Antimony (Sb) is the fourth element in Group VA in the periodic table. It has an atomic number of 51, an atomic weight of 121.75, and valences of 3 and 5. The average abundance of Sb in the earth’s crust is 0.2 ppm; in soils it is 1 ppm; in streams it is 1 μg/L, and in groundwaters it is <0.1 mg/L. Antimony is sometimes found in native form, but more commonly as an ore, stibnite (Sb2S3). It is used in alloys of lead and in batteries, bullets, solder, pyrotechnics, and semiconductors.
The common aqueous species are Sbo2−, HSbO2, and complexes with carbonate and sulfate. Soluble salts of antimony are toxic. The U.S. EPA primary drinking water standard MCL is 6 μg/L.
The electrothermal atomic absorption spectrometric method (Section 3113 B) or the inductively coupled plasma mass spectrometric method (Section 3125) are the methods of choice because of their sensitivity. Alternatively use the flame atomic absorption spectrometric method (Section 3111 B) or the inductively coupled plasma method (Section 3120) when high sensitivity is not required.