Transcript prezentace1

OPTICAL ANALYTIC
METHODS
SOURAL Ivo & VALENTOVÁ Marie
Characterization of
electromagnetic radiation
Energy E = [J]
Wavelength λ = [m]
Frequency f = [Hz]; ν = [Hz]
Wave number ν = [m-1]
Light speed (in vacuum)
c = 2,9979.108 m/s
Planck´s constant h = 6,625.10-34 J.s
E = h ·f
c= f · λ
Types of optic methods
1) Without energy change:
refractometry, polarimetry, nephelometry,
turbidimetry,
2) With energy change:
AAS, UV-VIS and IR spectrometry, NMR,
AES,
Refractometry
Snell´s law
light refraction
sin 
n
sin 
Refractometry
principal - detection of limiting angle
applications - verifying purity of liquid materials
Polarimetry
 ground on ability of a chemical substances to rotate
the plane of polarized light
 optically active substances
 chiral center
 chiral carbon
Polarimetry
 to the left
(levorotatory)
 to the right
(dextrorotatory)
 optical enantiomers
 polaroscopes
Polarimetry
 dextrorotatory and levorotatory mixture - racemic
mixture
α  α lc
 aeasured quantity
…… optical rotation
l…...... thickness of OAS layer (dm)
c……. mass concentration (g/cm3)
20
D
α
20
D
……
.
specific optical rotation
 applications - sugar and food industry (optical
activity of sacharides), farmacy and biochemistry
(detecting of steroids, vitamins, alkaloids)
Absorption Emission
Spectrometry (AES)
 ground on observating emission of
electromagnetic radiation of free atoms in gas state
 measured quantities -  (quality), intensity I
(mval/l) (quantity)
 intensity N N
 Boltzman´s law
e
E
Ne
N0
Ge  kTe

e
G0
E e  h  hc / 
0
AES
Flame: acetylene – air
Monochromator: selection of 
 Detector: measure/detects intensity
 Nebulizer: reduce sample to a fine spray
 Applications – detection of K+, Na+, Ca2+
(more elements when H2:O2 is used)
Atomic absorption
spectrometry
 Atomic absorption spectrometry is ground on
observation of electromagnetic radiation of free
atoms in gas state
 Measured quantities -  (quality), absorbance A
(quantity)
 Absorbance follows Bouger-Lambert-Beer´s law
A  ελ  l  c
 Application: detection of metallic elements
AAS
 Source of radiance: lamp with empty cathode composed from
measured element
 Flame: acetylene – air
 Monochromator: selection of 
 Detector: measure/detect intensity
 Nebulizer: reduce sample to a fine spray