BS ISO 23380:2013 pdf download
BS ISO 23380:2013 pdf download.Selection of methods for the determination of trace elements in coal.
b) The laboratory-prepared ash is dissolved either by fusion (see AS 1038-14.1) or by mixed acids (nitric, hydrochloric, and hydrofluoric acids). These dissolution procedures are applicable to the analysis of coal ash. Note that thorium and uranium can form insoluble fluorides and precautions shall be taken to prevent this in the presence of hydrofluoric acid. Thorium and uranium can be determined within 2 h of the preparation ofa mixed-acid solution or the coal ash or the fluoride can be removed by evaporation.
The solution obtained by dissolution procedures in which fluoride is complexed with boric acid can be used for the determination of trace elements by ICP-AES and ICP-MS.
c) The concentrations of the analytes in the solution are determined by spectrometric techniques. Traditionally, AAS has been used. This has generally been replaced by ICP•AES. which Is used to determine the majority of these elements with the exception of antimony. cadmium, lead, thallium, thorium, and uranium. These latter six elements occur in coals at concentrations too low to be determined by ICP-AES but can be accurately determined by ICP-MS.
NOTE 2 Cadmium (see ISO 15238) and lead can also be determined by GFAAS.
5.4.2 Radionuclides
Radionuclides are naturally present in coal. The radioactivity of these can 1w measured using high- resolution gamma spcctromctry; refer to Fardy. et al,U.41, This radioactivity Is due to the decay o1238U. 235U, and 232Th and their daughters, as well as 40K and 87Rb.
5.5 Chlorine
Chlorine can be determined by a number of methods, includLng ISO 587(11 and ASTM D4O8Id. These procedures require that the coal be burnt and the chlorine trapped either in Eschka mixture or in an alkaline solution. The methods lack sensitivity and, with these procedures, repeatability levels are high. The solution obtained by pyrohydrolysis (see £6) can be used for the measurement oIchlorlnc by IC or ICP-AES. The use of XRF can provide a practical and accurate method for the determination of chlorine directly on the coal.
NOTE Chlorinr isgiiwrilIyrrporIvd nutd%d trd dLlIcrIt but isI minurdvmentindixpr vd.s.i peruentage.
5.6 Fluorine
Fluorine is determined using ISO 11724141. This method Is a pyrohydrolysis/ISE or pyrohydrolysls/IC procedure. This procedure can be used for the analysis of coal ash. There is significant evidence in the scientific literature that methods based on the decomposition of coal with an oxygen bomb combustion procedure can give low results.
5.7 Mercury
Mercury is determined using ISO 15237151. In this procedure, coal is combusted in an oxygen bomb and the released mercury absorbed In a solution of dilute nitric acid. A number of accurate alternative procedures exist for the determination of mercury. It is possible to digest coal with acids, either in a pressure vessel in a microwave oven or closed vessel in a heated water bath, or by refluxing with a mixture of nitric and sulfuric acids (see ASTM D6414). There are Instrumental techniques In which the coal is combusted and the released mercury adsorbed onto a gold collector. The mercury is subsequently thermally released and concentrated (see ASTM 1)6722).
6 Use of certified reference materials
The use of appropriate CRMs is absolutely essential when checking the accuracy of methods for the determination of trace elements in coal (see ISO Guide 33). CRMs of coal are available and are required to ascertain that there are no losses of analytes during the ashing procedure of any method. CRMs of coal ash can be used for those methods that require the ashing of the coal as a part of the procedure.
It is mandatory that verification of the method selected to determine trace elements be conlirmed by using the procedures in ISO 5725 (all parts) and that this verification be documented.
It is recommended that a CRM be analysed with each batch of samples and that the result of this analysis he reported on the test report, together with the certified or recommended values.
7 Calculation of results
The concentration of element X, Cx,i d expressed in milligrams per kilogram of coal on a dry basis, where the analyte has been determined without ashing of the sample, is calculated using Formula (1).
