Detection and characterization of poly(dimethylsiloxane)s in biological tissues by GC/AED and GC/MS

We have developed a sensitive method for the detection, characterization, and quantitation of low molecular weight silicones using gas chromatography coupled with atomic emission detection (GC/AED) and gas chromatography/ mass spectrometry (GC/MS). Using this approach, we have detected 12 distinct silicon-containing peaks in PDMS-V poly(dimethylsiloxane) oil by GC/AED, and we have used GC/MS analysis to identify some of the abundant peaks by MS spectral matching. Polydimethylpolysiloxanes contain 37.8% silicon; therefore, the amount of poly(dimethylsiloxane) in each peak can be calculated from its silicon content. The first three GC peaks from PDMS-V were identified as dodecamethylpentasiloxane, tetradecamethylhexasiloxane, and hexadecamethylheptasiloxane using Wiley Mass Spectral Library match (> 90%). Peaks 4-12 could not be matched unequivocally with the spectral library but showed ionic fragments characteristic of PDMS (73, 147, 221, 281, 295, and 369 amu). The detection limit for silicones using GC/AED and GC/MS systems was found to be 80 and 10 pg/microL, respectively. Studies were conducted using mouse liver homogenates spiked with varying amounts of PDMS-V, and the recovery was found to be greater than 90% over a wide range of PDMS-V concentrations. This method appears to work equally well for both linear and cyclic poly(dimethylsiloxane)s. Thus, the methodology described here has the potential to allow the measurement of less than 1 microgram of silicone/g of biological tissue. The overall goal of this research is to establish and validate a methodology by which the unequivocal identification and quantitation of poly(dimethylsiloxane)s can be accomplished.