In many applications the calibration procedure may be simplified without (or with tolerable)loss of the analytical precision.
Provides the digestion step dose not change the total concentration of the respective nutrients elements by contamination,evaporative losses or any other process, the original sample content can be calculated from the determined concentration by simple calculation of all dilution or concentration steps involved.this assumption has to be verified at the very beginning of an analytical procedure,i.e.,by running the specified standard through the entire procedure and calculations of the concentration