Determination of silicon in serum and tissue by electrothermal atomic absorption spectrometry

Objectives: To employ an electrothermal atomic absorption spectrometry (ETAAS) method with chemical modifiers for the determination of silicon (Si) in serum and tissues. Methods: Si was measured in serum of chronic hemodialysis patients, and in fibrous breast capsule tissues following silicone-gel implant removal. Tissue was dried, and digested with concentrated nitric acid prior to analysis. A chemical modifier, which included lanthanum oxide and ammonium phosphate, was used to dilute the serum, and digested tissue samples (1:4) before atomization. Si was determined at 251.6 nm in a graphite furnace using an atomic absorption spectrophotometer. Results: The method was linear (to 1000 μg/L), and precise (CV 5.9% at 281 μg/L and 8.4% at 73 μg/L). Recovery of Si in spiked serum and breast tissue samples was between 97–104%. Reference values for women on a normal diet and no exposure to silicone implants gave serum Si of 30 to 209 μg/L (n = 60), and breast tissue levels of 0.25 to 2.4 μg/g dry wt (n = 48). Si in breast capsule from women exposed to silicone breast implants varied from 29 to 496 μg/g dry wt (n = 10). Serum Si in hemodialysis patients (n = 53) ranged from 900 to 3300 μg/L. Conclusions: We conclude that our chemically modified ETAAS method is suitable for Si determination in normal and elevated human serum and tissue specimens.