Lecture 3
The metrological providing of the
quantitative chemical analysis
ass. N.I. Burmas
Outline
1. The basic metrological descriptions of an
analysis.
2. The statistical processing results of an
analysis.
3. The methods valuation of regularity of an
analysis.
4. The metrological providing of quantitative
chemical analysis.
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1. The basic metrological descriptions
of an analysis.
The basic metrologic descriptions method of
analysis belong:
 regularity;
 producibility;
 the coefficient of sensitiveness;
 the limit of exposure;
 lower and upper limits of determination;
 selectivity.
2. The statistical processing results of
an analysis.

The selection is an aggregate statistically
equivalent of results.
The sequence of processing:
1. Verification on the presence of rough errors
by of Q-test:
х1, х2, х3, х4,…хn-1, xn
x
Q
=
.
exper.
2
- x
x
1
;Q
x
n
- x
1
exper..
=
- x
n
x
n
n- 1
- x
1
.
 If Qexper. Qcritical , then the result of
determination it costs to leave for
subsequent consideration
 If Qexper. Qtheoret., then the result of
determination needs to throw off.
The theoretical values Q-test at
the different probabilities
n
Q0,90
Q0,95
n
Q0,90
Q0,95
3
0,94
0,94
7
0,51
0,51
4
0,76
0,77
8
0,47
0,48
5
0,64
0,64
9
0,44
0,44
6
0,56
0,56
10
0,41
0,42
2. Calculation the middle arithmetic to the
result of measurements:
n
-
x=
3.
Calculation
deviation:
S=
of
x
i =0
n
the
i
;
middle
( x - x )
n-1
i
2
square
4. Calculate the dispersion of selection S2
5. Calculation of the confidence interval
S
x = x
t
n
i
 ,n
The comparison selections of results of an
analysis
The criterion of Fisher:
1. Calculation the dispersion of different
series of measurements S and S
2. Calculation the experimental criterion of
Fisher (must be S12S22 )
2
1
F
=
.
exper
.
S
2
1
S
2
2
2
2
If Fexper.  Ftheoret, than the difference
between dispersions is insignificant, it
is possible to estimate difference
between X 1 and X .
2
Criterion of Student
1. Calculation of the weighed dispersion of two
-2
selections:
(n1 - 1)S12  (n 2 - 1)S 22
S =
n1  n 2 - 2
2. Calculation of the experimental value the
coefficient of Student: х1 - х 2
n1n 2
t  exper.. =
S
2

n1  n 2
.
 If t table.t exper., then consider that X - X = 0
and it is possible to unite two series of results and
conduct one statistical processing.
1
2
3. The methods valuation of regularity of an
analysis.




the method of standard specimens;
the method of change mass of the known
quantity of the determined substance;
the method of addition of the known
quantity of the determined substance (the
systematic error is proportional to
content of the determined substance Δх =
bх)
the method of change of method analysis
4. The metrological providing of the quantitative
chemical analysis.
1.






The chemical method has:
Metrological
2. Technical descriptions:
descriptions
 the possibility of
regularity;
automation;
producibility;
 distance control;
the boundary of exposure;  expressivity;
lower and upper boundaris  energocapacity;
of determination ;
selectivity;
sensitivity;


1.
2.


The analytical signals:
one-components (atomic-absorbcion
spectroscopy)
many-components (sweepable
spectrophotometry)
The analytical signals :
integral
differential:
on the form (differential spectrophotometry) ;
on the nature (gas chromatography with two
columns, two-radiation spectrophotometer,).
The specific of chemical analysis:
1. Measured simultaneously often enough the
few quantities - contentses. That is why at first
of all there is procedure of authentication with
the
use
of
standards.
2. The measuring is carried by indirect
personality: measured not quite number of
particles , and certain parameters in the
chemical, physical and chemical and physical
methods
of
analysis.
3. An analysis is complicated by the mutualcouplings of components.
The basic stages and the source errors of
chemical analysis
1. The selection of middle (satis factory)
sample.
2. The translation is in a form, comfortable for
an analysis:
 previous enriching
 chemical processing
 often the special preparation of surface
3. The dividing of components sample is into
separate groups.
The basic stages and the source errors of
chemical analysis
4. The translation determined of component
in an analytically active form.
5. The determination is measuring of
physical property.
6. An evaluation content of determined
component is on the calibration chart or
the calibration dependence, the calculation
of a formula.
The basic stages and the source errors of
chemical analysis
7. Calculation and evaluation of
reliability results of an analysis.
8. The analysis (logical and
mathematical) of the got results and
work of recommendations for
optimization of chemical analysis.
4. The metrological providing of the quantitative
chemical analysis (QChA).
The scientific basis of the
metrological
providing
of
quantitative chemical analysis are
theoretical
and
methodical
positions of a metrology and
the analytical chemistry.
The metrological providing of QChA includes
for it self the next types of works:
1) establishment of the norms errors of results of
QChA;
2) recreation and transmission of the sizes units
of physical sizes, which characterize
composition of substances or their properties
which are functionally related with
composition of these substances ;
3) the development of standard specimens,
attested mixtures, standard reference
information and recommended standard
information.
The metrological providing of QChA includes
for it self the next types of works:
4) the providing of the same type uses is in QChA
of means measurings at development, to the
issue in an appeal, exploitation and repair and
their the accordance;
5) the standard charts or other normative
documents;
6) the providing methods of QChA of fulfilment
necessary of the metrological requirements;
7) the metrological control of QChA.
The metrological providing of QChA includes
for it self the next types of works:
8) development complex of normative
documents, positions, rules on
providing of necessary exactness of
results of QChA;
9) the state supervision and known
control after the status of QChA,
including metrological attestation of
the analytical laboratories.
The metrological control of QChA is
conducted by:
 the inside-laboratory control of exactness results of
QChA on procedure, regulated in the methodical of
 QChA ;
 the inside-laboratory statistical control of exactness of
the results of QChA on procedure, regulated in the
particular branch spheres on the control exactness of
results of QChA;
 an external control the quality of work analytical
laboratories on procedure, regulated in the particular
branch documents on a control of the exactness results
of QChA and the documents of a national standard.
Thanks you for attention!