ANALYSIS OF SHAMPOOS 895 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 poly- amine-type of ion exchange resin (Amberlite IR-45), previously washed with 1N NaOH solution followed by thorough back-washing with dis- tilled 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 non- ionic surfactants in the sample, one should start with a fresh sample (with- out 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 ex- change 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-

896 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 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 øC, and saturated at this tem- perature 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)