BS ISO 16729:2013 pdf free
BS ISO 16729:2013 pdf free.Soil quality一Digestion of nitric acid soluble fractions of elements
A test portion is digested in concentrated nitric acid by means of microwave heating with a suitable laboratory microwave unit. The samples and acid(s) are placed in a fluorocarbon polymer or quartz microwave vessel or vessel liner. The vessel is sealed and heated in the microwave unit. After cooling, the vessel contents are filtered, centrifuged or allowed to settle and the clear solution is separated and diluted to volume and analysed by the appropriate measurement method.
Due to the volatility of some compounds care shall be taken that the sample is not heated before the digestion and that any volatile reaction products formed during the digestion do not escape.
The container in which the sample is delivered and stored can be a source of errors. The material shall be chosen according to the elements to be determined; e.g. elemental Hg can penetrate polyethylene walls very fast in both directions. Glass can contaminate samples containing e.g. B, Na, K, Al.
A few refractory sample matrix compounds, such as quartz, silicates, titanium dioxide, alumina and other oxides may not be dissolved. These bound elements are considered non-mobile in the environment and are excluded from most aqueous pollution transport mechanisms.
High acid and solute concentrations in the digest that cause interferences shall be properly addressed during determination.
Ensure that the complete test portion is brought into contact with the acid mixture in the digestion vessel.
There is a potential for vigorous reaction, especially with samples containing volatile or easily oxidized species. When digesting a matrix of this type, use no more than a 0,1 gsample to begin with. Ifa vigorous reaction occurs upon addition of reagent(s), allow the sample to pre-digest in the uncapped digestion vessel until the reaction ceases. Heat may be added during this step for safety considerations (for example, the rapid release of carbon dioxide from carbonates, easily oxidized organic matter). Once the initial reaction has ceased, the sample may continue through the digestion procedure.
If the digested solution is filtrated, take care that the filtration procedure does not introduce contamination.
Use only acids and reagents of recognized analytical grade to avoid high blank values for subsequent analytical measurements. Use a test blank solution throughout the procedure applying all steps with the same amount of acids, but without a sample.BS ISO 16729 pdf download.
