Assistant of the pharmaceutical chemistry department Burmas
Nataliya Ivanivna e-mail: [email protected] Physical
methods of analysis: classification and metrological
characteristics
Slide 2
Plan 1. Classification the methods of analysis, advantages and
lacks of the physical methods of analysis (PMA). 2. Metrological
characteristics of PMA and physical and chemical methods of
analysis (PCMA). 3. Refractometry. 4. Polarimetry.
Slide 3
Methods of analysis are divided into: 1.Chemical methods: -
gravimetry - titrimetry 2. Physical and chemical methods: -
electrochemical - photometric - kinetic - chromatographic 3.
Physical methods: - spectral - kernel-physical - mas-spectroscopic
- thermal 4. biological methods 1. Classification the methods of
analysis, advantages and lacks of the physical methods of analysis
(PMA)
Slide 4
Physical and physical- chemical methods of analysis are based
on the using of the relationship between measurable physical
properties of substances and qualitative and quantitative
composition. are based on the using of the relationship between
measurable physical properties of substances and qualitative and
quantitative composition.
Slide 5
Physical methods of analysis based on measuring the effect
caused by the interaction of substance with a radiation the stream
of quantum or particles. physical methods of analysis are such
methods in which identification of the element based on the
properties of its atoms and and nucleus.
Slide 6
Physical properties of materials measured by different
instruments (tools), so physical and physical- chemical methods are
called instrumental.
Slide 7
Advantage of PMA 1. High sensitivity - low limit of detection
(10 -9 mkg) and the definition. 2. The high selectivity. 3. The
expressity. 4. The possibility of automation and computerization.
5. The possibility of analysis on the distance. 6. The possibility
of analysis without destroying the sample. 7. The possibility of
local analysis.
Slide 8
Lacks of P 1. Error of determination near 5% (in special case
to 20%), then 0,01-0,005 % for gravimetry and 0,1-0,05 % for
titrimetry. 2. Reproducibility of results in the individual methods
is lower than in classical methods of analysis.
Slide 9
Lacks of P 3.The complexity of the equipment used, its high
cost and also high value of standard substances. 4.The need for
standards and standard solutions, calibration equipment and
construction of calibration graphs.
Slide 10
2. Metrological characteristics of PMA and physical and
chemical methods of analysis (PCMA) The sensitivity of method is
determined by factors: a) intensity of measured physical properties
b) sensitiveness of detectors The little-intensity properties :
refraction of light, rotation of the plane polarization of light
refractometry and polarimetry has a low sensitivity. The
hight-intensity properties : absorption of light (from nature),
fluorescence, radio-activity, emission are the sensitivity of such
methods from 10 -6 to 10 - 15 g.
Slide 11
Sensitivity of some instrumental methods of analysis
MethodLimit of exposure Photometry (PMA) 1 10 -6 Fluorimetry (PMA
and PCMA) 1 10 -10 Polarography (PCMA) 1 10 -8 Emission spectral
analysis (PMA) 1 10 -10 Atomno-absorbcition analysis (PCMA) 1 10
-10 Gas chromatography (PCMA) 1 10 -11 Radioisotope analysis (PMA)
1 10 -15 Mas-spectroscopic (PMA) 1 10 -12 Coulometry (PCMA) 1 10
-10 Kinetic analysis (PMA and PCMA) 1 10 -11
Slide 12
The selectivity of method is the selectivity determination of
this substance in presence other without of previous separation
High selectivity is inherent the methods, which are based on
characteristic properties of molecules, functional groups, atoms,
which in same queue own emission and absorbcition properties,
radio-activity, ability to electrochemical oxidization or
reduction. Low selectivity is characteristic, for example,
refractometry is used for the analysis of individual substances or
mixtures with 2-3 substances.
Slide 13
The regularity of method is closeness the got result to the
truth value of content of the determined substance in the
experimental object Depends on how measured physical property is
adequately reflects the structure and connected with it is strictly
defined by laws. Exactness of calibration of analytical equipment
will influence on the regularity of method. Depends on how measured
physical property is adequately reflects the structure and
connected with it is strictly defined by laws. Exactness of
calibration of analytical equipment will influence on the
regularity of method. The standard specimen is a substance which
has constant composition and properties. The standard specimen is a
substance which has constant composition and properties.
Slide 14
The reproducility of method characterized by variation of
results at the parallel measurings. On the producibility
influences: the exactness of measuring; the exactness of weighing;
the exactness to use of dishes; stability work of the analytical
appliance (apply the special methods of measurings).
Slide 15
3. Refractometry is a set of methods of the research of
physical and chemical properties substance are on the basis of
measuring their indexes of refraction by light. Refractometry is a
set of methods of the research of physical and chemical properties
substance are on the basis of measuring their indexes of refraction
by light. is a method of qualitative and quantitative analysis,
which is based on the measuring the index of refraction by the
liquid or crystals. Refractometry is a method of qualitative and
quantitative analysis, which is based on the measuring the index of
refraction by the liquid or crystals.
Slide 16
Index of refraction n=sin 1 /sin 2
Slide 17
widening in the present medium Absolute index of refraction (N)
is the relation of speed widening of light in the vacuum to its
speed in the present medium : Relative index of refraction (n) is
the relation of speed widening of light in the air to its speed in
the present medium:
Slide 18
Connection between the absolute and relative indexes of
refraction is described by a formula: Connection between the
absolute and relative indexes of refraction is described by a
formula:
Slide 19
The index of refraction is the difficult function which depends
from the influence of many factors: a) the nature of refractive
medium; b) light is refracted ( D =589,3 nm); c) temperature (20
0,3 ); d) the concentration of solution; e) from direction falling
on the crystal of light.
Slide 20
In these conditions measuring the refractive index has a value
between 1,3-1,7. Exactness of measuring on refractions Abbe arrives
from 0,0001 to 0,0003. In practice, refractometry is used to
determine the concentration of solution is below 3%.
Slide 21
1. Scale 2. Amicis prism (scray of dispersion) 3. Prizmenity
block 4. Lighting prism 5. Layer of examinee liquid 6. Measuring
prism 7. Crossing for adjusting of light and shade in an
eyepiece
Slide 22
Qualitative analysis Every clean, optically transparent
substance (liquid, crystal) is characterized by the defined
numerical value the index of refraction, that used in the
qualitative analysis (metanol 1,3286; ethanol 1,3613; acetone
1,3591; chloroform 1,4456; water 1,3330). Every clean, optically
transparent substance (liquid, crystal) is characterized by the
defined numerical value the index of refraction, that used in the
qualitative analysis (metanol 1,3286; ethanol 1,3613; acetone
1,3591; chloroform 1,4456; water 1,3330).
Slide 23
Quantitative analysis It is based on used of dependence between
the index of refraction by trial solution and content X of
determined substance. It is based on used of dependence between the
index of refraction by trial solution and content X of determined
substance.
Slide 24
Basic methods of quantitative analysis : 1. The method of
calibration chart 2. Calculation 3. By special of tables 3. By
special of refractometric tables
Slide 25
Advantages of the method: simplicity of apparatus design, the
speed of execution. Advantages of the method: simplicity of
apparatus design, the speed of execution. Lacks of the method: a
low exactness and a low sensitivity (the area determined of
contents) Lacks of the method: a low exactness and a low
sensitivity (the area determined of contents) The absolute error
doesn't must exceed 0,0002 - 0,005 (for medical means 0,0002)
Application: for control quality of substances, solvents and
solutions.
Slide 26
4. Polarimetry the method of analysis, which is based on
measuring of angle rotation by space polarization of the
monochromatic light at passing its through the optically active
substance an individual substance or a solution. rotation substance
rotation substance has + for right-rotation substance has - for
left-rotation substance
Slide 27
The angle rotation of space polarization depends from: a) light
b) the thickness of layer c) the nature of a solvent d) the density
of optically active medium e) the concentration of optically active
substance f) a temperature
Slide 28
Specific rotation - is the angle rotation of space polarization
of monochromatic radiation at thickness of the layer 1 dm and the
content of optically active substance 1 g/ml. the individual
substances Specific rotation by the individual substances : for
solutions of optically active substances: for solutions of
optically active substances:
Slide 29
Qualitative analysis it is based on measuring of the angle
rotation of space polarization by examinee substance or its
solution and calculation of specific rotation. it is based on
measuring of the angle rotation of space polarization by examinee
substance or its solution and calculation of specific
rotation.
Advantages of method: the simplicity of apparatus design.
Advantages of method: the simplicity of apparatus design. Lacks of
method: a low exactness and a low sensitivity (area of determined
contents). Application: a) to control the purity of substances of
optically active compounds (carbohydrates, amino acids); b) for
conformation of identity and authenticity by the size of specific
rotation (ascorbic acid, camphor, levomicetin, morphine); c) for
the quantitative determination of sugars (saccharides).