364 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I. Interaction of dental cream components Absorbance Material I 2 3 Chlorhexidine 1.250 1.198 1.235 Chlorhexidine + Monofluorophosphate 1.295 1.260 1.277 Natrosol 1.253 1.262 1.285 Benzocain 1.245 1.205 1.260 Methofas 1.188 1.272 1.255 Miranol 1.213 1.265 1.300 Cyclamate 1.262 1.235 1.258 Sodium fluoride 1.271 1.255 1.280 Flavour (typical) 1.166 1.225 1.262 Glycerol 1.234 1.182 1.288 Colour (typical) 1.247 1.200 1.280 Alumina (Gibbsite) 1.230 1.180 1.256 Table II. Recovery of chlorhexidine from a dental cream % Chlorhexidine % Chlorhexidine % added found Recovery 0.395 0.391 99.0 0.400 0.402 100.5 0.493 0.513 104.1 0.499 0.511 102.4 0.594 0.596 100.3 0.594 0.606 102.0 Table III. Typical analyses of freshly-prepared chlorhexidine dental creams % Chlorhexidine Cream No. Formulated Found Mean Recovery 1 0.62 0.61 0.62 0.63 0.62 100 2 0.50 0.50 0.49 0.49 0.49 98 3 0.50 0.50 0.51 0.50 0.50 100 4 0.50 0.51 0.52 0.52 0.52 104 5 0.50 0.50 0.50 0.51 0.50 100 6 0.50 0.50 0.50 0.50 0.50 100 7 0.50 0.49 0.48 0.49 0.49 98 8 0.50 0.48 0.47 0.49 0.48 96 9 0.50 0.51 0.50 0.51 0.51 102 to a typical blank dental cream. The results quoted in Table H show that the recoveries of chlorhexidine were excellent the mean being 101.4•o. A series of freshly-prepared dental creams were analysed for chlor- hexidine using the proposed method. The results obtained, comparing the

DETERMINATION OF CHLORHEXIDINE IN ORAL PRODUCTS 365 formulated level and the analytical values are recorded in Table III. These results show again that recovery is excellent, in this case the mean being just below 100•. Replicate analyses carried out on a cream formulated to contain 0.5• of chlorhexidine base showed that the standard deviation was 5r0.022 at this level. Determination of'total chlorhexidine' Using the procedure described, a linear calibration curve was obtained up to 300 [tg of p-chloroaniline. Table IV. Recovery of chlorhexidine and p-chloro aniline from an alumina based dental cream (a) Chlorhexidine gluconate added % Added % Found % Recovery 0.265 0.252 95.0 0.245 0.243 99.1 0.500 0.471 94.1 0.516 0.497 96.3 1.013 1.007 99.4 1.006 0.987 98.1 . 97.0 (b) Chlorhexidine diacetate added % Added % Found % Recovery 0.238 0.225 94.5 0.236 0.237 100.4 0.465 0.456 98.1 0.470 0.460 97.9 0.719 0.701 97.5 0.723 0.696 96.3 (c) p-Chloraniline added [tg Added gg Found % Recovery 50.1 54.3 108.4 50.1 53.0 105.8 100.2 97.8 97.6 100.2 97.8 97.6 150.3 148.4 98.7 150.3 149.0 99.1 Table IVrecords the results obtained when using the described procedure to determine the recovery of chlorhexidine and p-chloroaniline from a dental cream formulated with an alumina as abrasive. The chlorhexidine was added as (a) the gluconate, and (b) the diacetate and the p-chloroaniline