Maceration, dissolution and extraction: homogenise the sample as soon as possible to facilitate a uniform and efficient extraction of analytes from the sample matrix prior to partition, beside that a degree of matrix integrity (heterogeneity) needs to be maintained;

C oncentration: The definition and inclusion for essential element are not the same in plant and animal systems. Because the trace elements essential for plants are those elements which cannot be substituted by others in their specific biochemical roles and that have a direct influence on the organism so that it can neither grow nor complete some metabolic cycle.

P artition: transfer of an analyte or analytes from the extractant to the partitioning solvent with high efficiency;

C oncentration: do not reduce the volume of solvent by the application of too much heat, which may lead to some alteration or decomposition of the analyte. It is better to use a lower temperature, at reduced pressure if possible, to expedite rapid solvent removal. Once the solution has been reduced to a small volume, ca. 5 cm 3 , a more prudent method is to direct a stream of dry nitrogen gas onto the surface of the extract.