JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (c) Introduce about 1 ml cyclohexane (internal standard) into the small aerosol bottle by means of a plastic disposable syringe (without needle), and plastic transfer pieces (3 and 5). Weigh accurately and find the weight of the internal standard. No phase separation should occur in the liquid mixture. If so, too much cyclohexane has been added. Sampling should be repeated with less cyclohexane. The Pressure-Lok A2 syringe can now be filled with the pressurized liquid mixture in the small glass aerosol bottle. Disconnect the needle of the syringe. Push with the thumb the syringe valve to position 'open'. Slowly move up and downwards the piston several times, taking care that it reaches the syringe bottom completely each time. This is an extremely important operation, which should be carefully done, in order to take a representative sample of the mixture. No gas space should be present in the syringe. Close the syringe valve with the thumb at approx. 20 I. tl. Control for leaks by waiting a minute and holding the syringe piston in a fixed position. No 'gas' space should appear in the syringe. Injection into the gas chromatograph can now be done. Put the needle on the syringe, inject into the septum. Push the valve on 'open' and immediately push down the piston. (Facing p. 201)

RISK-BEARING SUBSTANCES IN COSMETICS 201 of the standard peak J mixture (% by weight) • areas j •9'•2% 116 385270 Propel lant 12 16.97% 308 164351 Propel lant II 6.67% 483 121485 Acetone 1.71% o 745 34789 Methanol 13.19% 848 180125 Dichloromethane 6,69% 1095 100240 CYCLOHEXANE 3.33% 1222 64271 Ethanol 6.85% c,• 1363 653•4 Methylchloroform 3.31% o 1528 56729 isoPropanol 1.96% I 1752 29130 Nitrometha IOO.OO% o Figure 12. Example of the determination of correction factors F. 20 pl of a standard mixture of known composition are injected. The correction factors F are calculated by the formula: Fx xx As in which Fx is the correction factor of compound 1 xx is the weight per cent of compound 1 in the mixture s is the weight per cent of internal standard in the mixture (Cyclohexane) Ax is the integrated peak area of compound 1 A s is the integrated peak area of the internal standard cyclohexane. The calculated correction factors are: Propellant 12 = 1.53 Methanol = 0.74 Methylchloroform = 1.57 Propellant 11 = 1.55 Dichloromethane = 1.10 isoPropanol = 0.87 Acetone = 0.82 Ethanol = 0.78 Nitromethane -- 1.01