Pipette a well-mixed acid-preserved water sample to a flask or beaker. (Preservation must be by HNO3 (sp gr 1.42) to a pH of 2 or less immediately at the time of collection, normally about 2mL/L of HNO3 )

Add conc. Nitric Acid to the sample.

Place beaker on a hot plate and cover with watch glass.

Heat to evaporate until a small amount is left. ( Make sure sample do not boil and sample is not allowed to go dry or evaporate completely.

Remove from hot plate and allow to cool.

Add conc Nitric Acid then place beaker again on hot plate.

Continue heating making sure digestion is complete ( this is when sample becomes light in color or it does not change with continued heating.)

Heat to evaporate until a small amount is left.

Add (50%) Hydrochloric Acid to the sample.

Heat for about 15 min to make sure all residues or precipitates are dissolved.

Remove from hot plate and allow to cool. Wash insides of beaker and watch glass with water.

Filter the digestate to remove any insoluble material ( Since this could clog the nebulizer )

Transfer filtrate with rinsings to a volumetric flask.

Run the metal standard in the AAS and measure the linear regression (LR). Atleast 3 different concentrations of the standard must be measured.

Read the Lead content of each sample in the Atomic Absorption Spectrophotometer

Calculate concentration of Lead in sample using Linear Regression.


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