Nanotechnology: From Microelectronics to Health Care

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Food Analysis Lecture 18 (4/1/2005)
Basic Principles of Chromatography (1)
Qingrong Huang Department of Food Science Read
Material Chapter 27, page 437 Final Exam April
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2
Dynamic Light scattering

• Originating from concentration fluctuation

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Scattered Light from Molecules in Solution

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Autocorrelation Function


The property A(t) fluctuates in time as the
molecules move around in the fluid. The time axis
is divided into Discrete intervals, ?t.
Theorem Ensemble average is equivalent to time
average.
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Instrumentation


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DLS Applications

• Determination of critical micelle concentration
  (CMC)
• Vesicle size distribution determination
• Insulin structure as a function of pH
• Thermal dissociation and denaturation of
  proteins
• Characterization of low molecular weight
  peptides
• Sizes of polysaccharide fractionations
• Stability of colloids for medical imaging
• BSA monomer and dimer
• Gold colloids, etc.

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Summary of Operation


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Data Analysis

• From correlator, intensity-intensity
  autocorrelation function, G(q,t),
• was obtained
• The normalized autocorrelation function, g(q,t),
  was calculated using
• Sigert relation
• g(q,t)G(q,t)-11/2
• William-Watts (WW)-stretched exponential
  function is used to fit
• the experimental data
• g(q,t)exp-(t/?)?
• Here ? is the distribution parameter. For
  diffusing particles of equal
• size a simple relaxation process with ?1 is
  expected. For all the
• solutions we study in the paper, ? is within the
  range of 0.9 1.
• The mean relaxation times are calculated by using

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Data Analysis (continue)

• The diffusion coefficient D were calculated
  according to Dlt?gt-1q -2,
• where q is the amplitude of scattering vector
  defined as
• q(4?n/?)sin(?/2), n is the solution refractive
  index,
• ? the laser wavelength and ? the scattering
  angle.
• The diffusion coefficient D can be converted
  into hydrodynamics
• radius Rh using the Stokes-Einstein equation
• RhkT/(6??D)

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SI Unit
Basic Units of Système International (SI) Mass
kilogramme (kg) Length meter (m) Time second
(s) temperature kelvin (K) Electrical
quantities ampère (A) Quantity of mass mole
(mol)

Derived SI units Quantity SI
unit Symbol Definition Energy Joul J kgm2s-
2 Force Newton N kgms-2 J/m Power Watt W
J/s Pressure Pascal Pa Nm-2
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Data Analysis (continue)
Constant Symbol SI Avogadros
constant N 6.02x10-23 mol-1 Boltzmanns
constant k 1.38x10-23 JK-1 Molar gas
constant RN0k 8.314 JK-1mol-1 Speed of light
in vacuum c 2.998x108 m s-1

1 poise(p) 10 g cm-1s-1 0.1 kg m-1s-1
----- -----------unit of viscosity 1cp 0.01 p

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Data Analysis (Example)


Fitting function G(q,t)ab(exp(-(t/c)d)2 Where
c (also ?) is the average relaxation time q2
(4?nsin(?/2)/?)2(43.1421.401sin(110/2)/(6.910
-5))24.371010 cm-2 D?-1 q-2 (0.000034.371010
)-1 7.6310-7 cm2/s7.6310-11
m2/s RhKT/(6??D)1.3810-23298/(63.1420.000456
7.6310-11)6.310-9 m6.3 nm
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Extraction

• Extraction the transfer of a solute from one
  liquid phase to another.
• Batch extraction the solute is extracted from
  one solvent by shaking
• it with a second immiscible solvent.
• Continuous extraction requires special
  apparatus like Soxhlet extractor.
• Countercurrent extraction a serial extraction
  process which separates
• two or more solutes with different partition
  coefficients from each other
• by a series of partitions between two immiscible
  liquid phases.

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Soxhlet Extraction

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Chromatography

• Chromatography a general term applied to a wide
  variety of separation
• techniques based on the partitioning or
  distribution of a sample (solute)
• Between a moving or mobile phase and a fixed or
  stationary phase.
• The relative interaction of a solute with these
  two phases is described by
• the partition (K) or distribution (D) coefficient
  (ratio of concentration of solute
• In stationary phase to concentration of solute in
  mobile phase.
• The mobile phase may be either gas (GC), liquid
  (LC), and supercritical
• Fluid.

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Chromatography

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Physicochemical Principles of Separation

• Adsorption (solid-liquid) chromatography
  oldest, Tsvet in 1903
• The stationary phase is a finely divided solid
  (to maximize the
• surface area),
• The mobile phase can be either gas or liquid
• The stationary phase (adsorbent) is chosen to
  permit differential
• Interaction with the components of the sample to
  be resolved.
• The interaction forces include
• - Van der Waals forces
• - Electrostatic forces
• - Hydrogen bonds
• - Hydrophobic interactions
• Typical stationary phases silica (slightly
  acidic), alumina (slightly
• Basic), charcoal (nonpolar).

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Size-Exclusion Chromatography (SEC)

• SEC, also known as Gel Permeation Chromatography
  (GPC), can
• be used for the resolution of macromolecules,
  such as proteins and
• Carbohydrates, as well as for the fractionation
  and characterization
• Of synthetic polymers.

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Chromatography