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Melissa Eubanks- Analytical Problem- Silicones in Cosmetics


I want to explore whether the silicone, commonly referred to as cyclomethicone, used in cosmetic products is harming the marine environment. Originally methylcyclotetrasiloxane, aka D4, was used in cosmetics but it was found that it was washing off skin and hair and building up the marine environment. So decamethylcyclopentasiloxane, aka D5, replaced D4 in cosmetics. Decamethylcyclopentasiloxane is a volatile that is released to the atmosphere in large quantities (2). There are also concerns that D5 is accumulating in the marine environment.

This is an important issue because D5 is used in many cosmetic products and is just being washed down the drain, it is not toxic to humans but it is possible that its harming the marine environment (1). There are other alternatives to using D5 but manufactures of the cosmetics are concerned that their products won't give consumers the same results without the D5 and that their profits would decline.

The hypothesis is that D5 is harming marine environment because it is accumulating, and even in its purified form there are residual levels of D4, that are harming marine organisms (1).

The main analyte to be focused on is decamethylcyclopentasiloxane but methylcyclotetrasiloxane will also be looked at to determine if there are toxic levels of D4 present in D5. The matrix where D5 could be found is the water where a lot of drain water is deposited without treatment, as well as marine organisms.

1). Reisch, M. Storm Over Silicones. C&EN Northeast News Bureau 2011, 89, pp 10-13.

2). McLachlan, M.; Kierkegaard, A.; Hansen, K.; Van Egmond, R.; Christensen, J.; Skjøth, C. Concentrations and Fate of Decamethylcyclopentasiloxane (D5) in the Atmosphere. Environ. Sci. Technol 2010, 44 (14), pp 5365-5370.


UV-Vis absorption spectrometry

I could not find any articles defining the maximum wavelengths of absorption for decamethylcyclopentasiloxane. I do not believe that it has a UV-vis range and I could only find information about the use of NMR, IR, Mass Spec, and GC for the determination of D5.


Similar Analytical Problem:

Chuxin Chen's analytical problem is the comparative analysis of arbutin and tranexamic acid in skin whitening products. The hypothesis is tranexamic acid has better performance in skin whitening and more reliable to use externally. This analytical problem is relevant because the use of skin whitening creams is increasing and there seems to be a difference in price and effectiveness of the product according to which compound it contains. The analytical problem is similar to my problem in that we are both targeting a specific compound found in cosmetics and personal care products. Both analytical problems are concerned with the health risks but mine focuses on the environmental aspect while Chuxin's problem focuses on the use of the skin whitening products by humans and those risks. The matrices are different; Chuxin will be looking at the skin creams, while I'll be targeting the sediment and aquatic life to find the concentration of D5.


Hypothesis:Decamethylcyclopentasiloxane is washing off skin when used in cosmetic products and accumulating in the aquatic life.

Studies: (A) Identify regions that contain D5 and/or water treatment plants that are not taking D5 out of the water. Determine if there is a difference in levels of D5 in fish and sediment correlating to the distance from the source of D5. (B) Measure the concentration of D5 in water found to contain D5. (C) Based on concentrations found in the water, do a study to see if there is a higher concentration of D5 in the fish and sediment, therefore showing an accumulation.

Alternative Studies: If there is not a high concentration of D5 in the water and aquatic life, then determine concentration in air because D5 is a volatile cyclic methylsiloxane.

The concentration of D5 found in sediment ranged between 60-260 ng/g (d.w.). The concentration of D5 in ragworms was 51-760 ng/g (McLachlan).


McLachlan, M.; Kierkegaard, A.; Hansen, K.; Van Egmond, R.; Christensen, J.; Skjøth, C. Concentrations and Fate of Decamethylcyclopentasiloxane (D5) in the Atmosphere. Environ. Sci. Technol 2010, 44 (14), pp 5365-5370.


BLOG 5: Fluorescence

D5 is not fluorescent; it does not have a rigid structure, which is favored by fluorescence. Fluorescence is found in compounds that have aromatic functional groups with low energy pi-pi transitions and D5 does not contain aromatic compounds. D5 can be observed using infrared spectrometry, and a range of bands can be seen from 1264-808cm-1. A strong band can be seen at 1263cm-1 while a peak correlating to the SiO species can be found at 1224cm-1 (Almond).

Almond, M. Becerra, R. Bowes, S. Cannady, J. Ogden, S. Young, N and Walsh R. A Mechanistic Study of the Low Pressure Pyrolysis of Linear Siloxanes. Physical Chemistry Chemical Physics. 2008, 11, 6856-6861.

View image1

Decamethylcyclopentasiloxane, Single-Component Organic Standards can be purchased online from SPEX CertiPrep2
Catalog Number: S1110
Conc.: 1000µg/mL
1mL for $26

1.) http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO|BRAND_KEY&N4=444278|ALDRICH&N25=0&QS=ON&F=SPEC
2.) http://www.spexcertiprep.com/products/product_organic.aspx?part=S-1110


BLOG 7

Decamethylcyclopentasiloxane
Nominal Mass: 370
Exact Mass: 370.773

Two Types of Mass Analyzers that can be used to Quantify D5:
Electron Impact Ionization- TOF2
ICP-TOF1

mass spec D5.JPG2

This is a mass spec of D5 using Electron Impact Ionization and Time of Flight mass analyzer.
Conditions:
Gas-liquid chromatography mass spectrometry was carried out on the polymerisation reaction mixture using an AE1 MS-902 double focusing mass spectrometer. Column conditions: 3 ft x in. 0.d. glass column; 23 % OV-17 on Chromasorb G; column temperature programmed from 60 to 260 "C at 6 "C/min; 50 ml/min Helium carrier gas. Mass spectra were obtained with electron energies of 70 eV; accelerating potential, 8 kV; trap current, 100 PA; source temperature, 250 "C.


1.) Dong, X.; Proctor, A. Characterization of Poly(dimethylsiloxane)s by Time-of-Flight Secondary Ion Mass Spectrometry. Macromolecules, 1997, 30, 63-70.

2.) Pickering, G.; Oliff, C.; Rutt, K., The Mass Spectrometric Behaviour of Dimethylcyclosiloxanes. Organic Mass Spectrometry. 1975, 10, 1035-1045.

Comments

BLOG 13

D5 is not electroactive, but I did find information about the electrochemical oxidation of deca-n-propylcyclopentasilane, which when oxidized forms decamethylcyclopentasiloxane.

A Nicolet 5ZDX FT-IR spectrometer; Finnigan 4020 Quadrupole mass spectrometer and a Bruker WP 200 SY
NMR spectrometer were used to characterize the analytes because mixtures of different anayltes were created during the oxidization of deca-n-propylcyclopentasilane.

For the electrochemical measurements a Princeton Applied Research potentiostat was used.

Cyclic voltammograms were measured using different working electrodes: polished Pt button; polished glassy carbon; graphite rod.

Electrolyses were controlled at a potential of
1.1 to 1.2V on Pt foil or graphite rod.

Backera, J.; Shena,M.; Westb, R. Electrochemical oxidation of deca-n-propylcyclopentasilane [(n-Pr) 2Si]5, dodecamethylcyclohexasilane (Me2Si) 6 and tetradecaethylcycloheptasilane (Et2Si) 7. Journal of Electroanalytical Chemistry, 417, 1996, pp 77-82.

Blog 9? (-1 pt).
Blog 10. OK.
Blog 11 (1 pt).

The preferred technique to investigate my analytical problem is Gas Chromatography coupled with Mass Spectrometry. I have a volatile compound so GC works well and MS can tell me if the D5 is accumulating in the sediment and aquatic life.

Nur Marzuki will also be using GC/MS for the quantification of Liquefied Petroleum GAS in insecticide aerosol; to control the amount of the insecticide used and proper health precautions can be taken.

Lauren Sauer will be using GC/FTMS while trying to detect trichloroethylene and tetrachloroethylene in the vapor forms.

Good answers.

Preparing Sediment for Analysis as raw extract (1):

Top layer (1-2 cm) of undisturbed sediment will be collected.

1. Extraction by Sedimentation: 10g of dewatered sediment will be extracted with 10mL acetone and 2ml pentane.

2. Centrifugation: The liquid phase will be separated from the solid by centrifugation. The extraction and centrifuge will be repeated with remaining solid phase. Liquid phases from extraction and centrifugation will be combined.

3. Wash: 20mL of purified water will be added to the liquid phases.

4. Centrifugation: Liquid phases will be separated from remaining large particles.


1.) Kierkegaard, A.; van Egmond, R.; McLachlan, M. S; Cyclic Volatile Methylsiloxane Bioaccumulation in Flounder and Ragworm in the Humber Estuary. Environmental Science and Technology. 2011, 5936-5942.

Blog 6. Good answers.
Blog 7. What are the ionization sources that you are using? You mention as part of the mass spectrometer, but do identify them as sources. (-0.1 pt)

Both answers for Blogs 4 and 5 are good.

D5 is not fluorescent; it does not have a rigid structure, which is favored by fluorescence. Fluorescence is found in compounds that have aromatic functional groups with low energy pi-pi transitions and D5 does not contain aromatic compounds. D5 can be observed using infrared spectrometry, and a range of bands can be seen from 1264-808cm-1. A strong band can be seen at 1263cm-1 while a peak correlating to the SiO species can be found at 1224cm-1 (Almond).


Almond, M. Becerra, R. Bowes, S. Cannady, J. Ogden, S. Young, N and Walsh R. A Mechanistic Study of the Low Pressure Pyrolysis of Linear Siloxanes. Physical Chemistry Chemical Physics. 2008, 11, 6856-6861.

My analytical problem is similar to Melissa's since we have similar matrix, the cosmetics and skincare products, and we both want to analyze our analytes which are undetectable under UV-Vis. The difference is, Melissa's research concerns about the evironmental aspect of the silicone accumulation from the cosmetics, mine is focus on the skin whitening effect of the two analytes.

BLOG 2, what about Question 5a or 5b? Possible absorption due to its molecular features? Indirect UV-VIS detection or derivatization? (-0.3 pt)

BLOG 3, what studies are different? What studies are similar? (-0.5 pt).

Great posting!