1、International Standard ( 7814 0 N 4 4g!i!i INTERNATIONAL ORGANIZATION FOR STANDARDlZATlON*MEXUlYHAPOHAR OPrAHH3AUHR l-l0 CTAH for the other clauses, see IS0 78/2. The aim in elaborating this part of IS0 78 has been to provide editors with a guide which can be used wherever possible. Where this stand
2、ard layout cannot be followed exactly, it will be for editors to modify the recommended layout, adapting it to analytical demands. In particular, the description of certain determinations will not require the inclusion of all the clauses or sub-clauses provided in the layout, while in other cases ex
3、tra clauses or sub-clauses may occasionally be needed. Consequently, the only inflexible rules are the following : a) use the terminology given in IS0 6955; b) where possible and justifiable, include the clauses and sub-clauses indicated in the layout, and arrange them in the sequence indicated (it
4、is possible and even advisable to rear- range them where strictly following the plan would lead to sub-clauses having little meaning); c) only ignore instructions given in this part of IS0 78 if they are not applicable. 2 Introduction This clause can usefully make reference to IS0 6!356 and speciall
5、y to its annex about safety, and to IS0 6955 for the cor- rect nomenclature. 3 Field of application This clause shall contain exact indications on the field of application of the method (definition of products to which the method is applicable, limit of content for which the method is valid). In add
6、ition to these indications it is necessary to report the interfering constituents as well as their contents which give interferences (see sub-clause 5.2 of IS0 6955) or the inter- ferences of other origin which render inapplicable the specified procedure. This clause should also indicate any special
7、 cases and the clauses in which they will be dealt with. 4 References This clause must contain a complete list of all documents or International Standards which are indispensable for the appli- cation of the specified method of analysis. NOTE - This list shall not include technical documents which a
8、re merely used as references in the preparation of the method; such documents can be mentioned in the clause ( Bibliography D. 5 Principle This clause should indicate concisely the essential steps of the method (preferably using substantive phrases), excluding details relating to the procedure. It s
9、hall thus, on the one hand contain the physical and chemical principles of preparations (e.g. : ashing, solution preparation, extraction, separation, addition of complexing agents and spectrochemical buffers) preceding the stage corresponding to the atomic absorption spectrometry and, on the other,
10、the characteristics of this stage. With regard to this last statement, it shall mention: a) the type of atomizers (see clause 2 of IS0 6555); b) the wavelength(s) of the line(s) used; c) the type of detection and correction of non-specific at- tenuation; d) the type of method (see sub-clause 6.1 of
11、IS0 69551, namely : I) direct method of determination, 2) determination by the bracketing technique, 3) (analyte) addition technique, 4) reference-element technique, 5) indirect method. 6 Reagents This clause, set out in accordance with the details given in IS0 78/2, shall indicate in particular how
12、 the standard solution for the members of the set of calibration solutions shall be prepared. The quality of reagents should be precisely indicated and also, where necessary, the processes of checking and purification. 7 Apparatus It is not necessary to include in this list ordinary laboratory appar
13、atus required to carry out the method. 3 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 78/4-1983 (El On the other hand, it should define the particular equipment an
14、d for the spectrometer it should indicate a) the source(s) emitting the characteristic lines; b) the type and the characteristics of the atomizer (type of burner, type of gases, etc.); c) the maximum permissible spectral bandwidth for the wavelengths of the spectral line(s) and the necessity or not
15、of a device for correcting random fluctuations; d) other special devices. Where necessary, include a reference to IS0 6956 with regard to the performances which may be required and for checking the condition of the equipment. 8 Procedure It should be remembered that the layout that is the subject of
16、 this part of IS0 78 should not be regarded as universally ap- plicable. In some circumstances, preliminary tests should be foreseen designed, for example, to detect or correct non- specific attenuation (see IS0 6956). It is then for the editor to decide how the corresponding sub-clauses should be i
17、nserted between the sub-clauses provided for in the layout, how to make the text understood and how best to carry out the method. The following is the only inflexible rule : as far as possible, in- clude each time all the sub-clauses indicated in this clause and arrange them in the sequence given. 8
18、.1 Test portion The recommendations to follow for editing the sub-clause con- cerning the amount of sample for analysis by mass or by volume are those given in sub-clause 13.2 of IS0 78/2. 8.2 Treatment of test portion (or Preparation of test sample for presentation to instrument) The mass or the vo
19、lume of the test portion for analysis is given as a guide; as it is a function of the sensitivity of the apparatus and of the calibration range selected, it may be reduced or in- creased. According to this hypothesis, the editor should in- dicate the maximum and minimum permissible concentrations of
20、 the sample in the test sample for presentation to instrument. This sub-clause should indicate with precision all physical and chemical treatments which the test portion for analysis has to undergo prior to the spectrometric measurement. The editor should not hesitate to describe the minor details c
21、apable of in- fluencing the quality of the results. 8.3 Preparation of the blank test This sub-clause should indicate how to prepare the blank test solution (see definition 5.4.4 of IS0 6955) before introducing it into the atomizer. In certain cases, the indications will conveniently be made by refe
22、rence to the sub-clause dealing with the preparation of the test sample for presentation to instrument (case of a sample not containing the analyte). 8.4 Preparation of the set of calibrating solutions This sub-clause should indicate the concentration of standard solutions which shall be used to for
23、m the different members of the set of calibrating solutions, from the zero member to the member containing the maximum permissible quantity of the element to be determined. The range of the set of calibration solutions is given as a guide; being a function of the instrumental sensitivity, it can be
24、varied slightly. In the latter case, it is for the operator to adjust the concentration of analyte in the test sample for presentation to instrument in order to obtain optimum conditions, after check- ing that the possible interferences remain corrected and that others do not appear. 8.5 Calibration
25、 and determination 8.5.1 Spectrometric measurements This sub-clause should indicate a) the wavelength(s) at which measurements should be made ; b) if necessary, the observation height (see IS0 6955 clauses 2.3.13) : c) in the case of flames, the characteristics of the flame (oxidizing or reducing) ;
26、 d) in the case of a flameless atomizer, the exact indica- tions of the permissible amount of analyte for each measurement, the time and the temperature of different stages of the cycle leading to atomization, as well as the quality of materials constituting the atomization enclosure and its geometr
27、y; e) the solvent blank for zero absorbance adjustment of the instrument (see definitions 5.4.2 of IS0 6955 and 4.2.4 of IS0 6956). 8.5.2 Analytical function (or Plotting calibration graph) This sub-clause may sometimes be replaced by a phrase incor- porated in the preceding sub-clause, for example:
28、 “Plot the analytical curve from the values obtained”. In other cases, however, it may be appropriate to give detailed instructions. It is useful to indicate for at least one of the members of the range an approximate value for the absorbance which should be obtained. 4 Copyright International Organ
29、ization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8.5.3 Blank test IS0 78/4-1983 (E) 10 Precision This sub-clause should be included if the blank test solution dif- fers from the zero number of the set
30、 of calibrating solutions and is then used to correct the measurements carried out on the samples. 9 Expression of results This clause should indicate how the value of the parameter sought should be calculated starting from a) the analytical function obtained according to 8.5.2; b) the result of the
31、 measurement obtained according to 8.5.1; c) if necessary, the result of the measurement obtained according to 8.5.3; d) the quantity of test portion (8.1) used. In addition it should show clearly the units employed. The clause should bring together, in addition to precision (repeatability and repro
32、ducibility), all the factors capable of defining the suitability of the method i.e. the sensitivity, the ac- curacy and the reliability (see definitions 6.2.1, 6.2.5 and 6.2.9 in IS0 6955). 11 Special cases This clause should bring together all the alterations in the pro- cedure necessitated by the
33、presence or the absence of specific elements in the product to be analysed. It is preferable for the sake of greater clarity, even if the altera- tion is very slight, to draft a clause entitled “Special case” rather than describe the alteration in a note. However, if the alterations involve very imp
34、ortant modifica- tions, it is preferable to draft another document. 12 Bibliography If it is necessary to mention bibliographical references, follow the form provided in IS0 690. 5 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
