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J. Soc. Cosmet. Chem., 23, 887-898 (December 6, 1972)

Methods Used in the Analysis of Shampoos

R. F. SCHUBERT, B.S., and P. H. KO, B.S.*

Presented October 11, 1971, Joint Symposium of the Society of Cosmetic Chemists and the Association of Ocial Analytical Chemists, Washington, D.C.

Synopsis--Modern SHAMPOOS are designed not only to clean the hair and scalp, but to impart conditioning properties, fragrance, luster, and other attributes to hair. As a consequence, the ANALYSIS of a shampoo becomes a complicated exercise in separation and identification of components, calling on many of the disciplines of modern analytical chemistry.

The literature on shampoo analysis is reviewed and some older schemes of analysis are discussed. A proposed scheme for the analysis of a modern shampoo using a combination of SOLVENT EXTRACTION and ION EXCHANGE SEPARATION is presented.

INTRODUCTION

Schwartz and Perry (1) and others state that the main requisites of a shampoo are: (a) it must clean the hair and scalp; (b) it must leave the hair lustrous; (c) it must leave the hair soft rather than harsh and dry (i.e., it must provide conditioning); (d) it must rinse off easily and com- pletely enough not to interfere with subsequent treatment; (e) it must not be irritating; and (f) it must be esthetically pleasing in odor, physical form, visual impact, etc. To achieve these properties, many popular brands of shampoos are based on mixtures of synthetic detergents or synthetic detergents and soap (2, 3). Soap in such mixtures is generally not present as a detergent, but rather as a conditioner.

The physical forms of shampoos found in the market place include clear liquids, liquid creams (or lotions), pastes, gels, aerosols, and powders

* The Gillette Company, Personal Care Division, Merchandise Mart, Chicago, Ill. 60654.

887

888 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS

(2). It is obvious that the formulations needed to achieve the product requisites and physical forms are an analytical chemist's nightmare when he tries to analyze them.

SURVEY OF SHAMPOO ANALYSIS METHODS

Shampoos have been identified by a number of workers as examples of complex mixtures of surfactants which present difficult problems for analysis (4-6). Various methods are used by these workers to classify surfactants, including functional group analysis (7), elemental analysis (6), and paper chromatographic separation and identification (6, 8). All methods used are qualitative or semiquantitative, at best.

Specific references to the analysis of shampoos are not plentiful in the literature. The earliest dated reference in the chemical literature is by Rosenberger (9) who published qualitative and quantitative methods for determining soap and inorganic salts in shampoo powders in 1938. In 1942, Ram (10) reported the analysis of an alkali sulfate and an alkyl sulfate or sulfonated oil in the presence of each other in another shampoo powder. Ram's work is the first reported analysis of a synthetic detergent in a shampoo.

In 1949, Parisot (11) described an analytical scheme applicable to liquid shampoos. From a single sample, he separated by solvent extraction the free fatty acids, fatty acids combined in soap, fatty acids in unsaponified material, the unsaponified material itself, and sulfonated detergent. Other components were determined on separate samples.

In 1958, Newburger (12) described the analysis of shampoos using ion exchange resin. Figure 1 shows an abbreviated scheme of analysis. Note that the method is applicable to shampoos containing an alkyl sulfate, a fatty acid-alkanolamine condensate, and soap. This method is still useful for shampoos with these components. Bush (13) cited the Newburger paper in his review of analysis in the cosmetic industry in 1959. He indi- cated the potential error in attempting to determine an alkyl sulfate by hydrolysis if a fatty alkanolamide is present and suggested that the determination of an ester value of the separated fats after hydrolysis is a reliable indication of the presence of a fatty alkanolamide. Since alkanolamides are not easily extracted from shampoos by ordinary methods, Bush suggested the use of ion exchange techniques.

Neu (14) and Mapstone (15) contributed methods for determining the foaming properties of shampoos and improving the AOAC water determination (16), respectively. Others dealt with problems of viscosity determination (17) and phosphoric acid emulsifiers in egg shampoos (18).

ANALYSIS OF SHAMPOOS 889

Sample n Acidified Alcohol

I Acidified Alcohol Weakly Basic Ion Exchange Column

Alcohol Eluate I Amm.(NH412CO 3 Eluate I

[ Evap.-Dissolve I NH 4 Alkyl Sulfate lin Water r: Na2C031 /Evap.-Ext. Acer. I

Sap-Na2C03 Residue I Extract

Hot H20-Acid I Fatty Acid-Alkanol Ext. CHCI 3 Amine Condensate Fatty Acids

Simplified schematic of Newburger's shampoo analysis scheme (12)

Newburger was the first to use infrared spectroscopy in shampoo analysis (19). The spectrum of the nonvolatile residue was examined for the possible presence of soap, alkyl sulfates, alkanolamines, fatty acid-alkanolamine condensates, polyoxyethylene compounds, polyhydroxy compounds, and quaternary ammonium compounds. Other qualitative tests were used and water was determined by the AOAC method (16). Separa- tion of the surfactants was by the ion exchange method (12) and is shown in Fig. 1. The separated fractions were examined by ir and identified by their spectra. Although the procedure outlined is quite comprehensive and makes very good use of technology available, it cannot separate and identify alkanolamines which are popularly used in many modern shampoos.

Puttham (20, 21) applied another ir technique to qualitative and quantitative analysis of surfactants in shampoos. He used a Teflon * seal with a backing plate on the back face of a KRS-5 attenuated total reflectance (ATR) prism forming a cell to contain a liquid shampoo which can be scanned by ir. Spectra obtained over the "fingerprint region" were used to identify an ethoxylated alcohol, a sulfated alcohol, and a sulfated fatty alcohol ethoxylate. The qualitative method was adapted to a quantitative method for lauryl ether sulfate by measuring the sulfate absorbance

* E. I. dupont de Nemours Corporation, Wilmington, Del.


at 1220 cm -. Excellent correlation of the method with the cationic titra-

tion method was claimed over the range of 16-19%. It was reported that the method could also be used to determine sodium and triethanolamine

salts of sulfated fatty alcohols. Schwarz (22) stated that the analyst must have some idea of the com-

ponents to determine how to proceed with the shampoo analysis. He made use of the titrations of Epton (23) and Barr et al. (24) before and after acid hydrolysis, and the hydroxyl number of the fatty alcohol or the acid number of the fatty acid thus liberated. He advised the use of gas chromatography to determine carbon-chain distribution of the acid or alcohol. He also discussed the practicality of column chromatography, solvent extraction, thin-layer and paper chromatography. An ir spectrum might be useful if the mixture is not too complex. A very serious problem to analysis of shampoos, he pointed out, is that the raw materials used in the surfactants are not lure. Schwarz stated that, in the analysis of shampoos, a compromise must be made between the cost and the expenditure of time and the desired results. It was Schwarz' opinion that often the results obtained are not worth the expenditure (22).

Thin-layer chromatography (tlc) has been used for the separation of ionic and nonionic surfactants, free fatty alcohols, and free amines in shampoos (25). Other workers (26, 27) have used tlc for separating zinc lyrithione from other shampoo ingredients.

Gas chromatography has been used to determine triethanolamine lauryl sulfate (28) and free propylene glycol in shampoos (29).

Fairchild (30) suggested a shampoo separation scheme in 1967. The sample was dissolved in water and extracted with petroleum ether. When the water in the aqueous fraction was reduced to a small amount, the cellu- lose precipitated out and could be removed from triethanolamine lauryl sulfate. The two fractions were then dried and determined quantitatively. The methylene blue test of Jones (31) was used to confirm the alkyl sulfate. Other identifications were made by ir spectroscopy. The petroleum ether-soluble components were separated on an alumina column with increasingly polar solvents. Infrared was used to identify the material eluted. The nonionic surfactants were eluted with some of the super- amide and soap in the ethanol fraction. Because of this, the scheme is not as complete as one would like, but it goes a long way toward solving some of the problems previously encountered. There is also some question about the completeness of the separations between some of the fractions.

Perfumes in shampoos have been determined qualitatively and quantitatively by uv spectrophotometry (32).


From the foregoing, one might conclude that there is no single univer- sal method which can be used to analyze all kinds of shampoos. A more rewarding approach, in our opinion, would be to use a combination of extraction and column chromatographic techniques to separate the ingredients, without changing their chemical properties, and identifying the separated ingredients with some physical or chemical methods. Infrared spectroscopy appears to be the quickest tool for identification in most of the cases.

PROPOSED METHOD OF SHAMPOO ANALYSIS

The suggested procedure given below is one approach which might be taken to determine the composition of a shampoo:

General Information by Examination of the Infrared Spectra of Solids

A thin film of a partially dried sample (previously heated in a vacuum oven at 70 C for 4 hours) is deposited on a (disposable) silver chloride optical window and the ir spectrum is recorded. Then, the ir spectrum of a water-free sample deposited as a thin film on a salt plate is recorded. Figure 2 is a representative spectrum of the water-free nonvolatiles from a commercial shampoo. The presence of polyols and many types of surfactants can be recognized from the ir spectra of the sample.

.oo 0o0 2500 2000 1800 1600 1400 1:200 1000 800 600 FREQUENCY (CM -I)

Figure 2. Infrared spectrum of water-free nonvolatiles of a commercial shampoo (thin film on KBr plate)

Quantitative Estimation of Total Soap and Anionic Sulfated (or Sulf onated) Surf actants

The soap and artionic surfactants present are determined at an early stage of analysis to decide what further procedures to use. Absence of either soap or artionic surfactants may simplify the analysis by permitting


omission of some steps. The well-known cationic-anionic two-phase titration, also known as the Epton-Barr titration (23, 24) method, is one way to do this.

Separation of Cellulosic Materials Many shampoos contain cellulosic materials as thickening agents.

Newburger (19) suggested using ethanol to precipitate water-soluble gums and then preparing a dried film on which the ir spectrum is run with the aid of water-repellent glass plates.

The present authors found that in many cases some water must be removed from the sample in order to precipitate the cellulosic materials with ethanol. The coagulated cellulosic material can be removed by filtering through glass wool and purified by washing with fresh ethanol. To pre- pare the cellulosic material for recording its ir spectrum, it is preferable to make a viscous solution of it with water, deposit a thin film on a silver chloride optical window, and dry in a 105 C oven.

Separation of Alkanolamide from a Shampoo Containing lPropylene Glycol, Soap, and a Sulfated Detergent

It was found that an alkanolamide can be isolated from a shampoo containing propylene glycol, soap, and a sulfated detergent by passing a solution of it through a cationic-anionic mixed bed ion exchange column such as Amberlite* MB-I. Propylene glycol is retained along with the ionic materials. Alkanolamide is recovered by passing ethanol through the column.

In practice, a 2.4-cm i.d. glass column is packed with 50 ml of Amber- lite MB-I resin, 20-50 mesh, and is back-flushed with distilled water to obtain a good packing. A 2-g sample (preferably containing less than 2 meq of total anionic surfactant and soap) is dissolved in about 20 ml of water and passed through the column at 2 ml/min. After the column is rinsed with water (it was noted that very little alkanolamide was eluted with water alone), 200 ml of ethanol is passed through the column at about 4 ml/min, collecting all the effluent. After back-flushing of the resin in the column with just enough ethanol to get rid of the bubbles (without overflowing the ethanol), another 200 ml of ethanol is passed through the column, collected, and combined with the first effluent. To recover the alkanolamide, solvent is evaporated off. Figure 3 is the ir spectrum of an alkanolamide recovered by this procedure.

* Rohm and Haas Go., Philadelphia, Pa.


3500 3000 2500 2000 1800 1600 1400 1200 1000 80C 600 FREQUENCY (CM 4)

Figure 3. Alkanolamide recovered from Amberlite MB-1 ion exchange column (dried residue on KBr plate)

Separation of Soap, Artionic Surfactant, and Nonionic Surfactant in a Shampoo Figure 4 is a schematic representation of the following procedure:

Separation of Soap In the analysis of a shampoo containing soap, artionic surfactant, and

nonionic surfactant, soap is separated by drying the sample with excess sodium carbonate, and extracting the artionic and nonionic surfactants with a mixed solvent of 1: 1 diethyl ether and acetone.

About 5 g of the shampoo sample is thoroughly mixed with an equal weight of pulverized, anhydrous Na2COa and the mixture is dried in a 105 C oven until no further loss of weight. The sample is cooled and extracted with six 20-ml portions of 1: 1 diethyl ether-acetone mixture and the extract is filtered. The flitrates are combined and evaporated to dryness on a steam bath. This extract is reserved for the determination of detergent and nonionic surfactants. A spectrum of this residue from the analysis of a commercial shampoo is shown in Fig. 5.

The soap residue is dissolved in 50 ml of water and acidified with HC1. The fatty acid is extracted with 3 X 30 ml of chloroform and the solvent is evaporated off to recover the fatty acid. Most of the fatty acids recovered can be identified by comparing the gas chromatographic retention times of their methyl esters with that of known methyl esters.

Separation of Artionic Surf actants and Nonionic Surf actants After isolation from soap, the artionic and nonionic surfactants can be

further separated by a two-column ion exchange procedure modified from that of Ginn and Church (33). The artionic surfactant is converted from its sodium form to the hydrogen form by passing a solution of it through a sulfonic acid-type of ion exchanger, and is retained on a polyamine-type


Figure 4.

I Dried Sample I n Na2CO 3 Ext. EtOEt-Acet. Soap and Residue I Fdtrate Arnoinc and (norgenies Nonlomc I 1 Surfactants

Ext CHCl 3 1,1 IPA-H20

I Fatty Acid I Amberlite IR-120

Stnp wth 2NaOH I In 1:1 IPA-H20 I Amberlite IR-45 Ion Exchange

Effluent I I

I Neut. with H2S041 Nonionic ISat. with Na2CO31 Surfactant ! at 60C. I

IPA Layer- Evap

I

1:1 Ether-Acetone Purification Sodium Salt of

Arnoinc Surfactant (It)

Strip with 2N HCI I

Evap to Dryness

Alkanolamlne HCI (ir)

Schematic representation of the separation of a soap, anionic surfactant, and nonionic surfactants in a shampoo

20OO 1goo 16oo FREQUENCY (CM -I)

143 1200 lo00

Figure 5. Infrared spectrum of a commercial shampoo from which soap has been removed (dried residue on KBr plate)


ion exchanger located below the first column. Nonionic surfactants are recovered in the column effluent. The artionic surfactant retained in the

polyamine column is partially recovered by passing a strong alkali solution through the column. After purification it can be identified, in its sodium salt form, by comparing its ir spectrum with known materials.

In practice, a 2.4-cm i.d. glass column is packed with about 125 ml of sulfonic acid-type ion exchange resin (Amberlite IR-120), previously washed with 1N HC1 followed by thorough back-wash with distilled water. Another 2.4-cm i.d. glass column is packed with about 125 ml of polyamine-type of ion exchange resin (Amberlite IR-45), previously washed with 1N NaOH solution followed by thorough back-washing with distilled water. Both columns are back-flushed with 2 1. of 1:1 isopropanol (IPA)-water mixture before use.

A sample (containing no more than 3 neq of total anionics) is pre- pared in 50 ml of 1: 1 IPA-water solvent and the solution is passed through the sulfonic acid column mounted over the polyamine column and then through the polyamine column at 2 ml/min. Enough solvent should be passed through both columns until all the nonionic surfactant is removed. It usually takes about 600 ml of the solvent to elute all the nonionics. The nonionic surfactant is recovered by evaporating off the solvent and its ir spectrum is obtained. For accurate quantitative determination of nonionic surfactants in the sample, one should start with a fresh sample (without drying with Na.COa and solvent extraction) and carry through the procedure for separation of alkanolamide described above.

Recovery of Alkanolamine from the Cationic Exchanger Alkanolamines, such as triethanolamine, are often used in shampoos.

If an alkanolamine is present, it will be retained on the IR-120 ion exchange column used in the separation of anionic and nonionic surfactants. The column can be stripped of alkanolamine as the alkanolamine. HC1 by passing 200 ml of 2N HC1 through the IR-120 ion exchange column at a rate of 5 ml/min and evaporating the effluent to dryness. A smear of the residue is made on a salt plate to record its ir spectrum. This spectrum is then compared with spectra of known alkanolamine-hydrochlorides. A spectrum of triethanolamine separated by this method is shown in Fig. 6.

Recovery of Anionic Detergent from the Polyamine- Type Ion Exchanger A 300-ml solution of 2% NaOH in 1: 1 IPA-water is passed through the

Amberlite IR-45 ion exchange column at a rate of 3 ml/min. The efflu-


3500 3000 2500 2000 1800 1600 ]4oo 7200 1000 80o GO 4oo FREQUENCY (CM -)

Figure 6. Infrared spectrum of triethanolamine. HC1 recovered from commercial shampoo by ion exchange method (dried residue on KBr plate)

ent is neutralized with H2SO4, heated to 60 C, and saturated at this temperature with anhydrous Na2COa to separate the IPA layer from the water layer. After it is cooled to room temperature, the IPA (top layer) is drawn off and evaporated to dryness. The residue contains the sodium salt of the anionic detergent plus some dissolved inorganic salts. To purify the anionic detergent for recording its ir spectrum, the residue is extracted with a solvent mixture of 1:1 acetone-diethyl ether (34), the extract is filtered, then evaporated to dryness.

Recovery of the anionic detergent by this procedure is not quantitative in the authors' experience. However, the recovered material is pure enough for identification by comparison of its spectrum to known spectra. A sodium alkyl sulfate spectrum separated by this procedure is shown in Fig. 7.

3500 3000 2500 2000 1800 1600 1400 1200 1 0oO 800 600 400 FREQUENCY (CM -I)

Figure 7. Sodium alkyl sulfate recovered from polyamine ion exchange column (dried residue on KBr plate)


SUMMARY

A comprehensive literature survey of methods for the analysis of shampoos has been presented. A proposed scheme of analysis for complex modern shampoos using a combination of solvent extraction, ion exchange separation, and infrared spectroscopy is presented.

(Received February 2, 1972)

REFERENCES

(1) Schwartz, A.M., and Perry, J. W., Surface Active Agents: Their Chemistry and Technology, Vol. I, Interscience Publishers, Inc., New York, 1949, p. 444.

(2) Schwartz, A.M., Perry, J. W., and Berch, Julian, Surface Active Agents and Detergents, Vol. II, Interscience Publishers, Inc., New York, 1958, p. 621.

(3) Behrman, H. T., The Scalp in Health and Disease, The C. V. Mosby Co., St. Louis, Mo., 1952, pp. 125-9.

(4) Schwartz, A.M., Perry, J. W., and Berch, Julian, Ibid., pp. 323, 334 if. (5) Rosen, M. J., and Goldsmith, H. A., Systematic Analysis of Surface Active Agents, Interscience

Publishers, Inc., New York, 1960, p. 238 if. (6) Smith, W. B., The analysis of synthetic detergents, d. Soc. Cosmet. Chem., 14 513-27 (1963). (7) van der Hoeve, J. A., Analysis of textile auxiliary products, J. Soc. Dyers Colour., 70 145-

54 (1954). (8) Drewry, J., Quantitative examination of detergents by paper chromatography, Analyst,

88, 225-31 (1963). (9) Rosenberger, G. A., The rapid analysis of shampoo powders containing soap, Seifensieder-

Ztg., 65, 118-20 (1938); Chem. Abstr., 32, 3649 (3), (1938). (10) Ram, S., Analysis of washing powders containing sulfates and sulfonates, Analyst, 67

162 (1942); Chem. Abstr., 36, 5581 (2), (1942). (11) Parisot, Andre, Rapid industrial analysis of soap and soap-like products, Olearia, 3 13-20

(1949); Chem. Abstr., 44, 2263 (c) (1949). (12) Newburger, S. H., The analysis of shampoos, J. Ass. OjSc. Agr. Chem., 41,664-8 (1958). (13) Bush, S. J., Chemical analysis in the cosmetic industry, J. Soc. Cosmet. Chem., 10 258-71

(1959). (14) Neu, G. E., Techniques of foam measurement, Ibid., 11,390-414 (1960). (15) Mapstone, G. E., The determination of water in shampoos by distillation, Ibid., 12 397-

400 (1961). (16) Sallee, E. M., Ed., OjScial and Tentative Methods of the American Oil Chemists' Society, AOCS,

Chicago, Ill., 1970, Method Fla-44. (17) Oriol Pascual, D. J., Problems encountered in determining the viscosity of shampoos

Parrum. Cosmet. Sayohs, 9, 171-8 (1966); Chem. Abstr., 65, 8662 (h), (1966). (18) Benk, E., and Treiber, H., Identifying phosphoric acid emulsifiers in shampoos containing

egg products, Riechst., Aromen, Koerperpflegem., 16 306-8, 310 (1966); Chem. Abstr., 66 13997 (t), (1967).

(19) Newburger, S. H., A Manual of Cosmetic Analysis, Association of Official Agricultural Chemists, Washington, D.C., 1962, pp. 36-43

(20) Puttnam, N. A., Lee, S., and Baxter, B. H., Application of attenuated total reflectance infrared spectroscopy to toilet articles and household products. I. Qualitative analysis, J. Soc. Cosmet. Chem., 16, 607-15 (1965).


(21)

(22)

(23)

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(25)

(26)

Puttnam, N. A., Baxter, B. H., Lee, S., and Stott, P. L., Application of attenuated total reflectance infrared spectroscopy to toilet articles and household products. II. Quan- titative analysis, Ibid., 177 9-16 (1966 ). Schwarz, G. W. G., Possibilities and limitations of shampoo analysis, Ibid., 17, 737-44 (1966). Epton, S. R., New methods for the rapid titrimetric analysis of sodium alkyl sulfates and related compounds, Trans. Faraday Soc., 44, 226 (1948). Barr, T., Oliver, J., and Stubbings, W. V., The determination of surface active agents in solution, J. Soc. Chem. Ind., 67, 45-8 (1948). Yoshikawa, K., Nishina, T., and Takehana, K., Thin-layer chromatography of detergents. I. Simultaneous analysis of commercial liquid shampoos and liquid dishwashing detergents by TLC, Yukagaku, 15, 65-72 (1966); Chem. Abstr., 64, 11445 (h), (1966). Fairchild, (2. M., and Kabacoff, B. L., Analytical chemistry of zinc pyrithione, VI, presented at semi-annual meeting of the Society of Cosmetic Chemists, New York, May 8, 1969.

(27) Graber, M. B., Domsky, I. I., and Ginn, M. E., Thin-layer chromatographic method for identification of germicides in personal care products, J. Amer. Oil Chem. Soc., 46, 529-31 (1969).

(28) Jones, J. H., Newburger, S. H., Champion, M. H., Kottemann, C. M., and Gross, F. C., Gas chromatography in cosmetic analysis, Proc. Joint Conf. Cosmet. $ci., 75-89 (1968), Toilet Goods Assoc., Washington, D.C.; Chem. Abstr., 70, 109096 (g), (1969).

(29) Gross, F. C., and Jones, J. H., Determination of propylene glycol in cosmetics by gas chromatography, J. Ass. Offc. Anal. Chem., 50, 1284-6 (1967).

(30) Fairchild, C. M., Analytical chemistry in the cosmetics industry, Anal. Chem., $9 (10), 22A-24A, 26A, 28A, 30A, 32A, and 34A (1967).

(31) Jones, J. H., General colorimetric method for determination of small quantities of sulfonated or sulfated surface-active compounds, /. Ass. Offc. Agr. Chem., 28 398-409 (1945 ); Chern. Abstr., $9, 3951 (q), (1945).

(32) Kecskemethy, L., Szamoskozi, Z., Weber, C., and Bozoki, G., Qualitative and quantitative analysis of perfumes by uv spectrophotometry, Olaj, Szappan, Kozmet, 17, 23-6 (1968).

(33) Ginn, M. E., and Church, C. L., New columnar and mixed-bed ion exchange methods for surfactant analysis and purification, Anal. Chem. $1,551-5 (1959).

(34) Ross, L. U., and Blank, E. W., Error in the determination of the active ingredient in detergent products, J. Amer. Oil Chern. Soc., $,}, 70 (1957).

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