Determination of lead:
As you know, lead is another highly toxic element which is an environmental contaminant. It enters within biological systems such as plants and animals and reaches blood, urine, teeth, bones, hair, plant and animal tissues, etc. These materials need to be analytically assessed for the amount of lead so that its damage potential can be ascertained. From the viewpoint of occupational and environmental toxicology the determination of lead in blood is the most important since the concentration of lead in whole blood is considered to be the best indicator of current lead exposure in humans.
It enters into human blood because of inhalation of polluted air, food and water though these are less relevant for assessing health hazards for humans than the amount of lead actually absorbed.
In a typical lead determination and after adding heparin, a natural anticoagulant, the blood is treated with trichloroacetic acid to precipitate proteins. These are then separated by centrifugation. In order to prevent interferences, lead is extracted within an organic solvent methyl isobutylketone (MIBK) after adding ammonium pyrrolidinedithiocarbamate (APDC) at pH 3. A lead is extracted as Pb (APCO)2. The organic phase is then aspirated into air-acetylene flame for the determination of lead. The detection limit of lead in blood is 0.1 µ g/mL. Most values of lead in blood are in the range 0.3- 0.4 µ g/mL with 0.6 µ g/mL as the upper limit. It is necessary that internal and external quality control should be used for the determination of lead in blood.