Contamination From the Analyst and Apparatus

Part 8, Environmental Contamination, discussed the importance of a clean room to reduce air contaminants while performing trace analyses. A clean room is equally important for minimizing contamination from the analyst.

Contamination From the Analyst

The area pictured in figure 10.1 is the buffer zone between the outside air and the main clean room. Air entering with the analyst is filtered (at the rate of 1.5 times per minute) before the analyst enters the main clean area. A cart contains a HEPA vacuum used for cleaning objects to be taken into the main clean room. A ‘sticky mat' on the floor just inside the room will remove shoe dust and other contaminants. Another sticky mat (not pictured) is placed just before the entry way to the buffer zone.

Fig. 10.1: Entering the Clean Room

The analyst pictured here is wearing disposable "clean room" clothing. There are three separate pieces (head covering, foot covering, and main coverall). The clothing is worn over normal street clothes and should never leave the clean room area.

Common Contaminants

• Sweat contains Ca, Mg, Pb, K, NH₄⁺ , SO₄^-2, PO₄^-3, and Cd (for those who smoke).
• Cosmetics can contain high concentrations of Al, Be, Ca, Cu, Cr, K, Fe, Mn, Ti, and Zn.
• Some hair dyes contain Pb(OAC)₂.
• Dandruff shampoo can contain significant levels of Se.
• Eye make-up may contain Hg as a preservative.
• Calamine lotion is almost pure ZnO.
• Watches and jewelry contain an assortment of elements and should not be worn in the laboratory.

Analyst Tips

• Keep the volume of reagents to a minimum.
• Keep sample preparation and measurement times to a minimum (use timers and don't let a digestate sit overnight or even during a lunch break).
• Keep a history of beakers and other apparatus as to chemical exposure.
• Exercise care in handling reagents (exposure to atmosphere or pouring liquid back into the same container or into the wrong container can result in serious contamination).
• Disposable powder-free gloves prevent contamination from earlier exposures as opposed to reusable gloves (vinyl is better for difficult manipulations such as pipeting and handling wet glassware while latex is more rugged).
• Disposable laboratory coats prevent contamination from earlier exposures.
• Disposable foot coverings keep any dirt that the ‘sticky mat' missed contained.

TIP: Dangerous operations require appropriate laboratory clothing REGARDLESS of the potential for contamination.

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