SIMULTANEOUS GC ASSAY OF DEG AND EG 227 EXPERIMENTAL INSTRUMENTS AND CONDITIONS Analyses were performed on an Agilent Technologies 5890 gas chromatograph system that included a fl ame ionization detector, a model 7673 autosampler, and ChemStation software (Agilent Technologies, Palo Alto, CA). The column was a 30-m ´ 0.32-mm i.d. HP-5 fused silica capillary column coated with 5% diphenyl–95% dimethylsiloxane co- polymer (crosslinked) at 0.25-mm fi lm thickness (Agilent Technologies #19091J-413). The inlet split liner was an SGE FocusLiner. The column was installed into a split/split- less injection port held at 300°C and connected to a fl ame ionization detector held at 300°C the carrier gas was helium held at 10 psi head pressure with a split ratio of about 30:1. The GC oven temperature was held at 90°C for four minutes, then programmed at a rate of 10.0°C/min. to reach a temperature of 280°C, where it was then held constant for fi ve minutes. With these conditions, the retention times for silylated ethylene glycol, silylated propylene glycol, silylated diethylene glycol, silylated glycerin, and silylated sorbitol were approximately 2.8 minutes, 3.1 minutes, 7.7 minutes, 8.2 minutes, and 17 minutes, respectively. REAGENTS AND SOLUTIONS ACS reagent grade DMF (N,N-dimethylformamide) was obtained from Fisher Scien- tifi c (Pittsburgh, PA). BSTFA reagent (bis[trimethylsilyl]-trifl uoroacetamide containing 1% trimethylchlorosilane) was obtained from Regis Technologies (Morton Grove, IL). Diethylene glycol, ethylene glycol, glycerin, and propylene glycol reference standards were purchased from either USP or Sigma Aldrich (St. Louis, MO). USP sorbitol solu- tion was obtained from ADM (Archer Daniels Midland). Real-world USP-grade glyc- erin samples were produced by Dial Corporation’s bar soap manufacturing facility (Montgomery, IL, now owned by VVF Corporation) PEG-6 methyl ether, PEG-8, and PEG-12 were provided by Lambent, Huntsman, and Dow. To prepare the mixed stan- dard solution, about 0.15 g each of DEG and EG were accurately weighed (± 0.0001 g) into a single 100-ml volumetric fl ask, then mixed and diluted to volume with DMF then 5.00 ml was pipetted into a 50-ml volumetric fl ask and mixed and diluted to volume with DMF. On each day of use, a 250-ml portion from the dilute mixed stan- dard was transferred to an autosampler vial where it was mixed with 500 ml of BSTFA reagent. ASSAY PROCEDURE AND CALCULATION Two and one half grams of well-mixed sample was weighed (± 0.0001 g) into a 25-ml volumetric fl ask and mixed and diluted to volume with DMF. Two hundred fi fty micro- liters was transferred to an autosampler vial where it was mixed with 500 ml of BSTFA reagent. Two microliters was then injected into the GC and compared to 2-ml injections of the silylated standard mixture. Routine external standard calculations were used to determine percent DEG and EG.

JOURNAL OF COSMETIC SCIENCE 228 RESULTS AND DISCUSSION METHOD DEVELOPMENT A project was initiated here to develop an assay to confi rm that USP glycerin, USP pro- pylene glycol, USP sorbitol solutions, and incoming polyethylene glycol and polyethyl- ene glycol monomethyl ethers (Figure 1) did not contain DEG or EG adulteration. Since setting up fi ve to six separate test procedures for these materials at QC would be diffi cult due to space and instrument requirements, the need for a single, straightforward assay existed. A review of the literature found a TLC procedure for DEG and EG suggested by the FDA as an alternative to the USP monograph test (4), but this required followup GCMS confi rmation and quantitation (5), and thus would not be amenable to QC use. Two papers described an assay for trace ethylene glycol in used motor oil by GC (6,7). The author saw the opportunity to develop a single test method that would require less op- erator time, be amenable to automated analysis, and provide reliable quantitation. This laboratory has expertise in assaying similar materials, including DEG and glycerin, at low levels by capillary GC, and it was decided to evaluate that technique to see if it was amenable to all four of the raw materials stated above. Materials like these, with –OH (hydroxyl) functionalities, form strong internal hydrogen bonding, which makes volatil- ization and gas chromatography challenging, especially for materials with multiple hy- droxyl groups such as those detailed above. Because of this, derivatization using reagents such as BSTFA (bis[trimethylsilyl]-trifl uoroacetamide) can be used to improve volatilization Figure 1.