Brothers H M, Boehmer T, Campbell R A, Dorn S, Kerbleski J J, Lewis S, Mund C, Pero D, Saito K, Wieser M, Zoller W
Analytical Sciences Department, Dow Corning Corporation, P.O. Box 994, Midland, MI, 48686-0994, USA.
Evonik Nutrition & Care GmbH, Goldschmidtstrasse 100, Essen, 45127, Germany.
Int J Cosmet Sci. 2017 Dec;39(6):580-588. doi: 10.1111/ics.12411. Epub 2017 Aug 15.
Organosiloxanes are prevalent in personal care products (PCPs) due to the desired properties they impart in the usage and application of such products. However, the European Chemical Agency (ECHA) has recently published restriction proposals on the amount of two cyclic siloxanes, octamethylcyclotetrasiloxane (D4) and decamethylcyclotetrasiloxane (D5), allowed in wash off products such as shampoos and conditioners which are discharged down the drain during consumer use. This legislation will require that reliable analytical methods are available for manufacturers and government agencies to use in documenting compliance with the restrictions. This article proposes a simple analytical method to enable accurate measurement of these compounds down to the circa 0.1 weight per cent level in PCPs.
Although gas chromatography methods are reported in the literature for quantitation of D4 and D5 in several matrices including PCPs, the potential for generation of false positives due to contamination, co-elution and in situ generation of cyclic volatile methylsiloxanes (cVMS) is always present and needs to be controlled. This report demonstrates the applicability of using a combination of emulsion break, liquid-liquid extraction and silylation sample preparation followed by GC-FID analysis as a suitable means of analysing PCPs for specific cVMS.
The reliability and limitations of such methodology were demonstrated through several round-robin studies conducted in the laboratories of a consortium of silicone manufacturers. In addition, this report presents examples of false positives encountered during development of the method and presents a comparative analysis between this method and a published QuEChERS sample preparation procedure to illustrate the potential for generation of false positives when an inappropriate approach is applied to determination of cVMS in personal care products.
This report demonstrates that an approach to determine cVMS levels in personal care products is to perform an emulsion break on the sample, isolate the non-polar phase from the emulsion break and treat with a silylation reagent to abate potential in situ formation of cyclics during the course of GC-FID analysis. Round-robin studies conducted in laboratories representing multiple siloxane manufacturers demonstrated the reliability of the GC-FID method when measuring cVMS in PCPs down to circa 0.1%.
有机硅氧烷因其能赋予个人护理产品（PCP）理想的使用性能而广泛应用于此类产品中。然而，欧洲化学品管理局（ECHA）最近发布了关于洗发水和护发素等冲洗型产品中八甲基环四硅氧烷（D4）和十甲基环五硅氧烷（D5）这两种环状硅氧烷允许使用量的限制提案，这些产品在消费者使用后会通过下水道排放。该法规将要求制造商和政府机构拥有可靠的分析方法，用于记录是否符合相关限制。本文提出了一种简单的分析方法，能够在PCP中准确测量这些化合物，检测限约为0.1%（重量）。
尽管文献中报道了气相色谱法用于定量包括PCP在内的多种基质中的D4和D5，但由于污染、共洗脱以及环状挥发性甲基硅氧烷（cVMS）的原位生成导致假阳性结果的可能性始终存在，需要加以控制。本报告展示了采用破乳、液 - 液萃取和硅烷化样品制备相结合，随后进行气相色谱 - 火焰离子化检测（GC - FID）分析，作为分析PCP中特定cVMS的合适方法的适用性。
通过在多家有机硅制造商组成的联盟实验室进行的多次循环研究，证明了该方法的可靠性和局限性。此外，本报告列举了方法开发过程中遇到的假阳性实例，并对该方法与已发表的快速、简便、廉价、有效、耐用且安全（QuEChERS）样品制备程序进行了对比分析，以说明在个人护理产品中测定cVMS时，采用不恰当方法可能产生假阳性的情况。
本报告表明，测定个人护理产品中cVMS含量的一种方法是对样品进行破乳，从破乳后的乳液中分离出非极性相，并用硅烷化试剂处理，以减少在GC - FID分析过程中原位生成环状物的可能性。在代表多家有机硅制造商的实验室进行的循环研究表明，当测定PCP中的cVMS含量低至约0.1%时，GC - FID方法具有可靠性。
