Speciation methodologies chemical extraction

An operational definition is considerably more practical. Operationally determined species are defined by the methods used to separate them from other forms of the same element that may be present. The physical or chemical procedure that isolates the particular set of metal species is used to define the set. Metals extracted from soil with an acetate buffer is an operational definition of a certain class. Lead present in airborne particles of less than 10 pm is another. In water analyses, simply filtering the sample before acidification can speciate the analytes into dissolved and insoluble fractions. These procedures are sometimes referred to as fractionation, which is probably a more properly descriptive term than speciation, as speciation might imply that a particular chemical species or compound is being determined. When such operational speciation is done, careful documentation of the protocol is required, since small changes in procedure can lead to substantial changes in the results. Standardized methods are recommended, as results cannot be compared from one laboratory to another unless a standard protocol is followed [124], Improvements in methodology must be documented and compared with the currently used standard methods to produce useful, readily interpretable information. 

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