Environmental Contamination

Reducing Environmental Contamination

Use the chemical blank as the performance criteria. Dealing with environmental contamination is expensive. Therefore, reduce the blank to the lowest possible value by eliminating contamination from the sample container, the chemist, and sample preparation apparatus. Achieve this by doing the following:

• Separate the sample preparation and handling area from all other areas.
• Eliminate as many foreign objects as possible from the preparation area (i.e. - Motorized objects such as stirring plates).
• Use all-plastic hoods.
• Keep the sample out of the hood area as much as possible.

The effect of the laboratory atmosphere on lead blank levels is shown in Table 8.1.

Hoods, which enhance atmospheric exposure and hence contamination, are necessary for the safety of the analyst. Atmospheric contamination has been reduced significantly through the use of "clean rooms" that use HEPA filtered air. HEPA (High Efficiency Particulate Air) filters are 99.99 % efficient in removing particulates down to 0.3 µm.

A Positive Pressure Filtered Air "Clean" Room is shown in the following architectural diagrams.

Diagram 8.1: Clean Room Layout (Top View)

Diagram 8.2: Clean Room Layout (Front View)

Diagram 8.3: Clean Room Layout (Side View)

The effectiveness of clean rooms in eliminating environmental contamination is illustrated in Tables 8.2 and 8.3 which show a significant reduction in the blank.

For budgets that cannot handle the cost associated with clean room facilities there have been several ingenious designs that are effective in dealing with environmental contamination. Diagram 4.4 illustrates some of these designs using equipment that is relatively inexpensive and easily obtained.

Diagram 8.4: Evaporation Chamber Designs¹

Was this helpful?  Tell a Friend | Let us know