Mercury in air/water:

Metallic mercury is important as it forms amalgam with other metals. Its alloy with silver was earlier used by dentists for dental filling though it is no longer so because of toxicological effects known since several years. Mercury in air is collected through bubbling air by an acidic KMnO₄ solution where volatile elemental mercury is trapped by oxidising it to Hg²⁺. The excess permanganate is decreased along with hydroxylamine, and the collected mercury (or mercury in a water sample) is then reduced to the element by SnCl₂ according to following equations.

5Hg⁰  + 2MnO^-  ₄ + 16H⁺     → 5Hg²⁺ + 2Mn²⁺ + 8H₂O

6MnO^-₄   + 5NH₂OH + 13H⁺   → 6Mn²⁺   +  5NO^-3 + 14H₂O

Hg²⁺ + SnCl₂ + 2Cl^- →         Hg⁰ + SnCl₄

As elemental mercury has appreciable vapour pressure at room temperature, and by bubbling argon through the solution, mercury vapour is swept within a quartz ended cell whereas its atomic absorption is measured at 253.6 nm using mercury line. A calibration curve should be prepared before the sample is run. At least two blanks should also be prepared in the similar manner, omitting further of mercury. The measured absorbance is corrected for the blanks and the amount of mercury is determined from the calibration curve.

Similarly, the water sample from river, tap, or other sources could be analysed. Tap water should hold around 1 ppb or less mercury. In such determinations the water samples and the standards should be run in a similar manner. As in the case of air samples, the correction should be made for the reagent blank as its magnitude will generally govern the detection limit of the procedure. Extreme care must be taken to minimise reagent and glassware contamination. From the calibration graph the quantity and concentration of mercury in the sample is determined.