Metal ions daily allowance

The analyst uses ICP-OES (inductively coupled plasma, optical emission spectroscopy) to measure twenty different metal ions in solution. To fully calibrate the instrument requires the preparation and measurement of 100 individual calibration standards (five point calibration per element). It would be impracticable for an analyst to calibrate the instrument daily. The instrument is calibrated at regular intervals (say fortnightly) by the analyst. In the intervening time, the calibration for each metal ion is checked by the use of a set of drift correction standard solutions. Minor corrections can then be made to the calibration to allow for day-to-day drift. 

From Fig. 1 it is evident that even essential metal ions, if they occur in a too high concentration, may lead to deleterious effects. This recognition has led to the definition of daily allowances, i.e., the dietary intake of a given element which a human may consume per day. A number of... 

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