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Silicone |
Silicone
is the organosilicon polymer, most commonly polydimethylsiloxane. Silicones are widely used in plastics, lubricants, hydraulic fluids,
antifoaming agents, and cosmetics to name a few.
Silicon (no "e") refers to the element in any form, most commonly found as silica or silicate minerals. |
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Total dissolved silicon can be determined using ICP or AA. If the material is an insoluble solid, total silicon can be determined by x-ray fluorescence. But because silicates are ubiquitous, these techniques are not good alternatives for measuring silicone, the organosilicon polymer. |
Silicon, SiSilica, SiO2 (sand, quartz)
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Analysis of SiliconesSilicones present in percent levels can easily be identified by infrared spectroscopy. However, determining trace amounts (ppm) of silicone is a different story. For several years we have been using a method adapted from Dow Corning (see L.G. Mahone, et al., Env. Tox. Chem. 1983, 307-313 and J.J. Kennan, et al., |
Anal. Chem. 1999, 71, 3054-3060) for low molecular weight silicones in wastewater. Polydimethylsiloxane can be hydrolyzed in strong acid and derivatized to give a product analyzed by gas chromatography. This analysis is only offered to industrial clients as we have discontinued offering the test for breast milk or tissues for individuals. |
| While this test can detect low molecular weight silicones in water >10 ppm, most silicone oils used in industry are high molecular weight and water insoluble. As such, this test usually gives negative results for water known to have been in contact with silicone. There are water soluble forms of silicone. Simethicone is a water soluble form used in antacids and other drugs to break up gas in the stomach. In fact Simethicone is used to calibrate the test above. |
GCMS of Water ExtractsBy extracting large volumes of water (up to 1 L) and concentrating the extracts, ppb-ppm levels of low molecular weight silicones can be determined in aqueous solutions. The chromatogram below shows silicone oligomers in the range of n=3-17. Note the drop in concentration with molecular weight reflects their relative water solubility. |
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