ABSTRACT
In addition, argon can form polyatomic interferences with elements found in the acids used to dissolve the sample. For example, in a hydrochloric acid medium, 40Ar+ combines with the most abundant chlorine isotope at 35 amu to form 40Ar35Cl+, which interferes with the only isotope of arsenic at mass 75, whereas in an organic solvent matrix, argon and carbon combine to form 40Ar12C+, which interferes with 52Cr+, the most abundant isotope of chromium. Sometimes, matrix or solvent ions combine to form spectral interferences of their own. A good example is in a sample that contains sulfuric acid. The dominant sulfur isotope, 32S+, combines with two
oxygen ions to form a 32S16O16O+ molecular ion, which interferes with the major isotope of Zn at mass 64. In the analysis of samples containing high concentrations of sodium, such as seawater, the most abundant isotope of Cu at mass 63 cannot be used because of interference from the 40Ar23Na+ molecular ion. There are many more examples of these kinds of polyatomic and molecular interferences, which have been comprehensively reviewed.1 Table 14.1 represents some of the most common matrixsolvent spectral interferences seen in ICP-MS.
