Tin (Sn) is the fourth element in Group IVA in the periodic table. It has an atomic number of 50, an atomic weight of 118.69, and valences of 2 and 4. The average abundance in the earth’s crust is 2.1 ppm; in soils it is 10 ppm; in streams it is 0.1 μg/L, and in groundwaters it is <0.1 mg/L. Tin is found mostly in the mineral cassiterite (SnO2), in association with granitic rocks. Tin is used in reducing agents, solder, bronze, pewter, and coatings for various metals.
The common aqueous species are Sn4+, Sn(OH)4, SnO(OH)2, and SnO(OH)3−. Tin is adsorbed to suspended solids, sulfides, and hydroxides. Tin can be methylated in sediments. Tributyl tin undergoes biodegradation quickly. Organo-tin compounds are toxic. Tin is considered nonessential for plants and animals.
Either the flame atomic absorption method (Section 3111 B) or the electrothermal atomic absorption method (Section 3113 B) may be used successfully for analyses, depending upon the sensitivity desired. The inductively coupled plasma mass spectrometric method (Section 3125) also may be applied successfully in most cases (with lower detection limits), even though tin is not specifically listed as an analyte in the method.