Separations Based on Complexation Reactions (Masking)
One of the most widely used techniques for preventing an interference is to bind the interferent as a soluble complex, preventing it from interfering in the analyte’s deter- mination. This process is known as masking.
Technically, masking is not a separation technique because the analyte and interferent are never physically separated from each other. Masking can, however, be considered a pseudo-separation technique, and is in- cluded here for that reason. A wide variety of ions and molecules have been used as masking agents (Table 7.6), and, as a result, selectivity is usually not a problem.
As shown in Example 7.13, a masking agent’s effectiveness can be judged by considering the equilibrium constants for the analytical and masking reactions.