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. videovideo - Design of Experiments video VideoVideo - How to calculate relative error Video

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: х 1, х 2, х 3, х 4,…х n-1, x n. 1 x n x 1n x n x.exper. Q; 1 x n x 1 x 2 x. Q       

 If Q exper.  Q critical, then the result of determination it costs to leave for subsequent consideration  If Q exper.  Q theoret., then the result of determination needs to throw off.

The theoretical values Q-test at the different probabilities n Q 0,90 Q 0,95 30,940,94 40,760,77 50,640,64 60,560,56n Q 0,90 Q 0,95 70,510,51 80,470,48 90,440,44 100,410,42

2. Calculation the middle arithmetic to the result of measurements: 3. Calculation of the middle square deviation:

4. Calculate the dispersion of selection S 2 5. Calculation of the confidence interval

The comparison selections of results of an analysis The criterion of Fisher: 1. Calculation the dispersion of different series of measurements and 2. Calculation the experimental criterion of Fisher (must be S 1 2  S 2 2 ) exper. S S F 

If F exper.  F theoret, than the difference between dispersions is insignificant, it is possible to estimate difference between and. If F exper.  F theoret, than the difference between dispersions is insignificant, it is possible to estimate difference between and.

Criterion of Student 1. Calculation of the weighed dispersion of two selections: 2. Calculation of the experimental value the coefficient of Student:  If t  table.  t  exper., then consider that and it is possible to unite two series of results and conduct one statistical processing.. nn nn S хх t exper.     

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. The chemical method has: 1.Metrological descriptions  regularity;  producibility;  the boundary of exposure;  lower and upper boundaris of determination ;  selectivity;  sensitivity; 2. Technical descriptions:  the possibility of automation;  distance control;  expressivity;  energocapacity;

The analytical signals:  one-components (atomic-absorbcion spectroscopy)  many-components (sweepable spectrophotometry) The analytical signals : 1.integral 2.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 mutual- couplings 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 the inside-laboratory control of exactness results of QChA on procedure, regulated in the methodical of QChA ; 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; 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. 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.

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