Sensitive Method for Quantification of Octamethylcyclotetrasiloxane (D4) and Decamethylcyclopentasiloxane (D5) in End-Exhaled Air by Thermal Desorption Gas Chromatography Mass Spectrometry

Octamethylcyclotetrasiloxane (D4) and decamethylpentasiloxane (D5) are used as ingredients for personal care products (PCPs). Because of the use of these PCPs, consumers are exposed daily to D4 and D5. A sensitive analytical method was developed for analysis of D4 and D5 in end-exhaled air by thermal desorption gas chromatography mass spectrometry (TD-GC-MS), to determine the internal dose for consumer exposure assessment. Fifteen consumers provided end-exhaled air samples that were collected using Bio-VOC breath samplers and subsequently transferred to automatic thermal desorption (ATD) tubes. Prior to use, the ATD tubes were conditioned for a minimum of 4 h at 350 degrees C. The TD unit and auto sampler were coupled to a GC-MS using electron ionization. Calibration was performed using 0-10 ng/mu L solutions of D4/D5 and C-13-labeled D4/D5 as internal standards. The ions monitored were m/z 281 for D4, 355 for D5, 285 for C-13-labeled D4, and 360 for C-13-labeled D5. The addition of internal standard reduced the coefficient of variation from 30.8% to 9.5% for D4 and from 37.8% to 12.5% for D5. The limit of quantification was 2.1 ng/L end-exhaled air for D4 and 1.4 ng/L end-exhaled air for D5. With this method, cyclic siloxanes (D4 and D5) can be quantified in end-exhaled air at concentrations as low as background levels observed in the general population.