240 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 4. Prepare the following standards: 1.2, 1.0, 0.8 ppm by pipeting appropriate mls of working stock solution into volumetric flasks, and diluting to volume with Solvent A. Preparation of standard linearity curve for NDEIA.' 1. Start instrument and allow 15 min. to equilibrate using Solvent A. 2. Inject 25 3tl of Solvent A to check for any interference. 3. Inject (in triplicate) 25 3tl of the following standards: 1.2, 1.0, 0.8 ppm. 4. Record the peak height (cm) of each standard. 5. Take the average peak height of the standards and plot the peak height (cm) versus the concentration (ppm). A linear curve should be obtained. 6. Calculate slope and y-intercept of the linearity curve by a regression line analysis of the total standard data points. Sample preparation.' 1. Weigh 2.5--3.0 grams of sample into 10-ml volumetric flask. 2. Add 3 ml of Solvent A and swirl until sample dissolves, then dilute to volume with Solvent A. Determination of NDEIA in di- and triethanolamine: 1. Inject 25 3tl of Solvent A to check for any interference. 2. Inject 25 3tl of sample solution. Program the instrument after NDEIA peak is eluted (Refer to solvent program). 3. Record peak height (cm) of NDEIA in sample. 4. To determine the concentration (ppm) of NDE1A present in the sample solution, use the following equation: y=ax+b y = concentration of NDE1A (ppm) found in sample solution a = slope x = peak height (cm) b = y-intercept (a and b were calculated from standard NDEIA data points). 5. To determine total amount of NDE1A present in the original triethanolamine sample, use the following equation: Sample vol. ppm (original sample)= ppm (found) x Sample wt. C. METHOD OF ANALYSIS FOR LAURAMIDE DEA A Whatman (Partisil PXS 10/25 ODS) was used for the analysis, the remaining HPLC parameters used were the same as those for the analysis of the ethanolamines. Solvent Program.' a) Initial conditions--60% Solvent A/40% Solvent B (V/V). b) Hold time--5 min. c) Run time (initial condition to final condition)--3 min. d) Final condition--20% Solvent A/80% Solvent B (V/V).

NITROSAMINE ANALYSIS 241 e) Hold time--15-20 min. f) Reverse time (final condition to initial condition)--10 min. g) Final condition--60% Solvent A/40% Solvent B (allow approximately 30 min. for equilibration between runs). h) Programming is not needed for NDEIA standard runs, use initial condition (a). The preparation of NDEIA standards and the preparation of a standard linearity curve for NDEIA can be found under "Method of Analysis for Ethanolamines" in this experimental section, except that the diluting sovent is 60/40, water/methanol (V/V). Sample Preparation.' 1. Weigh 2.0-2.5 gm of sample into a 10-ml volumetric flask. 2. Add 3 ml of 60/40 water/methanol (V/V) and swirl until sample dissolves, then dilute to mark with 60/40 water/methanol. Determination of NDEIA in lauramide DEA.' 1. Inject 25/zl of 60/40 water/methanol to check for any interferences. 2. Inject 25/zl of sample solution. Program the instrument after NDE1A peak is eluted (refer to Solvent Program). 3. Record peak height (cm) of NDE1A in sample. 4. To determine the concentration (ppm) of NDEIA present in the sample, refer to Part 4 under "Determination of NDE1A in di- and triethanolamines" found in this experimental section. D. METHOD OF ANALYSIS FOR COCAMIDE DEA (USING A TWO COLUMN SEPARATION) HPLC parameters for initial separation of NDEIA.' Column/zPorasil, Waters Associates, 3.9 mm I.D. x 30.0 cm, stainless steel. Mobile phase--95%/5% chloroform/methanol V/V. Flow rate--l.O ml/min. Pressure (operating range)--O-6000 psi. Detector sensitivity--O.02 aufs. Recorder a) Range--10 mv. b) Chart speed--10 ram/min. HPLC parameters for NCEL4 quantitation on !aBondapak ( C•8).' Column/zBondapak (C•8). Flow rate--1 ml/min. Mobile phase--95%/5% water/methanol (V/V). Pressure (operating range)--O-6000 psi. Detector sensitivity--O.005 aufs. Recorder a) Range--10 mv. b) Chart speed--10 ram/min.