Common Problems with Ag, As, S, Ba, Pb and Cr

Lead (Pb)

Lead has a number of chemical compatibility issues. In trace analysis the analyst typically does not experience serious problems unless attempting to combine Pb with sulfate or chromate. Other chemical components to avoid are the halogens (Cl, F, Br, and I), thiosulfate, arsenate, and sulfide to name the most common. However, the major problem with trace Pb analysis is contamination from the apparatus and atmosphere. Pb is used in industry in plumbing (pipes), solder, gasoline (significantly curtailed), drying agent for oils, glass, plumber's cement, covering of steel to prevent rust, as a pigment in paint (significantly curtailed), hair dye and as a pigment in plastics.

• Environmental contamination from airborne particulates is still a major concern in certain regions/laboratories depending upon location and age. When tetraethyl lead was widely used as an octane booster it was impossible to avoid environmental contamination in an open digestion apparatus. Open digestions in hoods where large volumes of air pass over the apparatus are of most concern. Closed container digestions or clean rooms / hoods are suggested to avoid this source of contamination.
• Avoid the use of any type of glass in sample preparations for Pb. Use quartz or fused silica and perform a sufficient number of blanks to define the degree of contamination.
• Avoid the use of any plastic with an inorganic pigment. Here Pb is only one of many concerns.
• Teflon containers should be carefully leached with dilute nitric acid before use and blanks performed to confirm freedom from Pb contamination. Be particularly suspicious of Teflon that has been used in sample preparations where Pb was a major, minor or trace component.

• Pb elemental data

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