Quantification of Si in silicone oils by ICP-OES

A new simple and low cost method of quantification of trace amounts of silicon (Si) in silicone oils has been developed by combining the silicone emulsion and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. Silicone oils that contained phenyl groups in the viscosity range from 20 to 1000 mPa.s formed stable oil in water emulsions in the presence of Tween 80 surfactant and methylisobutylketone (MIBK). The Si in the emulsions was further quantified by ICP-OES. The calibration was performed using spiked inorganic silicon standard in the emulsions and the method was verified by the standard reference material SRM1066a. The precision and accuracy of the emulsion method applied to three phenyl containing silicone oils and polydimethylsiloxane (PDMS) with low viscosity (10 cSt) were good and acceptable (RSD < 10 % and the error range <10 %) with the limits of detection (LOD) in the emulsion as 0.5 ppm Si. Compared to the Si determination by the direct organic solvent ICP-OES, this method is much more convenient, where a regular ICP-OES instrument can be directly used for the quantification of Si in the silicone oils obtained via extraction by organic solvents from plastics and other samples.