3. Sources of error

The accuracy of determinations is often difficult to ensure, due to the large number of analytical steps involved, from sample collection and preparation to the assay itself. The causes of error lie at different stages, depending on the nature of the sample. These errors result either from loss of the analyte (deficit values in the results), or from its addition through contamination (excess values).

• Losses can be caused by volatilization, absorption, adsorption, transformation, precipitation or co-precipitation as a result of the treatments used during sample preparation and dissolution. However, there are situations where they are only apparent. In other words, even in cases where there has been no loss during preparation, interference during measurement is very often responsible for signal depression (emission, absorption). These are matrix...