Calibration Curve and Standard Additions Techniques

Overview

Both the accuracy and precision of ICP measurements is dependent, in part, upon the calibration technique used. This section is focused upon errors (both fixed and random) that can be introduced through the use of different calibration techniques using accurate calibration standards, samples that have been prepared accurately to within defined error limits, and an instrument that has been 'set-up' correctly using a procedure programmed where there are no spectral/mass interferences that include background correction. You may believe that if the above errors have been confined to within acceptable and known limits that there is nothing else to worry about. Unfortunately, this is not the case.

The most common calibration technique options for ICP measurements are calibration curve and standard additions. In addition, the option of using internal standardization is available for the calibration curve technique and the ability of matrix matching may also be available. ICP-MS has the added option of using an internal standard that is an enhanced isotope of the element being measured (i.e., isotope dilution ICP-MS). This discussion will be limited to the above approaches, to the introduction of the analyte as a nebulized solution, and to the use of Ar as the plasma gas.

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