measurement of silisone deposition by various analytical method

8/7/2019 measurement of silisone deposition by various analytical method

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Measurement of Silicone Deposited on Hair

by Various Analytical Methods

Poster presented at the 19th IFSCC Congress, Sydney

22 - 25 October 1996

A. De Smedt, I. Van Reeth, S. Marchioretto, Dow Corning SA, Brussels, BelgiumD.A. Glover, Dow Corning Corp. Midland, Michigan

J. Naud, University of Louvain, Louvain-La-Neuve, Belgium


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by Various Analytical Methods

A. De Smedt, I. Van Reeth, S. Marchioretto, Dow Corning SA, Brussels, Belgium

D. A. Glover, Dow Corning Corp. Midland, MichiganJ. Naud, University of Louvain, Louvain-La-Neuve, Belgium

AbstractSilicones, commonly used as conditioning agents in 2-in-1 shampoos, are already effective at very

low levels. To date, no single analytical method has been identified as ideal for quantifying these

deposits on hair.

Methods currently described in the literature are Fourier transform infrared DRIFT

spectroscopy (FT-IR DRIFT) and atomic absorption (AA). However, both methods have

limitations. The FT-IR detection limit is quite high, and the accuracy of AA measurements is

strongly influenced by the efficacy of the extraction step.

A broad literature search has been carried out in order to cross-fertilise with different areas of

analytical chemistry and possibly generate new ideas about screening tests for small amounts ofsilicone deposited on hair. The current study describes an evaluation of new methods which

complement each other very well.

l An innovative X-ray fluorescence (XRF) method that characterises bulk hair. XRF methods

already have been described in the literature as means of analysing trace elements such as

copper, cobalt, or nickel within the hair shaft, Prior to this study, these methods had not

been used to document the presence of conditioning agents including silicone. Moreover,

the sample preparation proposed in this study includes a pyrolysis step at 700C, ensuring

homogeneity of the analysed sample.

l A wettability measurement method that characterises single hair fibre surface by assessing its

hydrophilicity or hydrophobicity.

IntroductionKnowing the amount of conditioning agents deposited on hair surface by shampoos or

conditioners is vitally important for cosmetic chemists. It allows them to study the absorptivity of

polymers/surfactants on the hair surface, to correlate absorptivity with sensory properties, and

also to greatly facilitate claim substantiation (European Cosmetic Directive 6th Amendment).

However, as the levels of conditioning agents are usually very low, accurate data are very difficult toget.

Silicones possess a range of unique properties like lubricity, low solubility parameter, low

intermolecular forces, water insolubility, and a very low surface tension, such that they spread

easily on most surfaces to give a uniform, smooth, hydrophobic film (Todd and Hayes, 1971;

Starch, 1984). This explains why silicones have been used for years as superior conditioning

agents, even at very low deposition levels (e.g., Bergman and Bess, 1991). The following benefitsare well described in the literature:

l Silicones replace the conditioning benefits of the sebum which is being removed from the

hair during shampooing, with no oily feel.

l Silicones provide a smooth, silky and not tacky feel, and excellent detangling and

compatibility performance (e.g., Yahagi, 1992). They are also gloss enhancers.

l Silicones reduce the damage associated with oxidative treatments such as straightening or

permanent waving (Berthiaume et al., 1994, 1995).

l Silicones also help the spreading of other active ingredients (Alexander, 1992), ensuring a

better film homogeneity, and may retard the rate of sebum spreading (Bogardus et al.,

1985).

Silicone polymers especially effective in conditioning shampoos are high molecular weight

dimethicones, dimethicone copolyols, and amodimethicones.


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Measurement ofSilicone Deposited on Hair

Because silicones are very commonly used ingredients in conditioning shampoos, many studies

have been carried out in an attempt to quantify silicone deposition on hair. Atomic absorption

(AA), and to a lesser extent Fourier transform infrared DRIFT spectroscopy (FT-IR DRIFT), are

very popular and in many cases, the best option. However, the FT-IR DRIFT detection limit is

quite high, and AA is not really suitable for the analysis of organofunctional or crosslinked

polymers, due to the lack of efficiency of the extraction method.

Literature Search SummaryA broad literature search has been carried out in order to cross-fertilise with different areas of

analytical chemistry and possibly generate new ideas about screening tests of small amounts of

silicone deposited on hair. Information on analytical methods was gathered from the following

areas:

l Characterisation of uncoated hair

l Characterisation of conditioning agents other than silicone deposited on hair

l Characterisation of silicone deposited on substrates other than hair

l Characterisation of silicone deposited on hair

The analytical methods used to characterise hair composition can be divided into two

categories, depending on the kind of information generated:

l Surface and near-surface methods analyse only an extremely small portion of a hair fibre ata time (maximum 1 square micron, depending on the method).

l Bulk methods provide an average value of the analysed species for the hair tress, which is

more representative of the real value of the whole scalp.

The aim was to select one idea for bulk analysis, one for sample preparation, and one for

surface analysis.

Analysis of uncoated hairAnalysing bulk and surface composition of human hair is rather difficult due to their fibre

characteristic and natural heterogeneity. However, analysis of hair composition has generated a

great deal of interest from many disciplines, including environmental, epidemiological, and

forensic sciences. This interest has arisen primarily as a result of the following.

l The trace element levels in hair are considered as a possible quantitative indicator for their

levels in other parts of the body and for exposure of the person to various environmental

sources.

l Hair is easy to sample and handle, compared to human tissues.

During the last two decades, several hundred papers and books have been published

concerning hair composition analysis.

Analytical methods

The most commonly used analytical methods for hair composition analysis include the following

(Table 1):

l Surface/single fiber analysis: scanning electron microprobe (SEM/EDX), electron

spectroscopy for chemical analysis (ESCA), secondary ion mass spectroscopy (SIMS), atomic

force microscopy (AFM), particle-induced X-ray emission (PIXE), and Fourier-transform

infrared spectroscopy (FT-IR).l Bulk analysis: atomic absorption spectrometry (AA) and X-ray fluorescence (XRF). Some

work has also been initiated with neutron activation analysis (NAA).

l Ion chromatography (IC).

Hair sample preparation for bulk analysis

For bulk analysis of major elements or polymers, hair tresses do not require special sample

preparation. However, for bulk analysis of trace elements or polymers, the hair tresses need a

sample preparation step in order to ensure their homogeneity and to increase their trace

elements concentration. Several sample preparations are described in the literature (Table 2),

including: cryogenic grinding, pyrolysis, mineralisation by dry ashing, and solvent extraction.


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A. De Smedt et al.

Table 1. Analysis Methods.

Hair Coated With Silicone CoatedAnalytical Organic Conditioning Substrates Other

Method Uncoated Hair Agents Than Hair Silicone Coated Hair

Surface Analysis

SEM (EDX) Bottoms et al., 1972 Goddard and Schadt, Bergman and Bees 1991

Kanetake et al., 1992 1988 Sejpka, 1993Swift, 1991 Schmidt and Berthiaume et al., 1994,

Goddard, 1994 1995

Yahagi, 1992

ESCA Robbins et al., 1984 Goddard and Schadt, Smarajit, 1995

1988 Wendel and DiSapio,

Goddard and Harris, 19831987 (Berthiaume et al., 1994,

1995)

(Klimisch, 1991)

Pavlichko et al., 1994

Schmidt and

Goddard, 1994

Cipriano et al., 1994

FT-IR DRIFT Joy and Lewis, 1991 Klimish and Klimisch et al., 1987

Jurdana et al., 1994 Chandra, 1986, Bergman and Bees, 1991

(skin)

SIMS Braida et al., 1994

TOF-SIMS Berthiaume et al., 1995

PIXE Cortes Toro et al., 1993

Wu et al., 1993

Wettability Braida et al., 1994 Watanabe and Yahagi,

Kamath et al., 1984, 1995

1984,1985,1985,1987

Bulk AnalysisAA Cortes Toro et al., 1993 Bergman and Bees, 1991

Folin et al., 1991 Gooch and Kohl, 1988

Berthiaume et al., 1995

GC-MS Solka and Kocis, 1994

NAA Cortes Toro et al., 1993

XRF Havranek et al., 1989 Helliwell, 1994 (skin)Torok et al., 1984 paperEltayeb and VanGrieken, 1989

Volkov et al., 1994

Qi et al., 1986

Cortes Toro et al., 1993

Folin et al., 1991

Ion chroma- Sturaro et al., 1993

tography


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Table 2. Sample Preparation For Bulk Hair Analysis.

AnalyticalMethod

No-sample pre-

treatment

Cryogenic

grinding

Pyrolysis

Mineralisation by

dry ashing

Solvent

extraction

Uncoated Hair

Qi et al., 1986

Torok et al., 1984

Qi et al., 1986

Havranek et al., 1989

Volkov et al., 1994

Sturaro et al., 1993

Eltayeb and van

Grieken, 1989

Grooch and Kohl, 1988

Hair Coated With

OrganicConditioning Agents

Solka and Kocis, 1994

Holt, 1991

Silicone Coated

Substrates Other

Than Hair

Homer et al.,1960 (meat)

Silicone Coated

Hair

Klimisch et al.,

1987

Klimisch, 1991

Analysis of conditioning agents other than silicones deposited on hairSurface analytical methods used to determine non-silicone conditioning agents on hair are SEM,

ESCA, AFM, and SIMS (Tables 1 and 2). Radiochemical labelling has also been tried. Qualitative

and indirect assessment via wettability measurements or dye absorption have also been very useful

to characterise conditioned hair.

Analysis of silicone deposited on substrates other than hairSilicones are also applied at very low levels on substrates other than hair. Some of the methods to

characterise the deposit are silicon-specific (e.g., AA, XRF, radiochemistry, colorimetry, SEM);

some are silicone polymer-specific (IR, Raman, NMR, GC-MS, ESCA) (Tables 1 and 2).

When background levels of inorganic silicon are high or variable, a silicone-specific method or

physical separation of the silicone from the matrix prior to quantification (e.g., using solvent

extraction) is generally preferred.

l On skin, silicone has been analysed using FT-IR ATR (attenuated total reflectance)

(Klimisch and Chandra, 1987) or XRF. Helliwell (1994) has described how a tape can be

applied on the treated skin, then removed and analysed for Si by XRF.

l In food containing low natural inorganic Si (like meat), Homer et al. (1960) have

determined total Si down to 3 ppm by decomposing it with H 2S0 4 and HNO3, fusing with

Na2CO3, and testing the Si level via colorimetry.

l On paper, the amount of silicone deposited is determined by an XRF detection of inorganic

silicon.

Analysis of silicone deposited on hairSeveral methods and sample preparations listed above have also been used to

qualitatively/quantitatively characterise the silicone deposited on hair (Tables 1 and 2).

Surface analysis

FT-IR DRIFT correlates very well to AA data, but has a higher detection limit. Sample preparation

is usually cryogenic grinding. SEM/EDX and ESCA are also often cited in the literature. TOF-

SIMS and wettability studies have been initiated very recently.

Bulk analysis

By far, the most commonly used method to analyse the amount of silicone deposited on hair is AA

(Tables 1 and 2). This method usually includes an extraction step by a solvent like methyl isobutyl

ketone (Klimish, 1991). Its main advantages are speed and a fairly low detection limit. Its drawback

is poor recovery in solvent extraction, especially for crosslinked and amino-functional polymers.

Sonication or enzymatic breakdown of the hair structure (Grooch and Kohl, 1988) may

improve recovery.


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A. De Smedt et al.

SummaryBoth straightforward and very sophisticated methods have been developed to analyse coated and

uncoated hair. The most popular methods for bulk hair analysis are AA and XRF, and for surface

and near-surface analysis, SEM, ESCA, and wettability. Sample pretreatment for bulk analysis for

trace elements usually consists of solvent extraction, pyrolysis, and dry-ashing.

Although extensively and successfully developed for related applications, the following

methods have not been used to characterise silicone on hair, but seem very promising :l XRF (only used to characterise silicon in bulk hair analysis and silicone polymer on skin and

paper).l Pyrolysis (only used as a preparation prior to XRF analysis of trace element in hair bulk

analysis and as part of GC/MS analysis of PVP on hair).

l Wettability measurements (used to qualitatively characterise the surface of hair fibres

treated with conditioning agents and surfactants; only Watanabe and Yahagi (1995) applied

them very recently to characterise pure silicone on hair).

The potential use of these methods to characterise low levels of silicone deposited on hair by 2-

in-1 shampoos is explored in the following paragraphs.

A New XRF Method for Bulk Analysis of Silicone on Hair

Sample pre-treatment and preparationTresses of virgin brown hair from Hugo Royer in tresses of 2.5 g and 20 cm were washed three

times with a 30% sodium lauryl sulfate solution (Empicol LX28) and successively dipped during

30 sec into chloroform, 30 sec in methanol, and 30 sec in chloroform.

Prior to the XRF analysis, the hair samples were pyrolysed (isothermal run at 200C during 2

hours in an oven, followed by a dynamic run up to 700C during 1 h 30 min in a furnace).

Temperature and duration of both pyrolysis steps were optimised via thermogravimetric studies.

The resulting ashes were compressed into a 16 mm pellet and incorporated on top of a 40 mm

pellet made of H3BO 3. Both pellets were compressed under 40 tons, using an Autopress T40 from

Graseby Specac.

For this study, ten samples at a time were pre-treated and prepared.

XRF equipment and procedureThe XRF apparatus is a sequential wavelength-dispersive X-ray spectrometer Siemens SRS 3000. It

includes a Rh X-ray tube, a 100 position sample turntable, and a flow counter detector. The

analytical conditions included a PET (Pentaerythrite) analyser crystal and a scanning rate of 2

min/degree. The peak is the Si Kalphal ray, measured at 109.2C. Backgrounds are measured at

107.3 and 110.8C.

The data were gathered and treated using Siemens Spectra 3000 software. The neat peak

intensity was considered as directly proportional to the concentration (i.e., no correction was

made) because the hair matrix is made of non-absorbing light elements and the thickness of the

hair ashes is much smaller than 1 mm (Eberhardt, 1989).

Determining the Si content of ten samples takes about 30 minutes.

Validation of the proposed methodValidation of this method is based on the following requirements:

l During the pyrolysis step, the silicone film deposited on the hair is fully thermally degraded

into silica ash.

l The XRF method analyses silicone and not specifically silicone polymer. The amount of Si

within the hair shaft must be low compared to the amount of silicone deposited on the hair

surface; moreover, the Si content of the hair shaft must be homogeneous within a single

hair lot.

Thermal degradation of the silicone film

Following Lipowitz and Ziemelis (1976) and Larena et al. (1992), silicone species of more than

5 cS undergo a surface oxidation during burning into a white surface silica ash with a gelled

methylsiloxane layer beneath. Subsequently, all silicone will be oxidised into silica, provided


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enough oxygen is available during the pyrolysis and the silicone layer present on hair is thin

enough.

Si present within the hair shaft

Although 40 trace elements have been measured in hair, not a lot of data exist concerning Si level.

Wilkinson and Moore (1982, p.410) give a value of 188 ppm for European brown hair.

In order to check the robustness and representativity of this analysis, the level of other trace

elements more commonly reported in the literature, like Fe, Cu, Zn and Pb, has been comparedin Table 3. Considerable variation is observed. Fe and Cu concentrations range between a few

ppm and about 200 ppm. This would suggest that the Si content of hair may also be very variable

and even as low as a few ppm.

XRF analysis of Si carried out in this study on several hair tresses of the same lot has shown a

standard deviation of 10% between the different hair tresses and a Si average value 3 to 5 times

lower than the one found for hair tresses washed with conditioning shampoos containing silicones

(depending on the shampoo formulation).

Table 3. Comparison between Fe, Cu, Zn, and Pb levels (in ppm) in hair.

References

Wilkinson and Moore, 1982

Havranek et al., 1989

Iengar et al., 1978

Sturaro et al., 1993

Torok et al., 1984

Total range

Fe Cu

133 64

50-88 4-134

5-45 11-34

- 11-22

65 38

5-133 4-134

Zn Pb

116 21

169-220 10-12

99-450 3-70

189-319 5-9

228 9.5

99-450 3-70

Linearity, calibration, and cross correlation with AA

Standards were prepared by dipping several of these tresses into a solution of various amounts of

high molecular weight dimethicone diluted in cyclomethicones (Dow Corning 345 Fluid and 1401

Fluid). These standards have been analysed by AA following the procedure described in Klimisch

(1991), and by XRF following the method described hereabove. The Si detection results obtainedby the two methods correlated very well. The XRF calibration curve is linear down to 5 ppm.

Wettability Measurements

Sample pre-treatment and preparation

Virgin brown hair from Hugo Royer in tresses of 2.5 g and 20 cm were washed three times with a

30% sodium lauryl sulfate solution (Empicol) and successively dipped during 30 sec into

chloroform, methanol, chloroform.

Because the hair hydrophilicity increases as a function of its distance to the root, hair samples

of 5 mm long were cut at the middle of the tress. Their diameter is measured using a Zeiss optical

microscope.

Equipment and procedureWettability measurements were carried out using a Kruss El4 tensiometer. The method consists of

hanging a 5 mm hair sample on a scale and dipping it into water. The wettability of hair fibre is

measured by the instrument as being the difference between its weight in air and its weight at the

contact with water. For each hair tress, thirty samples were analysed, and their wettability values

averaged.

Validation of the proposed methodThree sets of samples were analysed for their wettability in pure water : (1) untreated hair, (2)

silicone-coated hair, and (3) hair washed with shampoos containing silicone. The results show that

the three samples were significantly different from one another at more than 99% confidence.

Untreated hair was less hydrophobic and silicone-coated hair was more hydrophobic.


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A. De Smedt et al.

This method is qualitative; it is sensitive to the presence of silicone on hair, not to the level of

silicone. For example, hair coated with 700 ppm silicone has given exactly the same wettability

value as hair coated with 100 ppm.

ConclusionsThis paper outlines two innovative methods to analyse and characterise low levels of silicone

deposited on hair by 2-in-1 shampoos.l The bulk hair analytical method consists of a pyrolysis step followed by XRF Si detection. Its

main advantages are speed, low detection limit, and accuracy. It seems to be a very

promising screening tool, which could act as a back-up for AA tests.

l The single hair fibre surface analytical method consists of single fibre wettability

measurements. It provides information on the change in hydrophilicity of the shampooed

or silicone-coated hair. The method, still at an initial development stage, is sensitive to the

presence of silicone and not to its concentration level.

AcknowledgementThe authors wish to thank Anne Dupont and Brenda Reimer for their contribution.

ReferencesAlexander. Ph., 1992, Manufacturing Chemist, Feb. 1992; 28-32.

Bergman, W., and Bees, J., 1991, Patent EP 0 455 185 A2.

Berthiaume, M.D., Merrifield, J.H., and Riccio, D.A., 1995, J. Soc. Cosmet. Chem., 46, 231-245.

Berthiaume, M.D., Riccio, D.A., Merrifield, J.H., 1994, DCI, Dec. 1994, 24-32.

Bogardus, R.E., Packer, J.D. and Sanogeira, J.P., 1985, US Patent 4, 515, 784, May 7, 1985 (assigned

to Richardson-Vicks Inc).

Bottoms, E., Wyatt, E., and Comaish, 1972, Brit. J. Derm., 86, 4, 379-384.

Braida, D., Dubief, C., Hallegot, P., and Lang, G., 1994, 18th IFSCC Congress, Venezia, Italy,

Platform Presentations Preprints, 3, 801-817.

Cipriani, C., Aragno, I., Odetti, P., and Rolandi, R., 1994, 18th IFSCC Congress, Venezia, Italy,

Posters Preprints, 737-752.

Cortes-Toro, E., De Goeij, J.J.M., Basco, J., Cheng, Y-D., Kinova, L., Matsutara, J., Niese, S., Sato, T.,

Wesenberg,G.R., Muramatsu, Y., and Parr, R.M., 1993, J. Radioanal. Nucl. Chem., 167, 2, 413-421.

Eberhart, J.P., 1989, Analyse structurale and chimique des materiaux, Dunod eds., 614 pp.

Eltayeb, M.A.H., and Van Grieken, R.E., 1989, J. Radioanal. Nucl. Chem., 131, 2, 331-342.

Folin, M., Contiero, E., and Calliari, I., 1991, Ann. Chim. (Rome), 81, 1-2, 39-49.

Goddard, E.D., and Harris, W.C., 1987, J. Soc. Cosmet.Chem., 38, 233-246.

Goddard, E.D., and Schadt, R.L., 1988, 15th IFSCC Congress, London, UK, Paper Preprints, 2,

197-209.

Grooch, E., and Kohl, G., 1988, J. Soc. Cosmet. Chem., 39, 383.

Havranek, E., Bumbalova, A., and Harangozo, M., 1989, J. Radioanal. Nucl. Chem., 135, 5, 321-331.

Helliwell, J.F., 1994, Patent WO 94/03152 (Unilever).

Holt, L.A., 1991, J. Soc. Cosmet. Chem., 42, 351-359.

Horner, H.J., Weiler, J.E., and Angelotti, N.C., 1960, Anal. Chem., 32, 7, 858-861.Iyengar, G.V., Kollmer, W.E., and Bowen, H.J.M., 1978, Elemental Composition of Human Tissues and

Body Fluids, Verlag Chemie ed., Weinheim.

Joy, M., and Lewis, D.M., 1991, Int. J. Cosmet. Sci., 13, 249-261.

Jurdana, L.E., Ghiggino, K.P., Leaver, I.H. and Baraclough, C.G., and Cole-Clarke, P., 1994, Appl..

Spectrosc., 48, 44-49.

Kamath,Y.K., Dansizer, C.J., and Weigmann, H.-D., 1984, J. Coll. Int. Sci., 102, 1, 164-172.

Kamath, Y.K, Dansizer, C.J., and Weigmann, H.-D., 1984, J. Appl. Polym. Sci., 29, 1011-1026.

Kamath, Y.K, Dansizer, C.J., and Weigmann, H.-D., 1985, J. Appl. Polym. Sci., 30, 925-936.

Kamath, Y.K., Dansizer, C.J., and Weigmann, H.-D., 1985, J. Appl. Polym. SCi., 30, 937-953.

Kamath,Y.K, Dansizer, C.J., Hornby, S., and Weigmann, 1987, Textile Res. J., April 87, 205-213.

Kanetake, S., Tomizawa, K., Tyo, H., and Nakamura, Y., 1992, 17th IFSCC Congress, Yokohama,

Japan, Paper Preprints, 1059-1071.


9/10


Klimisch, H.M., Kohl, G.S., and Sabourin, J.M., 1987, J. Soc. Cosmet. Chem., 38, 247-262.

Klimisch, H.M., and Chandra, G., 1986, J. Soc. Cosmet. Chem., 37, 73-87.

Klimisch, H.M., 1991, in The Analytical Chemistry of Silicones, ed. A.E. Smith, 112; J. Wiley and Sons,

117-132.

Larena, A., Matias, M.C., and Martinez Urreaga, J., 1992, Spectrosc. Lett., 25, 7, 1121-1129.

Lipowitz, and Ziemelis, M., 1976, J. Fire and Flammability, 7, 504-529.

Pavlichko, J., Goddard, E.D., and Schmidt, R.L., 1994, 18th IFSCC Congress, Venezia, Italy, PaperPreprints, 1, 98-104.

Qi, W., Furutani, K., and Awashi, Y., 1986, Guangpuxue Yu Guang pu Fenxi, 6, 2, 53-55.

Robbins, C.R., and Bahl, M.K., 1984, J. Soc. Cosmet. Chem., 35, 379-80.

Schmitt, R.L., and Goddard, E.D., 1994, Cosmetics and Toiletries, 109, 3, 83-93.

Sejpka, J., 1993, SPC, April 1993, 29-31.

Smarajit, M., 1995, Cosmet. Toil. Manuf. Worldw., 177-179.

Solka, B.H., and Kocis, J.A., 1994, 18th IFSCC Congres, Venezia, Italy, Paper Preprints, 385-401.

Sturaro, A., Parlovi, G., Doretti, L., Zanchetta, S., Allegri, G., and Battiston, G., 1993, Anal. Chim.

Acta, 274, 163-170.

Starch, M.S., 1984, DrugCosmet. Ind., 134, 6, 38.

Swift, J.A., 1991, Int. J. Cosmet. SCi., 13, 3, 143-159.

Todd, C.H. and Hayes, S., 1971, Am. Perf. Cosmet., 86, 10, 112.

Torok, S., Van Dyck, P., and Van Grieken, R., 1984, X-Ray Spectrum., 13, 1, 27-32.Volkov, V.F., Arzhanov, I.G. and Semenova, E.V., 1994, Zavod. Lab., 60, 12, 23-25.

Watanabe, S. and Yahagi, K., 1995, J. S.C.C.Japan, 29, 1, 64-68.

Wendel, S.R. and Disapio, A.J., 1983, Cosmet. Toilet., 98, 5, 103.

Wilkinson, J. B. and Moore, R. J., 1982, Chemical publishing, New York, 935 pp.

Wu, X.K., Zeng, X.Z.andYao, H.Y., 1993, Nucl. Instrum. Meth. Phys. Res., Sect. B, B75, 567-570.

Yahagi, K., 1992, J. Soc. Cosmet. Chem., 43, 275-284.


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measurement of silisone deposition by various analytical method

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