaHCO3
Example
Ion Exchange
Separation of Common Cations
Eluent: 20mM HCl or Methansulfonic acid
Example
Ion Exchange
Separation of Organic Acids
Eluent: 1.6mM Heptafluorobutyric acid
4. Size Exclusion
Stationary Phase : Porous Gel
Solute passes pores or is excluded
Gel Permeation Chromatography
or Gel Filtration Chromatography
polymer
M.P.
Porous
particle
Schematics of Porous Particles
being used in SEC
Size Exclusion
Large Species Elute First
since they can pass through as many pores
so they spend little time in S.P.
Various Columns needed to separate
SAMPLES of SPECIFIC SIZE RANGES
Useful for Determining
Size & Size Distribution for
Polymers, Proteins, ...
Example Application by SEC
Gas Chromatography (GC)
First Commercial Instrumental
Chromatographic System
Separation in GC
Sample should be converted to Vapor State
Mobile Phase : Inert Gas (H2, He, N2, Ar)
Types of Stationary Phases
GC
Solid (GSC) : silica gel, alumina, charcoal, etc
Liquid(GLC): nonvolatile liq. Coated on
firebrick (Chromosorb..), diatomaceous earth
thickness : ~ 0.25 mm
i.e.: Poly(dimethyl siloxane)
(Dipheny)0.05(dimethyl)0.95polysiloxane
Separation is achieved by order of Sample’s Polarity.
Nonpolar Solute - attracted to Nonpolar S.P.
Types of Columns
GC
Types of Columns
GC
Conventional
1/8-1/4 inch OD, SS or glass tube
6-20 feet in length
Capillary
0.1 - 0.5 mm ID
10-100 meters in length
OTC
WCOT
GC Operation
Isothermal : Constant Temperature
Temperature Programming :
Temp. varies during the analysis
By Increasing T,
Increase the activity
(diffusion, ad/desorption,etc.)
Increase speed
recovery
For Temperature Programming,
Solubility Variations, Volatility of Solutes should be considered
Example Applications
Example Applications
Example Applications
Chemical Structure ? By How
• Electromagnetic
- Radiation
• Electron Beam
Molecule
• Neutron
Most Typical Probe !
Electromagnetic Radiation
Measure
Physical & Chemical
changes
What is electromagnetic Radiation ?
Light, microwaves, x-rays, and TV and
radio transmissions are all kinds of
electromagnetic radiation.
They are all the same kind of wavy
disturbance that repeats itself over a
distance called the wavelength.
The different names refer to different
wavelengths.
frequency
c
E  h  h

Planck const.
Light speed
wavelength
What can happen when light shines on a material ?
heat
Visible light
Atomic
level
Inner shell
Electron transition
X-ray Diffraction
Outer shell
Electron transition
UV-VIS Spectroscopy
Atomic Absorption
Atomic Emission
Rotational Motion
NMR, MRI, ESR
Molecular vibration
IR Spectroscopy
Raman Spectroscopy
Molecular
level
X-ray Diffraction or
X-ray Crystallography
X-rays are diffracted by crystals
scattered by the electron cloud of an atom of comparable size.
Diffraction Pattern
Crystal
lattice
Molecular structure
X-Ray Diffraction (X-Ray Crystallography)
• The most straightforward way of examining the structure of a compound
Bragg’s Law
Bright X-ray:
Synchrotron radiation
High-resolution X-ray
crystallography
Conditions for constructive interference of the beam at angle θ
AP + PC = n
AP = PC = d sin θ
n = 2d sin θ
n
sin θ = 2d
1. Crystals are rotated through all angles
to obtain diffraction pattern
2. The conversion of diffraction pattern
to structure
If we know,  and θ,
We can get d (inter-atomic distance)
X-ray Diffraction or X-ray Crystallography
Light Spectroscopy II
UV-VIS Absorption Spectroscopy
• Interaction of UV-VIS light with electronic energy levels in molecules
• Good means of identification for transition metal coordination compound
or some organic compounds (double bond 포함 시료의 경우)
• Good for quantitation (정량분석, HPLC의 검출기)
• Spectral band: provides a great deal of information about the electronic structures
of molecules
S2
excited
electronic
state
S1
rotational levels
ho- h1
ho
virtual
state
overtones
v=3
Energy
Ground
state
h1
UV-Vis
absorption
Raman
Scattering
Fluorescence
IR
Absorption
v=2
v=1
NIR
Absorption
Light Spectroscopy III
IR Spectroscopy
• Information on chemical groups in molecules
• Stretching and shaking of molecules: IR region (4000 cm-1 – 200 cm-1)
• Provides ‘fingerprint’ of the various chemical groups in the molecule
(예: carbonyl group: 1700 – 1800 cm-1)
• FT-IR (fast, better resolution and S/N) see box 2
CO stretching band
Vibrational Modes of Molecules
c
E  h  h

Light speed
wavelength
Vibrations in polyatomic molecules:
linear molecule:
3N-5
(N = number of atoms)
nonlinear molecule: 3N-6
for water:
3N-6 = 3
symmetric stretch
3652 cm-1
asymmetric stretch
3756 cm-1
bend
1595 cm-1
2000
cm-1
1500
929
1000
1000
671
1500
Galactic Library
1994 [Chloroform w/ 0.75% Ethanol; liquid]
2500
1045
1522
2000
1216
2500
1425
OSU FTIR
(between NaCl plates)
2401
3000
772
1216
3021
3000
3022
absorbance
CHCl3
CHCl3 normal modes
364
Cl
667 cm-1
(sym. stretch)
Cl
4
C
cm-1
3019 cm-1
(C-H stretch)
3
9
1,2
7,8
H
Cl
5,6
760 cm-1
260 cm-1
1215 cm-1
(C-H bend)
mode labels are from Hyperchem, e vibrations are doubly degenerate
Fourier Transform IR (FT-IR)
Interferogram:
x=0
FT
x=0
Mirror travel
Single beam
spectrum of air:
100%
H2O
4000
CO2
H2O
400
Frequency, (cm-1)
Perkin Elmer Galaxy 2000 FTIR
top of
beamsplitter
He-Ne
laser
Nuclear Magnetic Resonance (NMR)
시료주입
magnet
Nuclear Magnetic Resonance
• Depends on magnetic properties of certain nuclei (H, C, F, ..)
• Certain nuclei rotates about an axis and thus have a property of spin
• A spinning charged nucleus creates a magnetic field, thus magnetic
moment.
Energy ~ radio wave 영역
Spin - spin coupling
Nuclear Magnetic Resonance I
초기 NMR:
radiowave파 : 고정된 frequency 사용
- magnetic field: 시간에 따라 변화시킴 Signal vs magnetic field
최근 NMR (Pulse FT NMR)
- 강한 radiofrequency (다양한 frequency 함유)의 pulse를 가함
- Free induction decay(FID) decayed
- Time domain의 신호를 Fourier Transformation으로 frequency의 영역으로 변화시킴
Radio frequency 영역의 빛
흡수 (megahertz)
: depends on magnetic field
and nucleus being studied
(chemical structure에 의존)
Magnetic Resonance Imaging (MRI)
Imaging tool for clear and detailed pictures of internal organs and tissues
using magnet and radio frequency
MRI is particularly good for some types of brain
tumour, for primary bone tumours and soft tissue
sarcomas and for tumours affecting the spinal cord.