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

Arsenic (As)

• Avoid using dry ashing for sample preparation. Loss during sample preparation as the volatile oxide (As₂O₃ bp 460 °C) or chloride (AsCl₃ bp 130 °C) can be avoided by performing closed vessel digestions (EPA Methods 3051 and 2052), acid digestions under reflux conditions (EPA Method 3050B, Nitric and Perchloric Acid Digestions) or by caustic fusion using either sodium carbonate or sodium peroxide/sodium carbonate fluxes.
• Approach ICP-OES and ICP-MS determinations with caution. ICP-OES suffers from poor sensitivity and spectral interference issues and ICP-MS from the ⁴⁰Ar³⁵Cl mass interference (other interferences include ⁵⁹Co¹⁶O, ³⁶Ar³⁸Ar¹H, ³⁸Ar³⁷Cl, ³⁶Ar³⁹K, ¹⁵⁰Nd²⁺, and ¹⁵⁰Sm²⁺) on the monoisotopic ⁷⁵As. The use of atomic absorption using either the hydride generation or the graphite furnace techniques is very popular, although the use of 'reaction cells' that appear to eliminate the ⁴⁰Ar³⁵Cl interference in ICP-MS is an option worth exploring.

• As elemental data

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