Determination of Tin in Biological Materials by Atomic-Absorption Spectrometry with a Graphite Furnace

The determination of tin in the blood, liver, kidney, and spleen by atomic-absorption measurement using a graphite furnace was investigated. The presence of 20 micrograms/mL Fe(III) reduced absorbance of 0.2 microgram/mL Sn to 50%. To remove the interference of Fe(III), it was reduced to Fe(II) by 10% ascorbic acid, and Sn(IV) was extracted by methylisobutylketone (MIBK) without a chelating agent. This technique can be applied when 100 micrograms/mL Fe coexists with 0.2 microgram/mL Sn. Four methods for determination of tin in the blood were examined: (a) standard addition, (b) low-temperature ashing/MIBK extraction, (c) wet ashing/MIBK extraction, and (d) direct determination. The results of (a), (b), and (c) showed a high correlation (r greater than 0.86, n = 12), while the values obtained by (d) were scattered widely and showed little correlation with those determined by the other three methods. In methods (b) and (c), the detection limit was 10 ng/mL (0.2 ng Sn) without expansion mode, 2 ng/mL (0.04 ng Sn) with X 5 expansion mode, the recovery more than 90%, and the coefficient of variation 6.6% (n = 8). Method (c) was recommended for large sample sizes, and was also suitable for determination of tin in liver, kidney, and spleen, using 0.5%, instead of 10%, ascorbic acid.