Methodology

Sample Preparation :

For Wet Paint , spread onto a clean glass plate a thin layer and allow to dry inside a conventional oven. When dry , scrape out the paint and cut into small pieces.

For paint coated on product , remove coating from item using a stainless steel razor blade or by using acetone or any suitable solvents.

Digestion & Analysis :

Weigh dried sample into a beaker.

Add conc. HNO3 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 6N 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 about 10 ml of digestate remains.

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

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

Transfer filtrate with rinsings to a volumetric flask.

Run the Lead standard solutions 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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EN 71 Part 3 ( Testing Procedure )