THE SORPTION OF AMINO ACIDS FROM SHAMPOOS ON TO HAIR 273 extraction with 6N HC1 and repeated extraction with water. Up to 70 per cent of the deposited amino acid was found to be removed by the shampoo. An increase in the amount of amino acid in the shampoo led to an increase in the amount sorbed by the hair. Experiments of the same type using •4C tyrosine gave similar results but indicated that slight variations in the washing and rinsing techniques resulted in large variations in the absolute amount of the amino acid sorbed, thereby necessitating the use of internal controls. The human hair used in the experiments, having been washed in a mild soapless shampoo, was specially selected and blended in order to lessen hair variation between experiments. In the washing procedure used, a 12 g tress of hair was pre-wetted in 200 ml tap water at 35 ø C and washed in 200 ml of a standard shampoo solution, based on commercial lauryl sulphate at 35 ø C for 3 minutes, by continual total immersion followed by pulling between the forefinger and thumb to squeeze out excess solution. Rinsing was carried out three times in 200 ml tap water at 35 ø C for 1 minute each time, in the same manner as in the washing. In this process, about 11 ml of solution was carried over from each of the rinses, in a 12 g tress of hair, as calculated from the activity of the rinsing solutions. The activity of the final rinse was negligibly small compared with the activity remaining on the hair. After rinsing, the hair was blotted to remove excess water leaving about 5 ml water in a 12 g tress of hair, after which the hair was allowed to dry at room temperature. In the elution procedure, a weighed sample of hair (approx. 1 g) was gently stirred with 20 ml conc. HC1 for 15 minutes, the acid eluate trans- ferred by pipette into a Craig rotary evaporator and evaporated to dryness under reduced pressure at about 40 ø C. The extraction of the hair was' con- tinued with alternate 20 mi. portions of 6N HC1 and conc. HC1, each extract being combined and evaporated in the same flask. The use of alternate portions of conc. HC1 was found useful in that the hair was more limp and more easily handled than if 6N HC1 was used throughout. It was found in later experiments with tyrosine that 10 such extractions were necessary, so that in practice 12 extractions were given, followed by 4 more, these being evaporated separately in another flask. This latter could then be checked to ensure complete elution of the labelled amino acid. HC1 was removed from the extract by repeated evaporation with water, the dry residue taken up in 1.5 ml hot distilled water and transferred by pipette to a weighed counting planchet where the solution was dried by an infra-red lamp. The transfer was made quantitative by performing three such operations, rinsing the flask thoroughly in the process. The dried material was weighed and counted in a Labgear perspex castle, 0.15" from the window of a Mullard MX 123 Geiger Muller tube, operating at 700 volts. The material

274 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS extracted was very hygroscopic and it was necessary to surround the planchet with silica gel to prevent moisture absorption during the counting period. A self absorption curve was determined using 0.05t• curie and 0.005t• curie •4C tyrosine with varying amounts of tyrosine hydrochloride, plated and counted under the same conditions. A straight line was obtained when log activity was plotted against weight taken, over the range 10 to 70 mg. The weight of material eluted from about 1 g hair was usually in the region of 20-30 mg, consequently it was considered that the counts could be corrected, by means of the self absorption curve, to a constant weight of 20 mg for comparison. The counts were corrected further by equating to unit weight of hair. Two methods of establishing controls were considered: (1) The major tress would be cut in pieces of fixed length, some of which could be used as controls, and (2) the maior tress would be divided into sub-tresses, two or three of which could be used as controls. This latter method was the one used in the preliminary experiments. In the first method a tress of hair 12" in length and 12 g in weight was used and in which the individual hairs were of equal length. It was tied 1_,, from the root end, the other end being accurately clubbed. After washing in 200 ml shampoo containing •4C tyrosine (32/• curies) the tress was cut into 1 in. lengths from the clubbed end, and the lengths weighed. The pieces of hair were extracted and the eluted materials counted and corrected as described (Table 1). Table 1 5ORPTION OF 14C TRYOSINE ALONG THE LENGTH OF A TRESS A 12 g 12" length tress of hair washed in 200 ml shampoo containing 32ix curies •4C tyrosine. 1" lengths were cut and •4C tyrosine eluted and counted. Activity was corrected to constant weight of eluate and unit weight of hair. Activity (counts/ Inches from root end min./g (hair 1 2 3 4 5 6 7 8 9 10 Tress 1 1,613 1,136 1,052 1,015 999 1,047 1,083 1,110 1,200 957 Tress 2 1,249 -- 881 832 825 863 820 735 759 824 It is apparent from the results obtained (1) that the sorption is not uniform along the length of the hair, the results tending to lie on a parabola, and (2) that the sorption is not consistent from tress to tress. The high results obtained from the first two inches is obviously an end effect, the irregularities at the tied end could be due to irregularities in the washing technique enhanced by the bunching of the hairs. It was obvious that this method could