ANALYSIS OF 1,4-DIOXANE 283 Table I Gas Chromatographic Operating Conditions Column Temperature: Carrier: Air: Hydrogen: Valve Time to Backflush: Detector Temperature: Injector Temperature: Sensitivity: Attenuation: 70øC or appropriate temperature to efficiently separate 1,4-dioxane and chlorobenzene. Helium Carrier: 30 cc/min NORMAL VALVE POSITION Auxiliary: 30 cc/min NORMAL VALVE POSITION Carrier: 30 cc/min BACKFLUSH VALVE POSITION Auxiliary: 30 cc/min BACKFLUSH VALVE POSITION 300 cc/min 30 cc/min 125 seconds or appropriate time to efficiently separate 1,4-dioxane and chlorobenzene. 200øC 150øC Range: 10 -12 AFS Appropriate to keep 1,4-dioxane peak on scale. Co., Houston, TX. Operating conditions are listed in Table I. The 15-ft x 1/8-in column containing 25% TCEP (1,2,3-TRIS [2-cyanoethoxy] propane) on Supelcoport 80/100 mesh was purchased from Supelco Inc., Bellefonte, PA, and the 2.5-ft x 1/8-in column containing a 3:1 mixture of 10% SP2100 (or OV-IO1) on Supelcoport 80/100 mesh and 6% Carbowax 20M on Gas Chrom Q 80/100 was prepared in the laboratory using materials also purchased from Supelco Inc. CHEMICALS The solvent, chlorobenzene, was purchased from J. T. Baker Chemical Co., Phillips- burg, PA, and 1,4-dioxane was purchased from Chemical Samples Co. PREPARATION OF 1,4-DIOXANE STANDARD SOLUTIONS The standard solutions were prepared by making a stock solution of lg of 1,4-dioxane in 100g of chlorobenzene (1%). Then, the stock solution was diluted according to Table II Dilutions of the 1% 1,4-Dioxane in Chl•robenzene Stock Solution for the Preparation of Calibration Standard Solutions Diluted with Conc. Amount 1,4-Dioxane Solution Chlorobenzene to 3,000 1,000 300 100 30 10 5 1 mg/kg 3.0 g of 1% Solution 10 g mg/kg 1.0 g of 1% Solution 10 g mg/kg 3.0 g of 100o mg/kg Solution 10 g mg/kg 1.0 g of 100o mg/kg Solution 10 g mg/kg 3.0 g of 100 mg/kg Solution 10 g mg/kg 1.0 g of 100 mg/kg Solution 10 g mg/kg 0.5 g of 100 mg/kg Solution 10 g mg/kg 1.0 g of 10 mg/kg Solution 10 g

254 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II to obtain standard solutions with concentrations from 1 mg/kg to 10 g/kg (1%). All solutions containing 1,4-dioxane were handled in a ventilation hood. The standard curve was obtained by injecting 2/zl aliquots of each standard solution into the gas chromatograph using the conditions described in Table I. Four standard curves were drawn using peak height measurements for the 0-10, 10-100, 100-1000 and 1000-10,000 mg/kg ranges. Figure 2 shows the standard curve for 0-10 mg/kg range. Figure 3 shows the chromatogram obtained from the analysis of a 1 mg/kg standard solution. A different standard solution was analyzed each day to check the validity of the curve. PREPARATION AND ANALYSIS OF SAMPLES Three grams of sample were weighed into a 10-ml volumetric flask and diluted to the mark with chlorobenzene. The samples were analyzed by injecting a 2/zl aliquot into the gas chromatograph operated as described in Table I. After 120 s with the valve in the normal position, the valve is switched and the high boiling and non-polar components are backflushed (reverse flow) from the first column (SP2100 (or OV101)/Carbowax 20M mixed phase). At the same time, the low boiling and polar components, including 1,4-dioxane, are separated on the second, or analytical column (TCEP). The 1,4-dioxane peak height was measured and converted to concentration in mg/kg in the sample by using the appropriate standard curve. Figure 4 shows the gas chromatographic curve of an ethoxylate sample which was spiked with 5 mg/kg dioxane. 12 - Sample Size: 2•1 ..• 10 - Electrometer Range: 10 •2 AFS • E 8 E ß -• 6 e 4 2 0 2 4 6 8 10 1,4-Dioxane, mg / kg Figure 2. The 1,4-dioxane standard curve for the 0-10 mg/kg concentration range.